Ebook Principles of ambulatory medicine (7th edition): Part 1

(BQ) Part 1 book Principles of ambulatory medicine presents the following contents: Issues of general concern in ambulatory medicine, preventive care, psychiatric and behavioral problems, allergy and infectious disease, gastrointestinal problems, renal and urologic problems, hematologic problems, pulmonary problems.

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Ambulatory Medicine

S E V E N T H E D I T I O N

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Barker, Burton and Zieve’s

Ambulatory Medicine

Director, Medical House Staff Training Program Columbia University Medical Center

New York Presbyterian Hospital New York, New York

David E Kern, M.D., M.P.H.

Associate Professor of Medicine Johns Hopkins University School of Medicine Director, Division of General Internal Medicine Johns Hopkins Bayview Medical Center Baltimore, Maryland

Patricia A Thomas, M.D.

Associate Professor of Medicine Associate Dean for Curriculum Johns Hopkins University School of Medicine Baltimore, Maryland

Roy C Ziegelstein, M.D.

Professor of Medicine The Johns Hopkins University School of Medicine Executive Vice Chairman, Department of Medicine Director, Residency Program in Internal Medicine Johns Hopkins Bayview Medical Center

Baltimore, Maryland

Consulting Editors

L Randol Barker, M.D., Sc.M., M.A.C.P.

Professor of Medicine Johns Hopkins University School of Medicine Division of General Internal Medicine Johns Hopkins Bayview Medical Center Baltimore, Maryland

Philip D Zieve, M.D.

Professor of Medicine Johns Hopkins University School of Medicine Senior Advisor to the Medical Center

Johns Hopkins Bayview Medical Center Baltimore, Maryland

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6 th Edition c 2003 Lippincott Williams & Wilkins, 5th Edition c 1999 Lippincott Williams &

Wilkins, 4 th Edition c 1995 Williams & Wilkins, 3rd Edition c 1991 Williams & Wilkins, 2nd

Edition c 1986 Williams & Wilkins, 1st Edition c Williams & Wilkins

any form by any means, including photocopying, or utilized by any information storage and

retrieval system without written permission from the copyright owner, except for brief quotations

embodied in critical articles and reviews Materials appearing in this book prepared by individuals

as part of their official duties as U.S government employees are not covered by the

above-mentioned copyright.

Printed in the USA

Library of Congress Cataloging-in-Publication Data

Principles of ambulatory medicine / editors, L Randol Barker [et al.].—7th ed.

Care has been taken to confirm the accuracy of the information presented and to describe generally

accepted practices However, the authors, editors, and publisher are not responsible for errors or

omissions or for any consequences from application of the information in this book and make no

warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the

contents of the publication Application of the information in a particular situation remains the

professional responsibility of the practitioner.

The authors, editors, and publisher have exerted every effort to ensure that drug selection and

dosage set forth in this text are in accordance with current recommendations and practice at the

time of publication However, in view of ongoing research, changes in government regulations, and

the constant flow of information relating to drug therapy and drug reactions, the reader is urged to

check the package insert for each drug for any change in indications and dosage and for added

warnings and precautions This is particularly important when the recommended agent is a new or

infrequently employed drug.

Some drugs and medical devices presented in the publication have Food and Drug

Administration (FDA) clearance for limited use in restricted research settings It is the

responsibility of the health care provider to ascertain the FDA status of each drug or device

planned for use in their clinical practice.

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• C O N T R I B U T O R S •

Unless otherwise indicated, hospital appointments are at Johns Hopkins Bayview Medical Center, Baltimore, Maryland, and

faculty appointments are at the Johns Hopkins University School of Medicine.

Service

Frank C Arnett, Jr., M.D.

Professor of Internal Medicine

Division of Rheumatology and

Clinical ImmunogeneticsUniversity of Texas—Houston

Medical SchoolHouston, Texas

Bimal H Ashar, M.D., M.B.A.

Assistant Professor of Medicine

Paul G Auwaerter, M.D., M.B.A.

Associate Professor of Medicine

Jennifer E Axilbund, M.S., C.G.C.

Senior Genetic Counselor

Research Associate in Oncology

Carlos A Bagley, M.D.

Senior Resident of Neurosurgery

L Randol Barker, M.D., Sc.M., M.A.C.P.

Medical CenterRochester, New York

Linda F Barr, M.D.

Assistant Professor of Medicine

Pulmonary and Critical Care

Associates of BaltimoreTowson, Maryland

R Graham Barr, M.D., Dr P.H.

Florence Irving Assistant ProfessorDepartments of Medicine

and EpidemiologyColumbia University Medical CenterNew York, New York

O Joseph Bienvenu, III, M.D., Ph.D.

Assistant Professor of PsychiatryAssociate Director, AnxietyDisorders Clinic

James H Black, III, M.D.

Assistant Professor of SurgeryAttending Surgeon,

Vascular/Endovascular Surgery

David W Blodgett, M.D., M.P.H.

Adjunct FacultyDepartment of Health Policyand Management

Johns Hopkins Bloomberg School

of Public Health

David G Borenstein, M.D.

Clinical Professor of MedicineGeorge Washington UniversityMedical Center

Washington, D.C

Gary R Briefel, M.D.

Associate Professor of MedicineChief, Division of RenalMedicine

Robert E Bristow, M.D.

Associate Professor and Director

of Obstetrics and Gynecology

Director, ARVD Program

Nisha Chandra-Strobos, M.D.

Professor of MedicineDirector, CUUDirector, Clinical CardiovascularServices

The Johns Hopkins University School

of Medicine and Bloomberg School

of Public Health

Karan A Cole, Sc.D.

Assistant Professor of MedicineDivision of General Internal MedicineDirector, Med-Psych RotationDirector, JHU Faculty DevelopmentProgram and Teaching Skills

Eugene C Corbett, Jr., M.D.

Bernard B and Anne L BrodieProfessor of Medicine

Professor of NursingGeneral Medicines, Geriatrics, andPalliative Care

University of Virginia Health ScienceCenter

Charlottesville, Virginia

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Associate Professor of Psychiatry

Director, Center for Sexual Health

Professor of Clinical Medicine

Columbia University College of

Physicians and Surgeons

Director, Medical House Staff

Training Program

New York Presbyterian Hospital

Columbia University Medical Center

New York, New York

John A Flynn, M.D., M.B.A.

Clinical Director, Division of

General Internal Medicine

Associate Professor of Opthalmology

Wilmer Eye Institute

Ira M Garonzik, M.D.

Assistant Professor of NeurosurgeryDirector, Baltimore Neurosurgery andSpine Center

Steve N Georas, M.D.

Associate Professor of MedicineMedical Director, RespiratoryCare Department

Robert L Giuntoli, II, M.D.

Assistant Professor ofGynecology/ObstetricsAttending Physician, Department ofGynecology/Obstetrics

Uzma J Haque, M.D.

Assistant Professor of Rheumatology

John W Harmon, M.D.

Professor of SurgeryStaff Surgeon, Department

of Surgery

David B Hellmann, M.D., M.A.C.P.

Vice DeanMary Betty Stevens Professor

of MedicineChairman, Department of Medicine

H Franklin Herlong, M.D.

Glenn A Hirsch, M.D.

Instructor of Medicine,Division of Cardiology

Nathaniel W James, IV, M.D.

Assistant Professor of MedicineUniversity of Vermont College ofMedicine

Burlington, VermontAttending PhysicianMaine Medical CenterPortland, Maine

Roxanne M Jamshidi, M.D., M.P.H.

Assistant Professor ofGynecology/Obstetrics

Suzanne M Jan de Beur, M.D.

Assistant Professor of MedicineChief, Division of Endocrinology

Matthew L Kashima, M.D., M.P.H.

Assistant Professor ofOtolaryngology Head and NeckSurgery

Chief of Service, Department ofOtolaryngology Head andNeck Surgery

David E Kern, M.D., M.P.H.

Associate Professor of MedicineDirector, Division of GeneralInternal Medicine

Edward S Kraus, M.D.

Associate Professor of MedicineAssociate Medical Director,Adult Kidney Transplant Program

Bruce S Lebowitz, D.P.M

Instructor of Orthopedic Surgery

Frederick A Lenz, M.D., Ph.D.

Professor of NeurosurgeryAttending Neurosurgeon

Shari M Ling, M.D.

Assistant Professor of Rheumatologyand Geriatric Medicine andGerontology

Staff Clinician, Clinical ResearchBranch, NIA

Harbor HospitalBaltimore, Maryland

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Contributors vii

Mark C Liu, M.D.

Johns Hopkins Asthma and

Allergy CenterStaff Physician

Rafael H Llinas, M.D.

Assistant Professor of Neurology

Medical Director, Neurology Service

Associate Professor of Psychiatry

and Behavioral SciencesDirector, Anxiety Disorders Clinic

Simon C Mears, M.D., Ph.D.

Assistant Professor of

Orthopaedic SurgeryChief, Division of Total Joint

Arthroplasty and Trauma

Esteban Mezey, M.D.

Professor of Medicine

Myron Miller, M.D.

Professor of Medicine

Redonda G Miller, M.D., M.B.A.

Mack C Mitchell, Jr., M.D.

Director, Division of Gastroenterology

David N Neubauer, M.D.

Assistant Professor of Psychiatryand Behavioral SciencesAssociate Director, Johns HopkinsSleep Disorder Center

Gregory P Prokopowicz, M.D., M.P.H.

Assistant Professor ofMedicine

Michael J Purtell, M.D., Ph.D.

Assistant Professor ofOncology

Sheppard Pratt Health SystemTowson, Maryland

Annabelle Rodriguez-Oquendo, M.D.

Assistant Professor of MedicineDirector, Diabetes ManagementService

Larry N Scherzer, M.D., M.P.H., Sc.D

Department of PediatricsUniversity of ConnecticutEast Hartford, Connecticut

Chester W Schmidt, Jr., M.D.

Professor of PsychiatryChairman, Department ofPsychiatry and Behavioral Sciences

Stephen D Sears, M.D., M.P.H.

Adjunct Associate Professor ofCommunity and Family MedicineDartmouth Medical School

Chief Medical OfficerMaine General Medical CenterAugusta, Maine

Edward P Shapiro, M.D.

Professor of MedicineDirector, Noninvasive Cardiology

Philip L Smith, II, M.D.

Professor of MedicineProfessor, Asthma and Allergy Center

Sharon D Solomon, M.D.

Assistant Professor ofOphthalmology

Michael B Streiff, M.D.

Assistant Professor of MedicineMedical Director, AnticoagulationManagement Services

Patricia A Thomas, M.D.

Associate Professor of MedicineAssociate Dean for Curriculum

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viii Contributors

Varsha K Vaidya, M.D.

Assistant Professor of Psychiatry and

General Internal Medicine

Director, Consultation Liaison

Adjunct Professor of Environmental

and Occupational Health

George Washington University

Medical Director, Center to Protect

Workers Rights

Silver Spring, Maryland

Karen A Wendel, M.D.

Assistant ProfessorDivision of Infectious DiseasesUniversity of ColoradoHealth Science CenterDenver, Colorado

S Elizabeth Whitmore, M.D., Sc.M.

Associate Professor ofDermatology

John H Wilckens, M.D.

Assistant Professor ofOrthopaedicsChairman, Department ofOrthopaedics

Roy C Ziegelstein, M.D.

Professor of MedicineExecutive Vice ChairmanDirector, Residency Program inInternal Medicine

Philip D Zieve, M.D.

Professor of MedicineSenior Advisor

Acknowledgment

The Editors wish to acknowledge Ms Susan McFeaters, who has provided skillful and icated assistance on all editions of this book and, for the seventh edition, has become the Johns Hopkins administrative coordinator for the entire book.

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• C O N T E N T S •

Acknowledgment viii

Preface xv

Color Plate falls between Sections 16 and 17

3 The Practitioner–Patient Relationship and

Communication during Clinical

Encounters 25

L Randol Barker

4 Patient Education and the Promotion of

Healthy Behaviors 38

Karan A Cole and David E Kern

5 Complementary and Alternative Medicine 61

Bimal H Ashar

6 Sexual Disorders: Diagnosis and

Treatment 73

Leonard R DeRogatis, Arthur L Burnett, Linda C.

Rogers, Chester W Schmidt, Jr., and Peter J Fagan

Laura S Welch and David W Blodgett

9 Selected Special Services and Programs:

Disability Insurance, Vocational Rehabilitation, Family and Medical Leave Act,

and Home Health Services 137

L Randol Barker

10 Care of the Patient with Cancer 144

Michael J Purtell and Larry Waterbury

11 Adolescent Patients: Special

Considerations 153

Larry N Scherzer

12 Geriatric Medicine: Special

Considerations 177

Colleen Christmas and Thomas E Finucane

13 Care at the End of Life 192

Grace A Cordts, Thomas E Finucane, and Clare H Ferrigno

14 Integrating Prevention into Ambulatory

Practice 211

Gregory P Prokopowicz and David E Kern

15 Principles of Nutrition in Ambulatory

Care 228

Eugene C Corbett, Jr.

16 Exercise for the Healthy Patient 241

Ross E Andersen and Kerry J Stewart

17 Genetic Testing and Counseling 251

Jennifer E Axilbund and Constance A Griffin

18 Immunization to Prevent Infectious

Disease 261

William H Barker

PROBLEMS 277

19 Evaluation of Psychosocial Problems 279

Varsha K Vaidya and Chester W Schmidt, Jr.

20 Psychotherapy in Ambulatory Practice 286

Robert P Roca and L Randol Barker

21 Somatization 293

Robert P Roca

22 Anxiety and Anxiety Disorders 306

Una D McCann and O Joseph Bienvenu, III

23 Personality and Personality Disorders 324

Robert P Roca

24 Mood Disorders 329

Francis M Mondimore

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25 Schizophrenia and Related Psychotic

Disorders 349

Andrew F Angelino and Chester W Schmidt Jr.

26 Cognitive Impairment and Mental Illness in

33 Respiratory Tract Infections 474

Nicholas H Fiebach and R Graham Barr

34 Tuberculosis in the Ambulatory

37 Sexually Transmitted Diseases 538

Karen A Wendel and Jonathan M Zenilman

38 Lyme Disease and Other Tick-Borne

Illnesses 560

Paul G Auwaerter and John A Flynn

39 Human Immunodeficiency Virus

Infection 571

Darius A Rastegar and Michael I Fingerhood

40 Ambulatory Care for Selected Infections

Including Osteomyelitis, Lung Abscess, and

H Franklin Herlong and Mack C Mitchell, Jr.

43 Peptic Ulcer Disease 659

Mack C Mitchell, Jr and H Franklin Herlong

44 Abdominal Pain and Irritable Bowel

Syndrome 670

45 Selected Gastrointestinal Problems:

Constipation and Diarrhea 687

46 Selected Gastrointestinal Problems:

Gastrointestinal Bleeding, Colorectal Cancer Screening, and Diverticular

Disease 705

47 Diseases of the Liver 717

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59 Common Pulmonary Problems: Cough,

Hemoptysis, Dyspnea, Chest Pain, and

Abnormal Chest X-Ray 869

Irina Petrache and Steve N Georas

60 Obstructive Airway Diseases: Asthma and

Chronic Obstructive Pulmonary

62 Coronary Artery Disease 949

Nisha Chandra-Strobos and Glenn A Hirsch

63 Postmyocardial Infarction Care and Cardiac

65 Common Cardiac Disorders Revealed by

Auscultation of the Heart 1028

Susan A Mayer and Edward P Shapiro

68 Approach to Musculoskeletal Injuries 1125

Simon C Mears, John H Wilckens, and Ronald P Byank

69 Shoulder and Elbow Pain 1134

David E Kern

70 Neck Pain 1157

Carlos A Bagley, Ira M Garonzik, and Frederick A Lenz

71 Low Back Pain 1165

David G Borenstein

72 Knee, Lower Leg, and Ankle Pain 1183

John H Wilckens, Simon C Mears, and Ronald P Byank

73 Common Problems of the Feet 1201

Uzma J Haque and Joan M Bathon

78 Spondyloarthritis, Ankylosing Spondylitis,

and Reactive Arthritis 1280

John A Flynn and Frank C Arnett, Jr.

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84 Disorders of Bone and Mineral Metabolism:

Hypocalcemia, Hypercalcemia, Osteomalacia, Male Osteoporosis, Paget Disease of

Bone 1437

Suzanne M Jan de Beur

85 Male Reproductive and Sexual

Rafael H Llinas and Constance J Johnson

87 Headaches and Facial Pain 1484

Constance J Johnson

88 Seizure Disorders 1504

Peter W Kaplan

89 Dizziness, Vertigo, Motion Sickness,

Syncope and Near Syncope, and

Disequilibrium 1531

Jeffrey L Magaziner and Mark F Walker

90 Common Disorders of Movement: Tremor

and Parkinson Disease 1554

94 Peripheral Arterial Disease, Abdominal

Aortic Aneurysms, and Peripheral

Aneurysms 1634

James H Black, III

95 Lower Extremity Ulcers and Varicose

Veins 1649

Robert J Spence and Glen S Roseborough

96 Diseases of the Biliary Tract 1664

Esteban Mezey and John W Harmon

97 Hernias of the Groin and Abdominal

Wall 1673

John W Harmon and Christopher L Wolfgang

98 Benign Conditions of the Anus and

Rectum 1681

John W Harmon and Christopher L Wolfgang

101 Menstrual Disorders and Other Disorders of

Female Reproductive Endocrinology 1716

Meredith B Loveless and Shehzad Basaria

102 Nonmalignant Vulvovaginal Disorders, Pelvic Inflammatory Disease, and Chronic Pelvic

105 Diseases of the Breast 1770

Rima J Couzi and Michael J Purtell

106 Menopause and Beyond 1784

Degeneration 1799

Nada S Jabbur and Sharon D Solomon

108 Glaucoma 1808

David S Friedman

109 Diseases of the Eyelid, Conjunctiva, and

Anterior Segment of the Eye 1816

Robert S Weinberg

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Contents xiii

EARS, NOSE, THROAT, AND

ORAL CAVITY 1831

110 Hearing Loss and Associated Problems 1833

John K Niparko, Sara Love-Schlessman, and Howard W Francis

111 Selected Disorders of the Nose and Throat:

Epistaxis, Snoring, Anosmia, Hoarseness, and

Hiccups 1849

Matthew L Kashima

112 Common Problems of the Teeth and Oral

Cavity 1864

Douglas K MacLeod and David E Kern

115 Disorders of the Pilosebaceous Unit:

Acne and Related Disorders and

Hair Loss 1897

S Elizabeth Whitmore

116 Dermatitis and Psoriasis 1905

S Elizabeth Whitmore

117 Primary Superficial Fungal and Viral

Infections and Infestations 1914

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• P R E F A C E •

This book is directed to practitioners who care for

am-bulatory adult patients The purposes of the book are (a) to

provide an in-depth account of the evaluation,

manage-ment, and long-term course of common clinical problems

that are addressed in the ambulatory setting, and (b) to

provide guidance for recognizing problems that require

either referral for specialized care or hospitalization and

for appreciating the expected course of those problems

Three principles have guided the preparation of each

edition of Principles of Ambulatory Medicine.

1 Practitioners working in a busy practice need to know

about probabilities related to the occurrence, course,

evaluation, and treatment of their patients’ problems

2 The patient makes most decisions in ambulatory care,

and the quality of those decisions depends on the

patient–practitioner relationship and patient education.

3 The practitioner and the patient should incorporate a

preventive point of view into all actions taken to address

the patient’s health

With the seventh edition, Doctors Nicholas H Fiebach,David E Kern, Patricia A Thomas, and Roy C Ziegelstein

have become the Editors, and Doctors L Randol Barkerand Philip D Zieve have become Consulting Editors Allfour of the Editors served as Associate Editors for thesixth edition They played major roles in the expansion andreorganization of that edition, including the addition ofseventeen new chapters and many new authors

For the seventh edition, updating and revising of allchapters have been based on evidence from recent clini-cal trials, on current consensus-based recommendationsfor many conditions, and on the comments of those whohave used the book There are new sections on Bioterror-ism, the Family and Medical Leave Act, and eye surgeryfor refractive errors

Principles of Ambulatory Medicine is extensively

cross-referenced both to avoid redundancy and to facilitate cess to useful information contained elsewhere in thebook In addition, for easy reference, the key topics in eachchapter are presented in outline form at the beginning ofthe chapter For the seventh edition, Specific Referencescited in the text are listed at the end of each chapter, andGeneral References, many of them websites, are found atthe following internet address: www.hopkinsbayview.org/

ac-PAMreferences

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xvi

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5: Complementary and Alternative Medicine 6: Sexual Disorders: Diagnosis and Treatment 7: Sleep Disorders

8: Occupational and Environmental Disease and Bioterrorism 9: Selected Special Services and Programs: Disability Insurance, Vocational Rehabilitation, Family and Medical Leave Act, and Home Health Services

10: Care of the Patient with Cancer 11: Adolescent Patients: Special Considerations 12: Geriatric Medicine: Special Considerations 13: Care at the End of Life

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and Core Proficiencies

Temporal Dimension of Ambulatory Medicine 5

Core Proficiencies for Ambulatory Practice 8

Cost Containment and Managed Care 12

A fundamental tenet of this book is that ambulatory care

has distinctive characteristics that should shape

practi-tioners’ approaches to patients This chapter describes the

territory of ambulatory care in the United States, as well

as some of the proficiencies that are central to ambulatory

practice

THE TERRITORY OF AMBULATORY

PRACTICE

Who provides ambulatory care? What patients make

am-bulatory care visits? What problems do patients present at

their visits? What ambulatory care is provided for these

problems? To answer these questions, the United States

National Ambulatory Medical Care Survey (NAMCS),

started in 1973, has collected information periodicallyfrom a representative sample of physicians’ offices

Office-Based Practitioners

Table 1.1 shows the distribution by specialty of the proximately 890 million visits to physicians’ offices in theUnited States during 2002 Of these visits, 18% were to theoffices of internists and 24% were to the offices of general

ap-or family practitioners; 3% of all visits were to physician’sassistants or nurse practitioners (1) This book is directedprimarily to those physicians and other practitioners whoprovide primary care for adult patients

Ambulatory Patients

The NAMCS definition of an ambulatory patient is “an

in-dividual presenting for personal health services who isneither bedridden nor currently admitted to any healthcare institution.” A critical expansion of this definition

is that ambulatory or homebound patients (or members

of their households) have most of the responsibility forcarrying out their own care: They must administer treat-ments, monitor symptoms and functional status, adapt tothe constraints imposed by illness, and decide how to dealwith new problems when they arise These characteristicshave important implications for the care of ambulatorypatients, as discussed later in this chapter and throughoutthis book

Table 1.2 shows the age and sex distribution of the tients who made ambulatory visits to physicians’ offices in

pa-2002 In that year, the annual number of office visits byadults ranged from 1.8 for people 15 to 24 years old to 7.2for people age 75 years and older (1)

Problems of Ambulatory Patients

What types of problems are seen in ambulatory practice?

Using the International Classification of Diseases, 9th vision, Clinical Modification (ICD-9-CM), participants in

Re-NAMCS were asked to name the principal reasons for thevisits by patients Table 1.3 lists the 20 most common diag-noses named in 2002 Because comorbidity, especially thecoexistence of physical and mental morbidity, is very com-mon in ambulatory patients, this list of principal reasons

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4 Section 1 / Issues of General Concern in Ambulatory Medicine

◗TABLE 1.1 Number, Percent Distribution, and Annual Rate of Office Visits by

Selected Physician Practice Characteristics: United States, 2002

Physician Practice Number of Visits Percent Number of Visits per Characteristics in Thousands Distribution (%) 100 Persons per Year

All visits 889,980 100.0 314.4General and family practice 215,466 24.2 76.1Internal medicine 156,692 17.6 55.4

All other specialties 103,974 11.7 36.7

From Woodwell DA, Cherry DK National Ambulatory Medical Care Survey: 2002 Summary Advance Data for Vital and Health Statistics No 346 Hyattsville, MD: National Center for Health Statistics, August 26, 2004.

for visits tells only part of the story Furthermore, at least

half of ambulatory care visits are for symptoms, and a

diagnosis that explains these symptoms is infrequently

found (2) Ongoing research on common symptoms will

contribute critical information for addressing the needs of

ambulatory patients (see Kroenke and Laine, Investigating

Symptoms, at www.hopkinsbayview.org/PAMreferences).

Ambulatory Care

In 2002, ambulatory care for adult patients provided by

physicians who identified themselves as the patient’s

pri-mary care provider had the following general

characteris-tics (1):

Average number of visits per week 92

≥6 visits in past year (% of patients) 24%

Status of patient (% of visits)

Average number of drug mentions

per visit

2 drugs

Table 1.4 shows the proportion of ambulatory care visits

reimbursed by each of the primary sources of payment in

the United States for the year 2002

In addition to office visits, telephone and e-mail

encoun-ters and house calls are important in the care of ambulatory

patients Telephone and e-mail encounters enable

physi-cians and patients to handle many problems efficiently

(See Reisman and Stevens, www.hopkinsbayview.org/

PAMreferences.) Home visits are helpful for providing care

to patients who are too frail to make office visits and forlearning facts about patients’ home conditions that mayfacilitate management of their problems at future officevisits In 2002, primary care physicians practicing in theUnited States reported the following regarding nonofficeencounters with patients (1)

Office Telephone E-mail Home Visits Consultation Consultation Visits

Percent ofphysicians

Averagenumberper week

Self-Care and Alternative Care

Before making visits to physicians, patients usually tempt to diagnose and treat their own symptoms Addition-ally, in the past decade an increasing number of patients

at-in the United States report usat-ing one or more of the manytypes of complementary and alternative care medicinesthat are described in Chapter 5 (3)

Classic studies of self-care in a number of countriesshow that at any one time approximately 30% of personsare taking nonprescribed medications or are engaged inself-care for a problem for which they have not consulted

a physician (4) Over-the-counter (OTC) medications nowaccount for the majority of medicines taken in the UnitedStates (5) The frequency distribution of conditions man-aged by self-care was estimated by Fry (6), on the basis

of many years of general practice in a community well

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Chapter 1 / Ambulatory Care: Territory and Core Proficiencies 5

Annual Rate of Office Visits by Patient’s Age, Sex, and Race: United States, 2002

Patient’s Age (Years), Number of Visits Percent

Sex, and Race in Thousands Distribution (%)

75 years and over 115,049 12.9

Sex and Age

Under 15 years 76,382 8.615–24 years 44,909 5.025–44 years 128,743 14.545–64 years 144,205 16.265–74 years 61,819 6.9

Younger than 15 years 82,853 9.315–24 years 26,956 3.025–44 years 63,616 7.145–64 years 97,937 11.065–74 years 47,512 5.3

From Woodwell DA, Cherry DK National Ambulatory Medical Care Survey:

2002 Summary Advance Data for Vital and Health Statistics No 346.

Hyattsville, MD: National Center for Health Statistics, August 26, 2004.

known to him, as 25% upper respiratory tract infections,

20% musculoskeletal symptoms, 20% emotional problems,

10% acute gastrointestinal symptoms, 5% skin rashes, and

20% miscellaneous other symptoms Both the changing

status of drugs from prescription to OTC formulations and

the availability of herbal remedies without a prescription

(see Chapter 5) have expanded the “formulary” that

pa-tients can access for self-care

Table 1.5, adapted from NAMCS data, shows the timeinterval between the onset of a new problem and the

decision to go to a physician (i.e., the duration of

self-care) for a number of common conditions Not

surpris-ingly, patients with lacerations presented within 1 day,

pa-tients with symptoms of acute infection and chest pain

tended to present within 1 week, and patients with most

Diagnoses in Ambulatory Care Visits:

United States, 2002

Primary Diagnosis Number of Visits Percent Group in Thousands Distribution (%)

All visits 889,980 100.0Essential hypertension 48,180 5.4Routine infant or child

health check

35,935 4.0

Acute upper respiratoryinfections, excludingpharyngitis

30,141 3.4

Diabetes mellitus 24,877 2.8Arthropathies and

related disorders

23,725 2.7

General medicalexamination

22,362 2.5

Spinal disorders 20,444 2.3Rheumatism, excluding

back

17,766 2.0

Normal pregnancy 17,585 2.0Otitis media and

eustachian tubedisorders

16,702 1.9

Malignant neoplasms 15,651 1.8Chronic sinusitis 14,197 1.6Allergic rhinitis 14,101 1.6

Gynecologic examination 11,883 1.3Disorder of lipoid

other problems tended to present after at least 1 week ofself-care

Self-care before professional care is an important way

in which the patient, not the practitioner, makes the sions in the domain of ambulatory medicine The patient’sprimary role in carrying out the plan of care after an of-fice visit has already been emphasized These two featuresconfirm the primacy of the patient’s actions in determiningthe course of events in ambulatory medicine

deci-Temporal Dimension

of Ambulatory Medicine

The information from the NAMCS does not illuminate thelongitudinal nature of ambulatory care Table 1.6 shows

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Office Visits by Primary Expected Source of Payment: United States, 2002

Primary Expected Number of Visits Percent

Source of Payment in Thousands Distribution (%)

the 5-year profile of care for an elderly woman This

pa-tient’s story illustrates each of the following important

questions, for which only the passage of time provides the

answers:

■ What is the significance of a recent symptom (e.g., the

temporal headache for 1 year reported in 1975,

subse-quently not a serious problem)?

■ What is the advisability of initiating a referral for a

prob-lem (e.g., cataract identified but asymptomatic in 1975;

evaluated when more symptomatic in 1978 and

classi-fied as not mature)?

■ How well will the patient adhere to recommended

treat-ment (e.g., the digoxin prescribed in 1975 for heart

fail-ure, taken reliably for 5 years)?

■ What is the impact of a new treatment on the patient’s health (e.g., addition of a diuretic in 1978, with heart

failure gradually improving during the next month)?

■ What is the impact of intercurrent medical problems on the patient’s functional status? (The answer to this ques-

tion varied over time and was dependent on intercurrentproblems: Although the patient’s ambulation deterio-rated greatly during the 5 years, other valued activities,such as crocheting and canning, did not.)

■ What is the impact of the patient’s illness on family bers in the same household? (The answer to this question

mem-also varied over time; “exhaustion” at one point did notpredict transfer to a long-term care facility.)

Goals of Ambulatory Care

Patient Expectations

The goals of ambulatory care are strongly influenced bythe expectations of patients for their day to day activities inthe community When they make office visits, ambulatorypatients are seeking help to relieve symptoms or to cure,ameliorate, or prevent illness, so that they can maintain orresume valued activities Depending on the severity of theirproblems, outpatients may be greatly, moderately, or not atall constrained from attaining their expectations By virtue

of living in the community, they (or other caregivers) play

an active role in how these expectations are addressed, incontrast to the more passive role played by hospitalizedpatients

Implications for Practice

To determine how any patient is doing, it is helpful to beaware of the patient’s particular expectations and how wellthe patient is meeting them This usually involves learningabout the makeup of the patient’s current household and

Onset of Complaint or Symptom, According to Selected Principal Reasons for Visit: United States, 1977

Time Since Onset of Complaint or Symptom (days)

Principal Reason for Visit Total 1 1–6 7–21 30–90 >90 Not Applicable

All new problem visits 100.0 8.2 37.3 15.6 10.3 13.9 14.8

Laceration, upper extremity 100.0 70.4 15.4 7.8 3.0 2.1 1.3

From National Ambulatory Medical Care Survey: 1977 Summary Hyattsville, MD: National Center for Health Statistics.

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◗TABLE 1.6 Profile of 5 Years in the Care of an Elderly Patient

(each problem italicized )

Year

Encounters Initial visit, four office visits,

many phone calls

Three office visits,many phone calls

Five office visits, twohospital admissions,one home visit,many phone calls

Four office visits,many phone calls

Stable (digoxin) Stable (digoxin) Congestive heart

failure (diuretic

added)

Stable (digoxin,diuretic)

Degenerative joint disease (knees for years;

cervical spine for years)

Waxes and wanes(aspirin, Motrin)

Same (coated aspirin) Same (coated aspirin) Same (coated aspirin)

Temporal headaches for

1 year (erythrocytesedimentation rate, 30)

Rarely Rarely Rarely Rarely

Hearing loss (ear, nose,

and throat examination:

senile high frequencydeficit, no prescription)

Stable Stable Stable Stable

Bilateral cataracts Stable Stable Referred (not mature) Stable

Leukoplakia, mouth

(biopsy: not malignant)

Stable Stable Stable Referred for change in

appearance (biopsy:

not malignant)

Hematocrit, 35

(guaiac-negative)

Stable Stable Stable Stable

Constipation (for years) Waxes and wanes

(OTC laxative asneeded)

Same (OTC laxative

as needed)

Same (OTC laxative

as needed andstool softener)

Same (OTC laxative asneeded and stoolsoftener)

Leg cramps (quinine

at bedtime)

Minimal (quinine atbedtime)

Same (quinine atbedtime)

Left cerebral transient ischemic attack

Left CVA (hospital,

physical therapy)

Stable (righthemiparesis)

Recurrent left CVA

(home management)

Dog bite (cellulitis) No recurrence No recurrence

Rectal bleeding

(hospital, negativeworkup)

Family doing well

Painful toe Persists (codeine)

Appetite lost temporarily

No recurrence

Overall profile 87-year-old widow living

with daughter’s family,ambulatory andindependent in the home,mentally intact, crochetsand cans food; weight,166; multiple medicalproblems identified atinitial visit

88 years old, statusthe same; weight,160; two newproblems

89 years old,ambulation withwalker assistanceafter CVA; weight,151; four newproblems,hospitalized twice

90 years old, statusthe same; weight,140; three newproblems

91 years old;

ambulation moreimpaired aftersecond CVA;

mentally intact,crochets and cansfood; weight, 139; nonew problems

CVA, cerebrovascular accident; OTC, over-the-counter.

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◗TABLE 1.7 Factors to Consider in the Family Life

Cycle State of One’s Patient

Family Life Cycle State Developmental Tasks

Leaving home Differentiate self in relation to family

Develop intimate peer relationshipsEstablish oneself in work

Couples and pairing Form a committed relationship

Realign relationships with extendedfamily to include partnerPregnancy and childbirth Make room for children in the family

Become parents while remainingspouses

Family with young children Form a parent team

Negotiate relationships withextended family to includeparenting and grandparenting rolesFamily with adolescents Shift parent-child relationship to

permit adolescent to move in andout of system

Adulthood and middle years Refocus on marital and career issues

Deal with disabilities and death ingrandparents

Deal with own aging and mortalityGraying of the family Maintain functioning in face of

physiologic declineDeath and grieving Deal with loss of spouse, siblings,

and peersPrepare for own death

Adapted from Carter CA, McGoldrick M, eds The family life cycle: a

framework for family therapy New York: Gardner Press, 1980.

the patient’s usual role in the family, the patient’s

occupa-tion and level of formal educaoccupa-tion, and the patient’s valued

activities It is also helpful to be aware of the

developmen-tal tasks that may be relevant to a patient’s family Table

1.7 lists tasks that are typical of the various stages in the

life cycle of a family The significance of this information

can be illustrated by the common example of a

middle-aged man who has had an uncomplicated myocardial

in-farction After 3 months, the patient might be assessed as

“status postmyocardial infarction—doing well.” If he has

resumed work and other valued activities, then he is

prob-ably “doing well.” If he is not back at work, is financially

stressed, and his wife reports that he has become

irrita-ble, then he is not doing well and the situation requires

evaluation

Awareness of a patient’s life circumstances is

partic-ularly important in preventive care (see Chapter 14), in

which the patient’s degree of wellness, rather than degree

of illness, is assessed Assessing wellness means

deter-mining a patient’s goals, learning whether a patient

en-gages in health-promoting behaviors and identifying what

health risks the patient has For example, a 45-year-old

mother who seeks balance between her professional and

family life, is happily married, is free of chronic

dis-ease, has stopped smoking, has had periodic negative

Papanicolaou (Pap) smears, exercises regularly, and drinksalcohol only socially would be assessed as very well If ev-erything was the same except that the patient smoked twopacks of cigarettes daily, she would be assessed as onlymoderately well because of the major risk posed by heavytobacco exposure If she was feeling quite aimless, was re-cently divorced, had stopped seeing friends, and was smok-ing and drinking heavily, she would be assessed as not verywell, even though she might not complain of any particularsymptoms or have objective evidence of any disease

The approach to addressing the goals of ambulatory tients described here was recently summarized as shiftingone’s focus from a disease orientation to a focus on themeanings that patients attach to their illness, which typi-cally consists of multiple diseases and symptoms in chron-ically ill patients (7)

pa-CORE PROFICIENCIES FOR AMBULATORY PRACTICE

Information such as that provided by the NAMCS cussed earlier) has implications for several core proficien-cies needed in the practice of ambulatory medicine Thesecore proficiencies include medication prescribing, docu-mentation of care, coordination of care, discharge plan-ning, cost containment, evidence-based decision making,patient-centered communication, patient education andpromotion of healthy behavior, and integration of preven-tion into practice Chapters 2, 3, 4, and 14, respectively,address in depth the latter four areas

(dis-Medication Prescribing

Clinical pharmacology is the source for the many detailsneeded for appropriate prescribing of medications Apartfrom the impact of a medication on a patient’s condition,

it is important to be aware of the following aspects of eachdrug that one prescribes:

■ Practical information about initiating the drug:

appro-priate starting dosage and schedule; modifications indosage and schedule dictated by patient age, concur-rently administered drugs, and the presence of diseasesaffecting drug metabolism; time interval for the effects

of the drug to become apparent; duration of a course

of the drug (when not a maintenance drug); how to sess the impact of the drug; potential interaction withother drugs the patient is taking; approximate cost tothe patient of the drug; and whether the patient canafford it

as-■ The major side effects of the drug: when to anticipate them

and how to detect, monitor for, and manage them

■ The major reasons for inadequate response to a drug:

non-adherence, insufficient dosage of drug, antagonism ofthe drug by patient behavior or use of concurrent drugs,

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and primary refractoriness to the drug; how to recognizeand manage each of these problems

■ Practical information about adjusting the dosage:

mini-mum and maximini-mum dosages that can be tried and thetime intervals that are appropriate for adjusting dosagesand assessing impact

Because prescription of medications is the single mostcommon action taken by nonsurgical clinicians in ambu-

latory practice (see above), rapid access to this practical

information through published or electronic resources is

particularly important

Documentation of Care

Documentation of care in the ambulatory record serves

several purposes It provides for rapid access by

practi-tioners to the information they need for clinical decision

making at serial visits; justification of the level of care for

which payers are billed; and data accessibility for a

quality-of-care audit Documentation of care also stands as legal

evidence of a practitioner’s actions Both paper and

elec-tronic records can be designed to meet these purposes In

2002, approximately 18% of primary care physicians used

electronic clinical records (1) For a number of compelling

reasons, the implementation of electronic health records,

with connectivity between users, is regarded as a national

priority in the United States (8)

A well-structured primary care record, either paper orelectronic, includes the following components and infor-

mation:

■ A primary care front sheet (Fig 1.1) that includes a social

profile (information about the patient’s living situation,marital status, family makeup, occupation, education,social and recreational environment), a problem list that

is prominently displayed and facilitates awareness of thepatient’s problems, and other information that should

be readily findable, such as the patient’s allergic history,past hospitalizations and operations, and the status ofadvance directives

■ A treatment and clinical/laboratory flow sheet that is

prominently displayed and makes important past andcurrent information accessible for decision making (Fig

1.2)

■ A preventive care profile and flow sheet that documents

the patient’s risk factors (including family history of ness) and promotes the appropriate provision of peri-odic preventive care (for an example, see Fig 14.3)

ill-■ Encounter forms, including forms for telephone

encoun-ters, that allow clear documentation of information,thinking, and plans

■ Dividers, color-coded forms, and standardized locations

for various types of information such as consultants’

let-ters and laboratory reports, to increase the accessibility

of clinical data

To document patient education, prescriptions, andwork slips, it is helpful to use forms that make duplicatesfor mounting in the patient’s record

Coordination of Care

Another proficiency important in ambulatory practice isskill in coordinating the patient’s care Coordination ofcare refers to referral for, awareness of, and interpreta-tion of the services that a patient may need or receive Theavailability of many diagnostic and consultative servicesrequires generalists (1) to be prudent in recommendingthem and in using the information they provide, and (2) to

be aware of the cost of a service, the nature of the ence the patient will undergo, and the likelihood that theservice will be of value to the patient

experi-The services recommended for patients may involve manent, temporary, or partial transfer of responsibility forthe patient’s care (e.g., to a surgeon), or they may be strictlyconsultative, meaning that they provide information to beused by the referring physician or practitioner (rangingfrom diagnostic test results to a consultant’s suggestions)

per-Approximately 7.3% of office visits include referral of the patient to another physician (1) The following general

guidelines are important in coordinating the care of a tient who is referred for consultation:

pa-■ Assure that the necessary information is transmitted tothe person who will provide the service For example,there should be clear communication of the facts gener-ally needed by consultants (Table 1.8)

■ Ensure that the patient understands the reason for therecommended services, arrange to obtain informationpromptly after a service has been performed, and ensurethat the patient learns, as soon as it is appropriate, themeaning of this information

The finding in a 2003 survey that in one of seven primarycare office visits information critical for decision making

is missing, speaks to the challenge presented by the ordinating role of the generalist practitioner (9) As notedabove, the wider use of interconnected electronic clinicalrecords has the potential to greatly streamline this role

co-Patients sometimes obtain services for medical lems without referral by their personal physician Thesemost often include visits to emergency departments, tospecialists such as ophthalmologists, or to alternative prac-titioners (3) Being aware of these visits is another way

prob-in which generalists coordprob-inate their patients’ care Whenthey obtain services elsewhere, patients can play an essen-tial role by requesting that information be sent to theirpersonal physicians

Discharge Planning

Admission of the patient to the hospital follows imately 0.5% of office visits (1) For each admission,

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FIGURE 1.1.Example of a primary care front sheet

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FIGURE 1.2.Example of a clinical flow sheet, which aligns treatments and clinical/laboratory eters

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Consultants Generally Need from the Referring Physician

The specific reason for the consultation

Relevant current medical problems

Relevant current medications

Relevant diagnostic tests already completed

What the patient has been told about the referral

Patient’s attitude about the problem (if relevant)

Patient’s address or telephone number

hospital discharge usually means the return of the

pa-tient to ambulatory care by the papa-tient’s primary

physi-cian Each of the generic proficiencies described earlier

is especially important when patients make the transition

from dependence on hospital personnel to dependence on

themselves or their families for management of their

med-ical problems

Beginning with the implementation of the federal

pros-pective payment systems in the 1980s, and continuing with

the growth of managed care in the 1990s, very short

hospi-tal stays have become the norm in the United States By the

beginning of the 21st century, inpatient care by hospitalists

had become common and had been shown to add to the

efficiency of hospital care (10) These changes have drawn

attention to the elements of effective discharge planning,

such as ensuring that patients and their families have a

good understanding of the plan of care, ensuring that a

concise discharge summary goes promptly to the

practi-tioner or to the setting responsible for postdischarge care,

and using home health services or other community-based

services to help patients complete care that was previously

carried out during prolonged hospital stays Chapter 9

pro-vides detailed information about home health services

Cost Containment and Managed Care

Because of the extraordinary increase in available

medi-cal services in the past three decades and because of the

parallel increase in the cost and the use of these services,

cost containment in medical care is generally recognized

as a national imperative Managed care—that is, health

care in which delivery and financing of care are linked in

a variety of models—has emerged as a major strategy for

containing costs Managed care plans make arrangements

with physicians ranging from directly employing them

(staff-model HMOs) to contracting with them

association–model) (11) Based on the 2002 NAMCS datafrom primary care physicians, 40% have 3 to 10 and 35%

have more than 10 managed care contracts (1)

The goals of containing costs while providing quality care have critical implications for generalist physi-cians and practitioners, because it is they who coordinatemuch of the medical care provided in our society (12)

high-These goals can be addressed in a number of ways, cluding the following:

in-■ Taking a history carefully and allowing some time

to pass before embarking on an extensive diagnosticworkup of a new symptom;

■ Keeping well informed about the impact on health comes of costly diagnostic procedures and therapies;

out-■ Avoiding additional tests that will not alter one’s sions;

deci-■ Devoting sufficient time to educating patients abouttheir conditions (especially about conditions that oftenlead to inappropriate and costly doctor shopping by thepatient);

■ Prescribing only necessary medications and selectingthe least-expensive preparations;

■ Using home health services and other community vices, including innovative programs focused on high-cost conditions such as congestive heart failure, to fore-stall the need for hospital admission or to shorten thelength of hospitalization

ser-Before the era of managed care, fee-for-service bursement tended to foster excessive use of laboratorytests and costly procedures There were few external incen-tives for practitioners to engage in the inquiry, observation,counseling, and decision making that would have obviatedmuch inappropriate use of health services Besides foster-ing more appropriate spending of health care dollars, man-aged care may foster inappropriately low use of laboratorytests and costly procedures Fortunately, direct incentives

reim-to practitioners reim-to reduce the use of such services havebeen banned in most settings To the extent that managedcare rewards physicians for cognitive services—and doesnot overburden them with administrative hurdles or forceupon them unreasonable productivity expectations—it hasthe potential both to promote the health of patients and toreduce the unnecessary use of costly services

SPECIFIC REFERENCES

1 Woodwell DA, Cherry DK National Ambulatory

Medical Care Survey: 2002 Summary Advance

Data for Vital and Health Statistics No 346.

Hyattsville, MD: National Center for Health

Statistics, August 26, 2004.

2 Kroenke K Studying symptoms: sampling and measurement issues Ann Intern Med 2001;

134:844.

3 Eisenberg DM, Davis RB, Ettner SL, et al.

Trends in alternative medicine use in the United

States, 1990–1997 JAMA 1998;280:1569.

4 Kohn R, White KL, eds Health care New York:

Oxford University Press, 1976.

5 Google Fact Sheet, 2005 The Use of Counter Medicines.

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Chapter 2 / Practicing Evidence-Based Medicine 13

6 Fry J Common diseases: their nature, incidence

and care 2nd ed Philadelphia: Lippincott, 1979.

7 Tinetti ME, Fried T The end of the disease era.

Am J Med 2004;116:179.

8 Institute of Medicine, Committee on the Data

Standards for Patient Safety Key Capabilities

of an Electronic Health Record System.

Washington, DC: Institute of Medicine, 2003.

9 Smith PC, Araya-Guerra R, Bublitz C, et al.

Missing clinical information during primary care visits JAMA 2005;293:565.

10 Wachter RM, Goldman L The hospitalist movement 5 years later JAMA 2002;287:487.

11 Gold MR, Hurley R, Lake T, et al A national

survey of the arrangements managed-care plans make with physicians N Engl J Med 1995;333:

1678.

12 Bodenheimer T, Fernandez A High and rising health care costs Part 4: can costs be controlled while preserving quality? Ann Intern Med 2005;

Clinicians are increasingly (and appropriately) asked to

provide both scientifically sound and cost-effective

medi-cal care These expectations have given rise to an emphasis

on evidence-based medicine (EBM), which is defined as the

conscientious, explicit, and judicious use of current best

evidence in making decisions about the care of individual

patients (1) EBM focuses on issues integral to day-to-day

patient care: assessment of risks, prevention, screening,

diagnosis, prognosis, treatment, and management of the

increasing amount of medical information that confronts

health care practitioners

Evidence-based decision making is especially tant in ambulatory practice because this is the setting

impor-∗ Scott M Wright contributed to an earlier version of this chapter.

where patients are most likely to present with tiated problems It is also the setting where most clinicaldecisions are made

undifferen-The following steps are considered to be indispensable

to practicing EBM:

Step 1: Formulate specific questions that are relevant to apatient’s care and identify the type of information that isneeded (e.g., efficacy or harm of a treatment, accuracy

of a diagnostic test)

Step 2: Identify and retrieve the relevant data

Step 3: Critically appraise the relevant information

Step 4: Apply the valid information to the patient whosepresentation initiated the inquiry, taking into accountthe patient’s values and wishes

The importance of step 1, formulation of specific

tions, can be understood by considering two similar tions that might be generated when a practitioner sees apatient with hepatitis C who asks whether antiviral ther-apy, which the patient has read about in the newspaper,should be initiated:

ques-■ Question A: How effective is interferon and ribavirin forthe treatment of hepatitis C?

■ Question B: For Mr B, the 48-year-old man with type 2hepatitis C whose transaminases and liver function testshave been normal during the last 9 months, what is theevidence regarding the efficacy and safety of interferonand ribavirin in preventing cirrhosis and other compli-cations?

The second question is more specific and will better help

to tailor the search effort (step 2) to the clinical outcomesthat are most relevant to the practitioner and the patient

The successful completion of step 2 requires efficient

and effective searching skills Most medical libraries fer brief hands-on tutorials to teach clinicians how tosearch databases such as MEDLINE and the Internet tofind the current best evidence The National Library ofMedicine (see www.hopkinsbayview.org/PAMreferences)provides access to PubMed (MEDLINE) and multiplehealth and science databases It also offers full-text ver-sions of many articles, eliminating the need for additionalsteps to retrieve the desired manuscripts

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Step 3, critical appraisal, is likely to be most difficult

and time-consuming for clinicians The two components

of this step are (a) deciding whether the results are valid and

(b) deciding whether the results are relevant to the specific

question being asked

It is more efficient to resolve the second component

first, which can usually be done fairly quickly If the

re-sults are neither relevant nor clinically important, then

one can avoid the time and effort spent judging the

va-lidity and quality of the information There are numerous

books and articles published in the medical literature (e.g.,

the Users’ Guides to the Medical Literature series

pub-lished by the Journal of the American Medical Association)

that aim to teach clinicians the core skills of critical

praisal Having confidence in one’s ability to critically

ap-praise manuscripts on a wide variety of topics (e.g.,

diagno-sis, treatment, cost-effectiveness), and which use a myriad

of study designs, may take time, practice, and even

addi-tional training Such training can be found in workshops

at regional and national meetings or through medical

libraries

Step 4 involves integrating the important and valid

newly found information into the care of one’s patient

This step can be the most satisfying component of

practicing EBM Educating patients that a particular

di-agnostic approach or treatment is supported by current

medical research may instill a sense of confidence about

the practitioner’s knowledge and expertise in finding new

data However, even after completing all these steps,

choos-ing the best course of action is not always straightforward,

and the patient’s values and wishes should determine the

ultimate course of action For example, a patient may wish

to forgo a treatment that may prolong their life but will

likely worsen their quality of life (e.g., chemotherapy for

metastatic cancer) or a patient may be unwilling to trade

a short-term risk for the possibility of a long-term

bene-fit (e.g., carotid endarterectomy for asymptomatic carotid

stenosis)

It would be impractical to assume or recommend that

primary care practitioners embark on these fundamental

steps of EBM every time a clinical question comes up

However, when critical queries arise that are likely to recur

or are particularly important to an individual patient, this

version of “self-directed continuing medical education” is

likely to be helpful to both practitioners and patients Some

barriers to practicing EBM include skepticism by

practi-tioners, information overload and feeling overwhelmed by

the growth of medical knowledge, lack of time, and lack of

appropriate resources, skills, or motivation to implement

EBM (2) Furthermore, for some clinical questions,

high-quality data is lacking

All dedicated and committed clinicians, however,

prac-tice EBM to some degree To counterbalance the barriers to

practicing EBM, the following facilitating behaviors have

been proposed: (a) reading and keeping up-to-date with themedical literature (see Keeping Up); (b) refining one’s EBMskills (practice makes perfect); (c) collaborating with col-leagues so that valuable clinical evidence is shared amongpractitioners; (d) writing down specific clinical questions(step 1) when they come up so that the process can con-tinue when time permits; (e) setting up one’s computer(e.g., bookmarking relevant websites) and one’s office (e.g.,acquiring access to high-quality information) so as to findinformation efficiently; and (f) making friends with thelibrarian at the nearest medical library

The remainder of this chapter discusses the core ples of EBM that apply to issues most relevant to primarycare practice: diagnosis, prognosis, treatment, risk or po-tential harm, and cost-effectiveness Strategies for keeping

princi-up are also discussed Chapter 14 discusses principles thatapply to prevention and screening

DIAGNOSIS How Clinicians Formulate a Diagnosis

Diagnostic assessment begins the moment one meets apatient Behavioral scientists have described at leastfour ways in which clinicians formulate diagnoses: pat-tern recognition, algorithm, exhaustion, and hypothesis-deduction

Pattern Recognition

Many diagnoses are made instantly because clinicianshave learned to recognize patterns specific to certain dis-eases, such as the face of a patient with Down syndrome

or the elbows of a patient with psoriasis The certainty

of these types of diagnoses is so great that further testingoften is unnecessary

Algorithm

Algorithms are growing more common as a result ofthe growth of clinical practice guidelines, which, whengrounded scientifically, can be extremely helpful Thedrawbacks of algorithms are that they must be constructedbefore the patient is seen, and they must account for everypossibility in a workup

his-to do one again On occasion, however, clinicians do resort

to comprehensive histories and examinations, as much tobuy time to think as to uncover hidden disease

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Hypothesis–Deduction

Clinicians usually diagnose by forming hypotheses and

testing them, as is done in scientific experimentation On

hearing that a patient has chest pain, the practitioner

builds a short list of hypotheses, invites further

descrip-tion, and then asks focused questions that help confirm

or rule out the hypotheses The questions in the interview

and each maneuver in the examination are as much

diag-nostic tests as the electrocardiogram or the chest

radio-graph Studies of clinicians’ behavior reveal that the short

list of hypotheses usually does not exceed three or four

diagnoses Typically, new hypotheses are added as others

are discarded, but the eventual goal is to narrow the list

and reduce the uncertainty about which diagnosis is most

likely Studies of clinicians in ambulatory practice showed

that hypotheses were generated, on average, 28 seconds

into the interview, and that correct diagnoses of standard

problems were made 6 minutes into 30-minute workups;

the correct diagnoses were made in 75% of the

encoun-ters (3)

The hypothesis–deduction model reveals a truth mon to all methods of diagnosis: Rarely can a clinician

com-be absolutely certain of any diagnosis Clinicians live with

uncertainty, and the role of all diagnostic tests—the

inter-view, the physical examination, the laboratory evaluation,

trials of empiric treatments, allowing time to pass

(expec-tant observation)—is to narrow the uncertainty enough to

place a diagnostic label on a patient’s problem How

nar-row the uncertainty must be depends on the practitioner’s

and the patient’s tolerance of uncertainty, the severity of

the suspected disease, the “treatability” of the suspected

disease, and the benefits and risks of possible treatments

Steps in the Hypothesis–Deduction

Process

Evidence shows that clinicians implicitly use common

sense and their medical knowledge to reach a diagnosis

with adequate certainty Explicitly, the diagnostic process

follows certain steps

Step 1: Form a Hypothesis and

Estimate Its Likelihood

The estimate of likelihood is called the pretest probability

(or prior probability); it simply represents the estimate of

prevalence of the disease in a group of people similar to

the patient at hand Each hypothesized diagnosis and the

estimate of its likelihood comes initially from evidence

col-lected during the interview and physical examination and

from the practitioner’s fund of knowledge from sources

such as other patients, colleagues, textbooks, and journals

More recently, computer programs have been developed to

aid clinicians in making this estimate; these programs havethe potential to become a powerful tool in clinical decisionmaking

Step 2: Decide How Certain the Diagnosis Must Be

If the hypothesized disease is easily and safely treated, onemight have to be less certain than if the disease has an omi-nous prognosis or demands complex, risk-laden treatment

For example, a 75% certainty that a patient has ccal pharyngitis might be sufficient to prescribe an antibi-otic, whereas a much higher level of certainty is neededbefore diagnosing and treating a patient with suspectedleukemia If the pretest probability is above the thresholdfor a hypothesized disease (e.g., greater than 75% for strep-tococcal pharyngitis), further tests are unnecessary andtreatment is prescribed Conversely, if one is adequatelycertain that the patient does not have the hypothesized dis-ease (e.g., 90% probability that the patient does not havestreptococcal pharyngitis), no further tests are requiredand the patient can be reassured and educated However,

streptoco-if the level of uncertainty remains between these two tremes, further testing (e.g., a throat culture) can helpmove the case toward one extreme or the other Diagnostictesting usually is most helpful between the two extremes

ex-of certainty, whereas further testing generally has little pact on the posttest probability if the pretest probability isvery high or very low

im-Step 3: Choose a Diagnostic Test

Which test to choose depends on many factors, including

its safety, its accuracy (e.g., how closely an observation or

a test result reflects the true clinical state of a patient),how easily it can be done, its cost, and, not least, the pa-tient’s preferences and values regarding tests, especiallythose that carry risks Accuracy includes both reliability

and validity Reliability of a test, also called reproducibility

or precision, is the extent to which repeated measurements

of a stable phenomenon give results close to one another

Validity is the degree to which a test measures what it is

supposed to measure A test can be reliable but not valid(i.e., it reliably measures the wrong phenomenon), or it can

be valid but not reliable (i.e., it measures the phenomenon

of interest, but with wide scatter)

When considering a test, one needs to reflect on each

of these factors Table 2.1 summarizes practical guidelines

to assess and critically appraise reported studies of nostic tests When selecting a test for a patient, the crucialquestions to ask are, “Will the results of the test change

diag-my plan?” and “Will diag-my patient be better off from having

had the test?” (the utility of the test) If the answer to these

questions is “No,” the test should not be performed

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Diagnostic Test

Was there an independent blind comparison with a gold standard?

Was the test evaluated in a sample of patients that included an

appropriate spectrum of disease (mild to severe, treated and

untreated) plus patients with commonly confused disorders?

Was the setting for the evaluation adequately described?

Were the reproducibility of the test result (precision) and its

interpretation (observer variation) determined?

Was the term normal defined sensibly?

Were the methodologies for conducting the test described well

enough for their exact replication?

Was the utility of the test determined (i.e., were the patients better

off for having had the test)?

Adapted from Sackett DL, Haynes RB, Guyatt GH, et al Clinical

epidemiology: a basic science for clinical medicine 2nd ed Boston: Little,

Brown, 1991.

Step 4: Be Aware of the Test’s

Performance Characteristics

Every diagnostic test has a sensitivity and specificity for

each disease it tests for Sensitivity and specificity have

become common terms in medical discussion, but they

are often misunderstood The sensitivity of a test (the true

positive rate) is equal to the number of study subjects with

a given disease who have a positive test divided by all study

subjects with the disease The specificity of a test (the true negative rate) is the number of study subjects without the

disease who have a negative test divided by all those out the disease The 2× 2 table in Fig 2.1 reveals muchabout these and related terms

with-Tests with high sensitivity have a low false-negative rateand are useful for “ruling out” a diagnosis (when they arenegative) Conversely, tests with high specificity have a lowfalse-positive rate and are useful for “ruling in” a diagnosis(when they are positive) One way of remembering this

is with the mnemonics SnNOut (high sensitivity, negativeresult rules out) and SpPIn (high specificity, positive resultrules in) However, it should be pointed out that these rules

of thumb do not always hold up in actual practice; theability of a sensitive test to rule out a diagnosis is reducedwhen the specificity is low (4)

“Diseased” and “not diseased” are labels that reflect abest test or a definition of a certain disease: the so-called

gold standard For pulmonary embolus, for example, the

gold standard is the pulmonary angiogram For angina,there is no sure test, so a case definition becomes thegold standard Skepticism must be used in evaluating gold

Assessment of iron stores in bone marrow of anemic patients

FIGURE 2.1.Test performance

determined by research

Resear-cher identifies diseased and

non-diseased patients using a gold

standard and then determines

the performance characteristics

(sensitivity and specificity) of

another test Example:

Iron-deficiency anemia

determina-tion using bone marrow

aspi-rate/biopsy as the gold standard

and serum ferritin measurement

as the screening test (Data from

Guyatt GH, Patterson C, Ali M,

et al Diagnosis of iron

defi-ciency in the elderly Am J Med

1990;88:205.)

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Iron-Deficiency Anemia: Likelihood Ratios

Serum

to be Used as False-Negative False-Positive Likelihood Ratio Likelihood Ratio

the Cutoff Sensitivity Rate (1− Specificity Rate (1− (sensitivity/false- (false-negative

Value (μg/L) (%) sensitivity, %) (%) specificity, %) positive rate) rate/specificity)

Adapted from Guyatt GH, Patterson C, Ali M, et al Diagnosis of iron deficiency in the elderly Am J Med 1990;88:205, and

from Sackett DL, Haynes RB, Guyatt GH, et al Clinical epidemiology: a basic science for clinical medicine 2nd ed.

Boston: Little, Brown, 1991.

standards, for they often have their own limitations For

example, when gallbladder ultrasonography was tested for

use in the diagnosis of cholelithiasis, it initially seemed

to be a poor test in comparison with the gold standard

(oral cholecystogram), not because of problems with the

new test, but because, as was later shown, the gold

stan-dard was itself a poor test (5) Studies of diagnostic

test-ing may have other problems, includtest-ing verification bias

(when those with a positive test result are more likely to

have further evaluation), spectrum bias (when the

popula-tion tested does not reflect those in whom the test will be

used), and incorporation bias (when the results of the test

under study are included among criteria to establish the

reference standard)

Sensitivity and specificity are not static properties of a test As the cutoff value for an abnormal result is made

more extreme, the test’s sensitivity decreases and its

speci-ficity increases Table 2.2, where progressively lower

fer-ritin levels are used to characterize elderly patients as

hav-ing iron-deficiency anemia (IDA), illustrates this principle

(6) This illustration matches the common-sense

conclu-sion that as a patient’s test result becomes more abnormal,

one can be more certain that the patient has disease—

although never fully certain If one selects a very low

fer-ritin level for the cutoff between normal and abnormal

(Table 2.2), many iron-deficient people will remain

undi-agnosed (i.e., the sensitivity will be low), but almost all of

those diagnosed will be truly iron deficient (i.e., the

speci-ficity will be high) Conversely, if one decides to label

pa-tients as having IDA based on a ferritin level well within

the normal range (e.g., 75μg/L), one will not miss much

disease (higher sensitivity), but will falsely label numerous

anemic patients as being iron deficient who are not (lower

specificity) When interpreting the results of a test, a

clin-ician must consider the severity of disease, the potential

risks and benefits of treatment, and changing information

about the risks and benefits of treatment

Another way of showing the relationship (and

trade-off) between sensitivity and specificity is to plot a receiver

operating curve (ROC); the true-positive rate (sensitivity)

is plotted on the vertical axis and the false-positive rate(1− specificity) on the horizontal axis Figure 2.2 shows aplot of the values provided in Table 2.2 Receiver operatingcurves can be a useful tool to compare different diagnostictests; in general, the closer the curve is to the left-upper-hand corner (100% sensitivity and specificity), the betterthe test performs

Step 5: Determine a Posttest Probability of Disease

The perfect test (100% sensitivity and specificity) wouldyield a “yes” or “no” answer to the question “Does my pa-tient have disease or not?” However, because no test is per-fect, the more appropriate question is: “Given the result ofthis test, what is the posttest probability that my patienthas (or does not have) disease?” Posttest probability takesinto account both the performance characteristics (sen-sitivity and specificity) of the test and the pretest (prior)probability of disease in a group of patients similar to thepatient in question

<15

<35

<65 <95

0 10 20 30 40 50 60 70 80 90 100

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One method for determining posttest probability is

through the use of predictive values Predictive values

can be calculated from the known sensitivity and

speci-ficity of a test and the estimated pretest probability of

disease Sensitivity and specificity are generally

transfer-able from study to practice settings, provided the

dis-eased and nondisdis-eased populations in the study and in

the practice settings are similar Sensitivity and

speci-ficity usually are not influenced by the prevalence, or

pretest probability, of disease However, predictive

val-ues must be recalculated for each patient or population

from the estimated pretest probability or prevalence of

disease in that particular group Positive predictive value

is the probability of disease in a patient who has an

ab-normal test result Negative predictive value is the

proba-bility of no disease in a patient for whom a test result is

normal Figure 2.1 illustrates the calculation of posttest

probability, based on pretest probability, sensitivity, and

specificity

The lower the pretest probability of disease, the lower

the positive predictive value of a test, the lower the posttest

probability of disease, and the more likely it is that a

positive test result is falsely positive This influence of

pretest probability on posttest probability makes intuitive

sense For example, when a seasoned clinician encounters

an unexpected positive test result in a patient with a very

low likelihood of disease, the clinician is suspicious of the

finding and either repeats the test, suspecting laboratory

error, or orders another, more specific test to confirm or

refute the finding

Published information is available that can be helpful in

estimating pretest probability, and therefore the predictive

value of test results, in patients with selected

characteris-tics Examples of how such information can be used to

interpret test results and determine diagnostic strategies

are illustrated elsewhere in this book for deep vein

throm-bosis (see Chapter 57) and renovascular hypertension (see

Chapter 67)

Another method of calculating posttest probability of

disease is through the use of a likelihood ratio (LR).

This number combines the relationships of sensitivity and

specificity into a single number The positive LR (+LR)

is the true-positive rate (sensitivity) divided by the

false-positive rate (1− specificity), and the negative LR (–LR)

is the false-negative rate (1 − sensitivity) divided by the

true-negative rate (specificity) LR ranges from 0 to

infin-ity; when the positive LR is between 0 and 1, a positive test

result decreases the posttest probability; when it is >1, it

increases the posttest probability; a LR of 1 does not change

the posttest probability (i.e., the test is not useful)

There are a few ways of using the LR to calculate

posttest probabilities The standard method is to convert

pretest probability into an odds ratio, multiply this by the

likelihood ratio to determine posttest odds ratio, and then

convert the posttest odds ratio to a probability:

FIGURE 2.3.Nomogram for interpreting test results using

like-lihood ratios Example from text: An elderly male patient with

anemia has a pretest probability of having IDA equal to 33% Hisserum ferritin level is 33μg/L, which is associated with a positive

LR of 14.3 Extending a straight line through the pretest bility of 33% and the LR of 14.3 results in a posttest probability

proba-of 88% (Adapted from Fagan TJ Nomogram for Bayes’ theorem

N Engl J Med 1975;293:257.)

1 Pretest Probability÷ (1 − Pretest Probability) = PretestOdds

2 Pretest Odds× Likelihood Ratio = Posttest Odds

3 Posttest Odds÷ (1 + Posttest Odds) = Posttest bility

Proba-Another method is to use a nomogram (Fig 2.3) thatallows conversion of pretest to posttest probabilities, given

a known LR, without having to convert back and forthbetween probabilities and odds This alternative is quick,

is easy to use, and decreases the chances of calculationerror

However, converting probabilities to odds ratios andback can be cumbersome, and most of us do not carrynomograms in our pockets For this reason, it may be sim-pler to use a method of estimating posttest probabilities(7) This method is fairly accurate when the pretest prob-ability is between 10% and 90% (i.e., neither very high norvery low) Table 2.3 summarizes the approximate change

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◗TABLE 2.3 Simplified Posttest Probability

Estimates Based on Likelihood Ratio∗

Approximate Change Likelihood Ratio in Probability

From McGee S Simplifying likelihood ratios J Gen Intern Med 2002;17:646.

in probability associated with a range of LRs One can

sim-ply remember that positive LRs of 2, 5, 10 are associated

with approximate posttest probability increases of 15%,

30% and 45% respectively Conversely, LRs of 1/2 (0.5),

1/5 (0.2), and 1/10 (0.1) decrease the posttest probability

by 15%, 30% and 45% respectively

For example, suppose the clinician is faced with a year-old male patient who has increasing fatigue and is

67-found to be anemic Knowing that the baseline prevalence

(pretest probability) of IDA among anemic elderly patients

is 31% (6), one might consider this man’s pretest

probabil-ity of IDA to be approximately 33%, for an odds of 1:2, or

0.5 If the serum ferritin is 33μg/L, we can see from Table

2.2 that when a cutoff of<35 μg/L is used, the positive LR

patient has a posttest probability of IDA of about 7 ÷

(1 + 7) = 7 ÷ 8 = 88% Given this posttest probability,

further diagnostic workup (e.g., colonoscopy) to identify

the cause of the IDA is appropriate

Using the nomogram and a straightedge, the posttestprobability is approximately 85% Finally, if we use the

simplified estimation method outlined earlier, we know

that the likelihood ratio is>10; consequently, we should

add at least 45% to the pretest probability of 31%, yielding

a posttest probability of>76%, which is probably close

enough to the actual value to help us in our decision

making

PROGNOSIS

Often, the information that is most important to a patient

who has a new diagnosis is the prognosis (“What is going

to happen to me?”) In choosing therapy, one decides whatone can do for the patient’s disease Yet, predicting whatwill happen to a particular patient usually is not possi-ble, and clinicians must rely on probabilities Sometimes,specific characteristics (“prognostic factors”) such as de-mographic factors, disease-specific factors, and comor-bidities can help further delineate a patient’s progno-sis Clinical prediction rules that take these factors intoaccount can help practitioners arrive at more accurateestimates of prognosis

Prognosis can be addressed in two ways: the ural history of a disease and the clinical course of a

nat-disease Because few diseases today progress without ical intervention, less is being learned about natural his-tory and more is being learned about clinical course

med-For example, the natural history of diabetes in the late20th century is unknown because virtually no diagnosedpatients go without some type of therapy, yet throughmany studies, more is known about the course of treateddiabetes

Most information about prognosis comes from tive cohort studies in which patients with a disease aremonitored over time Cohort studies may include only un-treated subjects (natural history of a disease), only treatedsubjects, or a combination of both treated and untreatedsubjects (clinical course of a disease) Cohort studies aresimple in design, yet they are often costly in time and

prospec-money They are susceptible to biases, such as sampling bias, in which the group of patients being monitored is not

representative of all patients with that condition Table 2.4summarizes suggested guidelines for assessing studies ofprognosis

TREATMENT

Once a diagnosis is made, treatment becomes the focus

of care Before embarking on a treatment plan, one mustdecide on the goals of treatment (to cure, delay complica-tions, relieve acute distress, reassure, or comfort) Clearly,more than one goal may be chosen For example, when

of Prognosis

Was a representative and well-defined sample of patients (at asimilar point in disease course) assembled?

Are these patients similar to my own?

Was followup sufficiently long and complete?

Were objective and relevant outcome criteria developed and used?

Was the outcome assessment “blind”?

Was adjustment for important prognostic factors carried out?

Adapted from Laupacis A, Wells G, Richardson WS, et al User’s guides to the medical literature V: how to use an article about prognosis JAMA 1994:272:234.

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diagnosing and treating type 2 diabetes, one may seek to

cure (counsel weight loss and exercise), to delay or prevent

complications (seek tight glucose control), and to relieve

distress, reassure, and comfort (listen to the patient’s fears,

reassure the patient that diabetes is a treatable disease and

that he or she will not be abandoned)

Once the goals have been set, treatments are chosen

Unfortunately, many treatments have never been tested

scientifically in ways that answer the questions that are

of interest to clinicians and their patients (e.g.,

probabil-ity of benefit, size of benefit, onset time and duration of

response, frequency of complications of treatment), and

many aspects of treatment are difficult to measure through

scientific experiments Fortunately, drugs and procedures

are increasingly being subjected to clinical trials, and

mea-sures of quality of life are being included in the evaluation

of therapies

The clinical trial is the current standard for

assess-ment of drugs and therapeutic procedures The strongest

clinical trials are randomized, double-blinded controlled

trials The strength of a randomized controlled trial (RCT)

is that the study groups are likely to be similar with

respect to known determinants of outcome, as well as those

determinants that are unknown However, randomization

is often difficult to accomplish in the real world, where

patients are free to join or refuse to join a clinical trial

and where money to support research is limited

Theoreti-cally, in a trial that is double blinded (meaning that neither

the patient nor the researcher knows who is receiving the

experimental treatment), the researchers’ and patients’

as-sessment of outcome is not biased by prior knowledge of

their assignment (e.g., to placebo or to active treatment)

However, studies may not be truly blinded; for example,

in a trial ofβ-blockers against placebo, patients and

clin-icians can measure pulse rates Nonetheless, the clinical

trial is the least-biased method currently available for

re-searchers to test how well drugs and other interventions

work in ideal situations (efficacy) and in the real world

(ef-fectiveness) Table 2.5 lists guidelines that clinicians can

use when assessing the results of a clinical trial As

of Treatment (Clinical Trials)

Was the assignment of patients to treatments really randomized?

Were all clinically relevant outcomes reported?

Were the study patients recognizably similar to my own?

Were both statistical and clinical significance considered?

Is the treatment feasible for patients in my practice?

Was the analysis performed on an intention-to-treat basis?

Were all patients who entered the study accounted for at its

conclusion?

Adapted from Sackett DL, Haynes RB, Guyatt GH, et al Clinical

epidemiology: a basic science for clinical medicine 2nd ed Boston: Little,

Brown, 1991.

trated in the table, there are important questions to ask

of a clinical trial that reports benefits to treated subjects

Were clinically relevant outcomes, such as measures ofpatient health (e.g., morbid events, functional status) re-ported, and not just surrogate end points (e.g., reduction

of blood pressure)? Was all-cause mortality, not just tality caused by the disease in question (e.g., colon can-

mor-cer), reported? In addition to reporting the statistical nificance of findings (the probability that the findings are true), did the study discuss or clarify the clinical significance of the findings (whether the benefits were clinically

sig-meaningful)? As the size of a study increases, there is anincreased likelihood that clinically small or nonmeaning-ful benefits, which are nonetheless statistically significant,will be demonstrated

Moreover, one must pay close attention to the followup

of the subjects enrolled in trials; intention-to-treat

analy-sis is a strategy for analyzing data in which all study ticipants are analyzed in the group to which they wereassigned, regardless of whether they dropped out, werenoncompliant, or crossed over to another treatment ornontreatment group Such an analysis may weaken theability of a study to demonstrate the effect of a treatment,but it prevents selection biases caused by differences inparticipants who drop out from a treatment comparedwith those who remain

par-Researchers often report treatment outcomes in terms

of the relative risk reduction (RRR), which is the difference

in the event rate between control and experimental groups

of patients expressed as a proportion of the event rate in thecontrol group: RRR= (control event rate − experimentalevent rate)÷ control event rate The difference between

the control and experimental event rates is the absolute risk reduction (ARR): ARR= control event rate − experi-mental event rate RRR can alternatively be expressed asthe ARR divided by the control event rate: RRR= ARR ÷control event rate RRR is only meaningful in the context

of absolute risk and can be misleading when applied toindividual patients If someone is at very low risk for anadverse outcome, a treatment with even a high RRR willhave negligible effect on their absolute risk On the otherhand, for someone who is at high risk for an adverse event,even a small RRR can have a significant impact on their ab-solute risk One method of incorporating absolute risk into

an assessment of an intervention’s impact, besides stating

ARR, is to calculate the number needed to treat (NNT) This

refers to the number of persons who need to be treated forone person to benefit and is a more useful measure for aclinician than the RRR The calculation for NNT is simply100%/ARR, with ARR expressed as a percentage, or 1/ARR,with ARR expressed as a fraction (e.g., 0.10 for an ARR of10%)

These concepts can be illustrated using the results oftwo trials of beta-hydroxy-beta-methylglutaryl-coenzyme

A (HMG-CoA) reductase inhibitors (“statins”) for the

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Comparison of Two Trials

Control Treatment

Trial (placebo) (statin) (Control − Treatment) ÷ Control Control − Treatment 100% ÷ ARR

4S (1) 22% 14% (22%− 14%) ÷ 22% = 36% 22%− 14% = 8% 100%÷ 8% = 12 patientsCAPS (2) 2.9% 1.7% (2.9%− 1.7%) ÷ 2.9% = 41% 2.9%− 1.7% = 1.2% 100%÷ 1.2% = 83 patients

ARR, Absolute risk reduction; NNT, number needed to treat; RRR, relative risk reduction.

Data from (1) Scandinavian Simvastatin Survival Study Randomised trial of cholesterol lowering in 4444 patients with

coronary heart disease Lancet 1994;344:1383, and (2) Downs JR, Clearfield M, Weis S, et al Primary prevention of

acute coronary events with lovastatin in men and women with average cholesterol levels: results of AFCAPS/TexCAPS.

Air Force/Texas Coronary Atherosclerosis Prevention Study JAMA 1998;279:1615.

prevention of myocardial infarction The Scandinavian

Simvastatin Survival Study (4S) included subjects with

high cholesterol levels and a history of coronary heart

disease (8) In contrast, the Air Force/Texas Coronary

Atherosclerosis Prevention Study (AFCAPS/TexCAPS) trial

included a lower-risk group of individuals with average

cholesterol levels and no known heart disease (9) Table 2.6

provides the rates of myocardial infarction (fatal and

non-fatal) in each trial and shows how to calculate the RRR,

ARR, and NNT Although treatment with a statin in both

trials yielded similar relative risk reductions (≈40%), the

absolute risk reductions and numbers needed to treat are

quite different This illustrates the importance of

under-standing an individual’s risk when trying to gauge the

impact of a therapeutic intervention; a practitioner (on

average) would need to treat 83 patients with average

cholesterol levels and no history of heart disease with a

statin for 5 years to prevent a myocardial infarction, while

only 12 patients with high cholesterol levels and heart

dis-ease would need to be treated to prevent one event

There are a few caveats about clinical trials Althoughthe RCT is the best study design for assessing the value

of a treatment, one should be cautious about relying on

the results of any single study, even one that was done

well Systematic reviews and meta-analyses, which

com-bine the results a number of studies, are discussed later

in this chapter (see Keeping Up) Sometimes clinical

tri-als have not been performed In this situation, the clinician

may need to rely on cohort, case-control, or cross-sectional

studies These types of studies are more commonly used

to assess risk or harm and are discussed in the next

sec-tion

RISK OR POTENTIAL HARM

Practitioners are frequently called on to make assessments

and judgments regarding risk or potential harm

result-ing from either medical interventions or environmental

exposures Table 2.7 summarizes some of the guidelines forassessing evidence of harm Ideally, these questions would

be answered in a RCT; however, for obvious ethical sons, RCTs are not undertaken with the intent of studying

rea-a hrea-armful exposure Sometimes, rea-a potentirea-ally beneficirea-alintervention is unexpectedly found to be harmful in a clin-ical trial, or there may be both benefits and harms associ-ated with the intervention

More commonly, harm is addressed through

observa-tional studies One kind of observaobserva-tional study is a cohort study, in which exposed and unexposed patients are iden-

tified and monitored for a period of time, and outcomes

in the two groups are compared For example, a cohort

of cigarette smokers and nonsmokers could be monitoredand the incidence of lung cancer in both groups measured

In these studies, the two groups may be different with spect to important determinants of outcome other than

re-the exposure being studied (confounding variables)

Re-searchers often can statistically adjust for these factors,

of Harm

What type of study was reported: a prospective cohort study (with orwithout comparison group); a retrospective case-control study; across-sectional study; a case series; or a case report?

Were comparison groups clearly identified and similar with respect

to potential determinants of outcome, other than the one ofconcern? If not, were differences in potential determinantscontrolled for in the analysis of data?

Were outcomes measured the same way in the groups compared(and was the assessment objective and blinded)?

Was followup sufficiently long and complete?

Was there a temporal relationship between exposure and harm?

Was there a dose–response gradient?

What was the magnitude of the risk, and how precise is thisestimate?

Adapted from Levine M, Walter S, Lee H, et al User’s guides to the medical literature IV: how to use an article about harm JAMA 1994;271:1615.

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but there may be other contributing factors of which they

are unaware

Another method of assessing harm is through

case-control studies In these studies, patients with an outcome

of interest (cases) are identified and compared with others

who are similar in respects other than the outcome

(con-trols) Exposure rates in the case and control groups are

then compared to look at the association between the

expo-sure and the outcome For example, the smoking rate in a

group of patients with lung cancer may be compared with

a group of patients without lung cancer who are otherwise

similar These studies are subject to recall bias: patients

with an illness may be more likely to recall or report an

unusual exposure than those who are not ill In addition,

like cohort studies, they are limited by the possibility of

dif-ferences in unidentified risk factors between the groups

Cohort and case-control studies can also be used to

assess potentially beneficial associations, as was done in

studies that suggested a cardiovascular benefit of hormone

replacement therapy However, this benefit was not

demon-strated when studied in an RCT (10), calling the purported

benefit into question and highlighting the limitations of

observational data

Weaker designs for identifying risk or harm include

cross-sectional studies, case series, and case reports

Cross-sectional studies can establish associations but not causal

links They are strengthened by statistical methods that

control for confounding variables (potential determinants

of harm other than the one of concern) Temporal

relation-ships, however, are usually not established In case reports

or case series, adverse outcomes associated with a

particu-lar exposure are reported in a single patient or group of

pa-tients These reports are useful for identifying potentially

harmful exposures to be studied further, but they are weak

evidence for a causal relationship by themselves However,

if the outcome is very harmful and otherwise rare, this kind

of evidence may be sufficient to take action This might

occur, for example, when severe adverse reactions

associ-ated with a particular medication are reported, especially

if safer alternatives exist A recent example is troglitazone,

which was taken off the market after case reports of severe

hepatotoxicity associated with its use

COST-EFFECTIVENESS

In ambulatory practice, cost considerations arise

fre-quently Cost-effectiveness analyses evaluate health care

outcomes in relation to cost The primary goals are to

de-termine the most efficient use of resources and to minimize

the costs associated with the achievement of health goals

and objectives A common strategy for cost-effectiveness

studies is to compare a novel approach or therapy with

the current practice or standard of care The time frame

of the study should be long enough to allow for costs and

with an Economic Analysis of Clinical Practice

Did the analysis provide a full economic comparison of health carestrategies?

Were the costs and outcomes appropriately measured and valued?

Were the estimates of costs and outcomes related to the baselinerisk in the treatment population?

Was a sensitivity analysis performed that included a range ofestimates for important assumptions? Are the findings consistentacross reasonable ranges of assumptions, or do they change asthe assumptions vary within reasonable ranges?

What were the incremental costs and outcomes of each strategy?

Are treatment benefits worth the harms and costs?

Adapted from Drummond MF, Richardson WS, O’Brien BJ, et al User’s guides to the medical literature XIII: how to use an article on economic analysis of clinical practice JAMA 1997;277:1552.

long-term benefits to be realized The perspective of theanalysis takes into account who benefits from the inter-vention as well as who pays for it (society, the payer, or thepatient) Cost-effectiveness analyses often rely on a num-ber of assumptions, and small variations in one or more

of these parameters can have a significant effect on the

conclusions; a sensitivity analysis can help determine how

sensitive the outcomes are to changes in the parameters

Whether decisions are being made for a population(e.g., frequency of screening colonoscopy, drugs to beadded to a formulary) or for a particular patient (e.g.,choice of antihypertensive medicine), the potential ben-efits should be weighed against the resources used andmoney spent Table 2.8 summarizes some guidelines forassessing evidence in studies performing economic analy-ses

In cost-effectiveness analyses, costs usually are

mea-sured in monetary units (e.g., dollars) and a single

clini-cal outcome is considered (e.g., mortality) In cost-utility analyses, multiple clinical outcomes, including quality

of life, are represented and result in the calculation of

“quality-adjusted life years (QALY).” In both types of yses, alternative diagnostic or therapeutic approaches arestudied with a primary emphasis placed on economic con-siderations

anal-KEEPING UP

One of the major challenges to clinicians is keeping one’spersonal fund of medical knowledge current Studies sug-gest that older practitioners are often “out of date” andtend to provide lower-quality care (11) For primary carepractitioners who are expected to know about a wide ar-ray of clinical topics, keeping up-to-date can be partic-ularly difficult It has been suggested that each practi-tioner should develop a personal mission as to the extent of

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“up-to-datedness” he or she hopes to achieve and maintain

Two questions that may help to better define this territory

are (a) “What information do I need to have in my head to

be satisfied with my knowledge base for the performance

of my job?” and (b) “What information would I be

embar-rassed not to know?” (12)

One author estimated that if clinicians tried to keep upwith the medical literature by reading one article each day,

they would be 55 centuries behind in their reading after

1 year (see Sackett et al., Clinical Epidemiology, at

www.hopkinsbayview.org/PAMreferences) In a seminal

study, experienced clinicians in ambulatory practice said

they had about two clinical questions per week that went

unanswered; however, when shadowed in day-to-day

prac-tice, they were found to actually have about two

unan-swered questions for every three patients seen (13)

More-over, although these clinicians said that their main sources

of information were textbooks and journals, their

behav-ior showed that they got most of their clinical information

from colleagues and drug retailers Fortunately, in

ambula-tory medicine, some high-quality secondary or abstracting

publications exist that produce abstracts and often

pro-vide expert commentary on clinical articles believed to be

of particular importance (approximately 2% to 3% of

arti-cles screened from hundreds of journals) (14) Examples

are the ACP Journal Club and Evidence-Based Medicine.

Scheduling of time to obtain and find relevant readingmaterial is a critical step in keeping up-to-date The ac-

tual reading of the pulled material can occur either in the

scheduled time or when a lull presents itself (e.g., a patient

no-show) Proactive scanning or browsing through a small

number of peer-reviewed journals that regularly yield

arti-cles relevant to one’s clinical practice is an integral part of

keeping up Reactive learning (also called problem-focused

learning) is stimulated by clinical encounters or questions

from patients or medical learners and requires searching

to find the appropriate materials (steps 1 and 2 of the core

EBM skills described at the beginning of this chapter)

Sackett described the “educational prescription” as a means

of phrasing and keeping track of questions as they arise

with the goal and intent of searching for the best available

evidence to answer these queries at some time later A

com-bination of proactive and reactive approaches is thought to

represent the ideal balance for dealing with the evolution

of medical knowledge Several additional ideas have been

suggested by authors who have pondered the challenge of

keeping clinically up-to-date (Table 2.9) (15)

Although original research articles continue to be an cellent source for new information, other types of publica-

ex-tions can also be helpful in the quest to stay current One

common source of medical information is the overview.

The chapters of this book (and other textbooks) are one

ex-ample of an overview; review articles in medical journals

are another These types of overviews are easy to access

(especially if the textbook is at hand) and easy to use; they

Browse at least one general journal regularly

Maintain surveillance on new information

Establish reliable ways of looking up common facts

Identify a set of ways to look up obscure facts

Develop critical appraisal skills

Set aside high-quality time regularly to deal with information needs

Invest time to discover new sources of useful information

From Fletcher RH, Fletcher SW Keeping clinically up-to-date J Gen Intern Med 1997;12:S5.

require little work or effort to obtain needed information

However, they are limited by the biases and limitations ofthe authors and typically do not explain how the informa-tion was gathered or how conclusions were reached

Systematic reviews and meta-analyses published in

peer-reviewed journals with detailed methods describing fically the literature search and the inclusion/exclusioncriteria of the original articles can be invaluable Crit-ical appraisal methods for these two article types havebeen developed and can be applied to evaluate the qual-ity of the work (16); Table 2.10 summarizes these meth-ods Some of the limitations that need to be considered

Article

Are the results of the study valid?

Did the review address an explicitly described, focused clinicalquestion?

Were appropriate criteria (inclusion and exclusion) used forselecting studies for review?

Were search strategies explicitly described, thorough, andappropriate? Is it unlikely that important, relevant studies weremissed?

Was the validity of the included studies appraised and accountedfor?

Were assessments of the studies reproducible?

Were results similar from study to study?

If data from different studies were combined quantitatively, werethe methods explicit and reasonable?

What are the results?

What are the overall results of the review?

How precise are the results?

Are the results presented in a manner that permits comparison andsynthesis of the key features and findings of the studiesreviewed?

Will the results help me in caring for my patients?

Can the results be applied to my patient care?

Were all clinically important outcomes (benefits and harms)considered?

Are the benefits worth the harms and costs?

Adapted from Oxman AD, Cook DJ, Guyatt GH Users’ guides to the medical literature VI: how to use an overview Evidence-Based Medicine Working Group JAMA 1994;272:1367.

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include the heterogeneity of studies (with regard to

pop-ulations studied and outcomes assessed) and the fact that

small studies with negative results are less likely to be

published than those with positive results (publication

bias) Authors often try to correct for these limitations,

but meta-analyses have sometimes yielded results and

con-clusions that were discordant with subsequent large RCTs

(17) Nevertheless, meta-analysis can be a powerful tool

to synthesize the available evidence in an unbiased

fash-ion In addition to those published in medical journals,

the Cochrane Collaboration (and the Cochrane Library—

see www.hopkinsbayview.org/PAMreferences) represents

an international endeavor to develop, maintain, and

dis-seminate systematic reviews on clinical and health-related

topics

Guidelines are systematically developed statements that

offer recommendations to assist with decision making in

specific situations It has been found that clinicians

of-ten do not employ effective interventions (e.g., prescribing

beta-blockers to patients after a myocardial infarction)

Guidelines serve the dual purpose of offering easily

ac-cessible recommendations for practitioners and

publiciz-ing these recommendations to practitioners and the

gen-eral public Guidelines typically are developed by expert

panels They are best when they employ explicit criteria

for gathering the evidence and making recommendations

and acknowledge the level of evidence for each

recom-mendation Guidelines may be biased by the composition

of the expert panel, and sometimes conflicting guidelines

are disseminated by different organizations For example,

the American Urological Association recommends offering

prostate-specific antigen (PSA) determinations to screen

for prostate cancer, whereas the United States Preventive

Services Task Force does not Table 2.11 lists some

sugges-tions for evaluating practice guidelines

Each information source has strengths and weaknesses.

Colleagues may be misinformed Drug retailers have a

product to sell, making them biased Textbooks are often

out of date by the time they are printed Traditional

contin-uing medical education courses provide variable degrees

of evidence-based education and have been shown to have

little effect on practice

How does this guideline compare to other guidelines? Does thegroup issuing this guideline have biases or conflicts of interest?

Have important studies been conducted subsequent to the guidelinethat would alter the recommendations?

Does the burden of the problem addressed warrant implementation

Because “keeping up” with the medical literature resents a colossal challenge, some authors have providedsome direction for how to optimize the chance that one’stime investment will result in a reasonable return (18,19)

rep-They suggest that the usefulness of medical informationfor a given provider is proportional to its relevance, va-

lidity, and accessibility Relevance relates to the frequency with which the provider encounters the topic Validity

refers to the quality of the information and the likelihood

that the information is true Accessibility connotes the

ease with which the information source can be retrieved

These authors recommend that practitioners seek out formation sources that are relevant, valid, and easily ac-cessible

in-Finally, medical librarians can be extraordinary helpful

in keeping clinicians in touch with changes in the cal literature, and they most are happy to meet with clin-icians to make them aware of new resources Befriendingone’s medical librarian is a critical component of a “keep-ing up” strategy and can pay huge dividends in the pursuit

medi-of evidence-based medical practice

∗ Bold numerals denote published controlled clinical

trials, meta-analyses, or consensus-based

recommen-dations.

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Evidence-based medicine: what it is and what it

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Barriers and facilitators to the implementation

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3 Barrows HS, Norman GR, Neufeld VR, et al The

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4 Pewsner D, Battaglia M, Minder C, et al Ruling

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5 Shea JA, Berlin JA, Escarce JJ, et al Revised estimates of diagnostic test sensitivity and specificity in suspected biliary tract disease.

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7 McGee S Simplifying likelihood ratios J Gen Intern Med 2002;17:646.

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9 Downs JR, Clearfield M, Weis S, et al Primary

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10 Hulley S, Grady D, Bush T, et al Randomized

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11 Choudhry NK, Fletcher RH, Soumerai SB.

Systematic review: the relationship between

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