The diagnostic adaptive behavior scale evaluating its diagnostic sensitivity and specificity

Introduction All current diagnostic and classification systems Diagnostic and Statistical Manual of Mental Disorders, DSM-5; American Association on Intellectual and Developmental Disabil

http://www.researchgate.net/publication/264629826

The Diagnostic Adaptive Behavior Scale: Evaluating its diagnostic sensitivity and specificity

ARTICLE in RESEARCH IN DEVELOPMENTAL DISABILITIES · AUGUST 2014

Impact Factor: 4.41 · DOI: 10.1016/j.ridd.2014.07.032 · Source: PubMed

DOWNLOADS

278

VIEWS

288

9 AUTHORS , INCLUDING:

Giulia Balboni

Università di Pisa

36 PUBLICATIONS 149 CITATIONS

SEE PROFILE

Scott Spreat Woods Services, Inc.

74 PUBLICATIONS 771 CITATIONS

SEE PROFILE

Keith Widaman

University of California, Davis

174 PUBLICATIONS 9,896 CITATIONS

SEE PROFILE

Patricia Navas University of Zaragoza

19 PUBLICATIONS 44 CITATIONS

SEE PROFILE

Available from: Giulia Balboni Retrieved on: 31 July 2015

The Diagnostic Adaptive Behavior Scale: Evaluating its

diagnostic sensitivity and specificity

Giulia Balbonia,* , Marc J Tasse´b, Robert L Schalockc,

Sharon A Borthwick-Duffyd, Scott Spreate, David Thissenf, Keith F Widamang,

Dalun Zhangh, Patricia Navasb

a

University of Pisa, Via Roma, 67, 56126, Pisa, Italy

b

The Ohio State University, 1581 Dodd Dr., Columbus, OH 43210, USA

c

Hastings College, P.O Box 285, Chewalah, WA 99190-0285, USA

d

University of California – Riverside, 20500 Yate Circle, Riverside, CA 92508-3126, USA

e Woodland Center for Challenging Behaviors, 9 Imlaystown-Hightstown Road, Allentown, NJ 08501-2011, USA

f University of North Carolina – Chapel Hill, CB #3270, Chapel Hill, NC 23599-3270, USA

g

University of California – Davis, One Shields Avenue, Davis, CA 95616-8686, USA

h

Texas A&M University, 4225 TAMU, College Station, TX 77843-4225, USA

1 Introduction

All current diagnostic and classification systems (Diagnostic and Statistical Manual of Mental Disorders, DSM-5; American Association on Intellectual and Developmental Disabilities’ [AAIDD] Terminology & Classification Manual; and International Statistical Classification of Diseases and Related Health Problems, ICD-10) have three common criteria to

rule-in or rule-out a diagnosis of Intellectual Disability (ID): (a) significant limitations rule-in rule-intellectual functionrule-ing, (b) significant limitations in adaptive behavior, and (c) an age of onset during the developmental period (American Psychiatric

A R T I C L E I N F O

Article history:

Received 5 June 2014

Accepted 14 July 2014

Available online

Keywords:

Adaptive behavior

Intellectual disability

Sensitivity

Specificity

A B S T R A C T

The Diagnostic Adaptive Behavior Scale (DABS) was constructed with items across three domains – conceptual, social, and practical adaptive skills – and normed on a representative sample of American individuals from 4 to 21 years of age The DABS was developed to focus its assessment around the decision point for determining the presence or absence of significant limitations of adaptive behavior for the diagnosis of Intellectual Disability (ID) The purpose of this study, which was composed of 125 individuals with and 933 without an ID-related diagnosis, was to determine the ability of the DABS to correctly identify the individuals with and without ID (i.e., sensitivity and specificity) The results indicate that the DABS sensitivity coefficients ranged from 81% to 98%, specificity coefficients ranged from 89% to 91%, and that the Area Under the Receiver Operating Characteristic Curve were excellent or good These results indicate that the DABS has very good levels of diagnostic efficiency

ß2014 Published by Elsevier Ltd

* Corresponding author at: Department of Surgery, Medical, Molecular & Critical Area Pathology, University of Pisa, Via Roma, 67, 56126 Pisa, Italy Tel.: +39 050 992370; fax: +39 050 992658.

E-mail address: giulia.balboni@med.unipi.it (G Balboni).

Contents lists available atScienceDirect Research in Developmental Disabilities

http://dx.doi.org/10.1016/j.ridd.2014.07.032

Adaptive behavior has been formally included in defining the condition of ID for at least the past 50 years (seeHeber,

adaptive behavior as originally proposed by Heber (1959) where adaptive behavior was defined as the collection of conceptual, practical, and social adaptive skills Both the AAIDD (Schalock et al., 2010) and the DSM-5 (APA, 2013) define adaptive behavior similarly Moreover, there is agreement in defining significant limitations in adaptive behavior as performance that is approximately two standard deviations below the mean (i.e., represented by a standard score of approximately 70 or less) in at least one of the three adaptive behavior domains of conceptual, social, or practical adaptive skill or in a total score from an adaptive behavior scale (APA, 2013; Schalock et al., 2010)

With the advent of the intelligence tests movement, Intelligence Quotient (IQ) scores quickly became the predominant criterion for diagnosing persons as having ID as well as planning interventions and services for this population, overshadowing consideration of the person’s adaptive behavior skills and deficits Perhaps due to debate over the precise structure of adaptive behavior (Bruininks, McGrew, & Maruyama, 1988; Harrison, 1989; Meyers, Nihira, & Zetlin, 1979;

relevance of the construct of adaptive behavior and the role it should play in a diagnosis of ID has clearly been reaffirmed Despite being an integral part of diagnosing intellectual disability, a relative paucity of research studies have investigated the accuracy with which standardized adaptive behavior measures accurately identify persons with ID as having significant limitations in adaptive behavior A key issue in such studies in identifying those behaviors that best distinguish individuals with ID from those without ID Although more than 200 adaptive behavior measures have previously been identified

developed specifically for the purpose of ruling in/out a diagnosis of ID (Tasse´ et al., 2012) The four instruments normed on representative US samples are: (1) Vineland Adaptive Behavior Scales-2nd edition, VABS-II (Sparrow, Cicchetti, & Balla,

2005); (2) Adaptive Behavior Assessment System-II, ABAS-II (Harrison & Oakland, 2003); (3) Scales of Independent Behavior-Revised, SIB-R (Bruininks, Woodcock, Weatherman, & Hill, 1996); and (4) Adaptive Behavior Scale-School Version, ABS-S:2

When reviewing the psychometric properties of these measures, accuracy to correctly identify persons with ID from individuals without ID is a key aspect The accuracy of differential diagnosis may be evaluated comparing the standard scores

of assessed individuals with and without and ID diagnosis and computing diagnostic efficiency (or validity) statistics (e.g.,

ID) that are correctly identified as having ID by the test (Altman & Bland, 1994), reflecting how good a test is at correctly identifying people who have the condition the test is intended to measure (Loong, 2003) Specificity refers to the ability to correctly reject a diagnosis or identify true negatives, when the person is known not to have the said diagnosis (Altman &

Information regarding the sensitivity and specificity of an adaptive behavior assessment instrument is critical in establishing the valid use of the instrument For example, in the case of the ABS-S: 2, the authors stated simply that ‘‘mean scores for the groups with developmental disabilities are sufficiently below the average scores of the normal group’’

precision of the ABS-S: 2 to accurately measure significant limitations in adaptive behavior and correctly identify someone as having an ID is not known

The SIB-R Comprehensive Manual (Bruininks et al., 1996) provided a more detailed description of sensitivity and specificity In the manual, the authors stated that 76% of the individuals within the standardization sample were correctly classified into their original groups (51% mild ID; 74% moderate ID; and 82% non-ID) From a decision-making perspective, the fact that the lowest degree of accuracy (i.e., 51%) of the SIB-R is for the group with mild ID is not surprising, as this group is the closest to the actual diagnostic cut-off score However, if only about half of persons diagnosed with mild ID have scores in

a range that would support diagnosis, the SIB-R may not be sufficiently sensitive to identify correctly persons with mild forms of ID Furthermore, although the SIB-R covers the age span (from infancy and up), sensitivity and specificity data were not provided for separate age groups

For the VABS-II (Sparrow et al., 2005), the percentages of people correctly classified ranged from 71% to 100% for those aged 6–18 years old (71% mild ID; 87% moderate ID; and 100% severe and profound ID), and from 97% to 100% for individuals aged 19–86 (97% mild ID and 100% for individuals with moderate and with severe and profound ID) Data regarding the sensitivity of the VABS-II were also available by domain (i.e., communication, daily living skills, socialization, and motor skills) However, the proportion of people who were correctly excluded from the diagnosis of ID (i.e., specificity) was not reported

The ABAS-II (Harrison & Oakland, 2003) offers data on both sensitivity and specificity across four infant-preschool samples, five school-age samples, and one adult sample The results for the infant-preschool samples indicate that 58–73% of those with ID (sensitivity), and 0–5% without ID (specificity) scored at least 2 standard deviations below the mean on the General Adaptive Composite (GAC) score, whereas 77–86% children diagnosed with ID and 3–19% of the matched control group scored at least 2 standard deviations below the mean on one or more adaptive domains or the GAC Across the five school-age samples and the adult sample 50–87% of those with ID and 0–17% of the matched control group scored at least 2 standard deviations bellow the mean on the GAC, and 62–100% with ID and 5–19% without ID scored at least 2 standard deviations below the mean on one or more adaptive domains or the GAC

Although the four standardized measures of adaptive behavior briefly reviewed above are appropriate instruments for making a determination of ID, all were generally developed using Classical Test Theory (CTT) models (Tasse´ et al., 2012) In distinction, the Diagnostic Adaptive Behavior Scale (DABS;Tasse´ et al., in preparation) used an Item Response Theory (IRT) model Unlike CTT, IRT models provide guidance in test development and allow scale developers to tailor the efficiency of the instrument for a specific ability level of the trait that is measured For example, given the intended use of an adaptive behavior to provide accurate and precise scores near the cutoff point for diagnosis (i.e., 2 SD below the mean), an IRT approach to scale construction can build up precision at a given point on the standard score scale, which should yield more sensitive measures for diagnostic decisions (Hays, Morales, & Reise, 2000) Moreover, IRT models provide a better estimate of the individual’s true score (Santor & Ramsay, 1998), which is described as a function of the trait (e.g., adaptive behavior) being measured and test item parameters (Thissen, Nelson, Rosa, & McLeod, 2001), such as each item’s level of difficulty and discrimination strength

2 Study purpose

The purpose of this study was to evaluate the DABS with regard to its sensitivity and specificity The DABS is an adaptive behavior assessment instrument that was developed using IRT (Graded Response Model for ordinal polytomous data

diagnosis of ID IRT models were used to estimate the person’s adaptive functioning and item parameters to identify a final set of items that provide the most information around the cut-off point for determining significant limitations in adaptive behavior (i.e., approximately 2 standard deviations below the population mean) from 4 to 21 years old (Tasse´ et al., in

The goals of the present paper include:

(1) comparing the DABS standard score of assessed individuals with and without and ID diagnosis and determining sensitivity and specificity of the DABS to correctly identify persons with an ID diagnosis from individuals who do not have

an ID diagnosis; and

(2) evaluating the sensitivity and specificity across age groups: 4–21 years old

3 Method

3.1 Participants

The participants comprised individuals assessed on the DABS during the standardization phase The sample was composed of 1058 persons, aged between 4 and 21 years old (M = 11.1, SD = 4.9), and 51% were male Individuals in the standardization sample came from 46 American states, with none from Alaska, Arkansas, North Dakota, or West Virginia, and 71.5% were white

As can be seen inTable 1, 125 individuals (12%) had a formal diagnosis of mental retardation/ID or developmental delay and were classified as ‘‘participants with an ID-related diagnosis’’ or the ‘‘ID group.’’ The remaining 933 (88%) were reported

as not having any significant deficits in intellectual functioning and adaptive behavior Of these individuals, 20% had another verified condition that was different from an ID-related diagnosis (e.g., ADHD, learning disability, etc.) These individuals were classified as ‘‘participants without an ID-related diagnosis’’ or the ‘‘non-ID group.’’

The participants were divided into three age groups: 4–8, 9–15, and 16–21 years old (Table 2) In each age group, about 50% were male, and 8%, 9%, and 21%, respectively, had a formal ID-related diagnosis No significant age or gender differences

Table 1 Conditions of the participants.

Prevalence (non-cumulative)

between the ID and non-ID groups were found, with two exceptions: (a) a gender difference (more male participants) in the

ID versus the non-ID participants in the 9–15 year old group,x2

(1)= 6.92, p < 01; and (b) an age difference in the 16–21 year old group, in which participants with ID were slightly older than their peers without ID, t(236)= 1.99, p < 05

3.2 Instrument

The DABS was developed over a 6-year period with the aim of making available an adaptive behavior test that is focused

on providing diagnostic information for ID ID was defined as a condition that is: ‘‘ characterized by significant limitations

in both intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive sills This disability originates before age 18’’ (Schalock et al., 2010, p 1) The DABS reflects both the theoretical and empirical work done over the last two decades, which has supported the 3-factor structure of adaptive behavior as defined inSchalock et al

their everyday lives’’ (Schalock et al., 2010, p 15) (Arias, Verdugo, Navas, & Go´mez, 2013; Navas, Verdugo, Arias, & Go´mez,

The DABS administration is done via a face-to face interview between a professional and a respondent who knows the assessed person very well The individual’s performance of each adaptive skill is assessed according to a four-point rating scale from: 0 (rarely or never does it) to 3 (does it always or almost always independently) and all the items on the DABS must receive a rating

The interviewer of the DABS is described as a professional (e.g., psychologist, teacher, case manager, social worker) or other professional who has completed at least a Bachelor’s degree, has had direct work experience with people with an intellectual or closely related developmental disability, and who has had previous individual assessment experience The DABS should be completed with as many respondents as the interviewer deems necessary to provide the most valid and complete assessment of the assessed person’s adaptive behavior Respondents should inform about individual’s typical performance during daily routines and changing circumstances

As described further inTasse´ et al (submitted for publication), IRT analyses yielded a DABS final version with a total

of 75 items for each of the three age groups (4–8; 9–15; 16–21 years old), consisting of 25 items per domain (conceptual, social, and practical skills) Domain scores for each of the three adaptive skill areas as well as an Overall Adaptive Behavior Standard Score (OABSS) are reported on a standardized scale with a mean of 100 and standard deviation of 15 Therefore, the ‘‘2 SDs below the mean’’ cut-off score for the diagnosis of ID is equal to a standard score of approximately 70 However, the evaluator should also consider the variability of the individual’s observed score caused

by several potential sources of measurement errors The average SEM of the DABS is equal to approximately 3 points for each domain standard score (i.e., conceptual, social, and practical skills) and 2 points for the OABSS Using a 95% confidence interval, the ID diagnosis cut-off represents domain standard score that might go up to 76 (70 + 2 SEM) and 74 (70 + 2 SEM) for the OABSS

3.3 Procedure

Data collection for the DABS standardization was conducted between 2008 and 2011 Participants were recruited nationally through several waves using electronic media, listservs, mailings, and web postings from various professional societies and national disability groups, including: AAIDD, Association of University Centers on Disabilities (AUCD), National Association of School Psychologists (NASP), and APA – Division 33, to name a few

DABS accuracy in the measurement of significant limitations in adaptive behavior was investigated using: (1) comparison

of the standard score of assessed individuals with and without an ID-related diagnosis on each domain (i.e., conceptual, social, and practical skills) and the OABSS; and (2) estimation of sensitivity and specificity in correctly identifying assessed individuals with and without an ID-related diagnosis based on their DABS scores (i.e., a standard score on one of the three domains or the OABSS that was at or below 76 or 74, respectively)

Table 2

Age and gender of participants with and without and ID-related diagnosis within each of the three age groups.

Age groups 4–8 (n = 388)

9–15 (n = 432)

16–21 (n = 238) ID-related

(n = 32)

Non ID (n = 356)

ID-related (n = 42)

Non ID (n = 390)

ID-related (n = 51)

Non ID (n = 187) Age

Gender (%)

3.4 Analyses

Comparisons of standard scores were performed using t-tests When statistically significant differences were found, Cohen’s d was computed (Cohen, 1988), and the effect sizes were interpreted according to the following criteria: negligible (<.20), small (.20–.49), medium (.50–.79), and large (.80) effect size

Test sensitivity was calculated as the proportion of individuals with an ID-related diagnosis who were correctly identified

by the DABS (i.e., who obtained a standard score on one of the three domains that was at or below 76 or an OABSS that was at

or below 74) Test specificity was calculated as the proportion of individuals without an ID-related diagnosis who did not have a domain standard score at or below 76 or an OABSS at or below 74

One can combine the sensitivity and specificity into a single statistic called Overall Correct Classification (OCC) The OCC is defined as the proportion of all individuals with and without an ID-related diagnosis who were correctly identified and detected by the DABS, respectively (e.g.,McFall & Treat, 1999; Streiner, 2003)

If expressed in percentage form, sensitivity, specificity, and OCC are determined to be statistically significant if their CIs do not include the value of 50% (i.e., if they are more accurate than a random classification).Matthey and Petrovski (2002)

suggested that sensitivity coefficients 70% and specificity coefficients 80% are considered appropriate benchmarks to be attained by diagnostic tests Higher values of sensitivity, specificity, and OCC are always desirable

Another way to measure sensitivity and specificity in discriminating participants with and without ID based on their DABS scores was estimated using Receiver Operating Characteristic (ROC) curves analyses The ROC is computed by plotting the true positive rate (sensitivity) against the false positive rate (1 – true negatives or 1 – specificity) for different possible cut points on the DABS (e.g.,Altman & Bland, 1994; McFall & Treat, 1999; Streiner, 2003) The Area Under the Curve (AUC) is equal to the probability of a test giving a correct diagnosis (i.e., correctly identifying individuals with and without ID) In other words, the AUC reflects the probability that a randomly selected person from the ID group will have a standard score below the standard score of a randomly selected person from the non-ID group AUC values range from 0 to 1 and are statistically significant if their CIs do not include the value of 5.Swets (1998)suggested the following parameters when interpreting AUC values: 5–.6 = fail; 6–.7 = poor; 7–.8 = fair; 8–.9 = good; and 9–1.0 = excellent For each age group, comparisons within the AUCs of the standard scores for the DABS Overall Adaptive Behavior and the conceptual, social, and practical domains were confirmed by analyzing the presence or absence of overlaps between the corresponding CIs

4 Results

4.1 Comparisons of DABS standard score obtained by participants with and without an ID-related diagnosis

As shown inTable 3, the mean OABSS for those within the ID group aged 4–21 years old was significantly below (p < 001) the mean OABSS of the assessed individuals within the non-ID group aged 4–21 years old (with effect sizes greater than 2.20, meaning that the difference is larger than two standard deviations) As expected (seeFig 1), all the individuals with an ID-related diagnosis, with the exception of those who were 10 years old, had a mean OABSS below the ID diagnosis cut-off standard score of 74 The mean OABSS was approximately 100 for those without an ID-related diagnosis, regardless of their age range Standard deviations (seeTable 3) were approximately 15 for the non-ID groups (i.e., 4–8; 9–15; 16–21 years old) Consistent with the greater variability in adaptive behavior presented by individuals with ID, standard deviations were larger for individuals within ID-groups (ranging from 17.05 to 19.34) Also, on the conceptual, social and practical skills domains (seeTable 3), participants within the ID group obtained mean standard scores for the conceptual, social and practical skills domains that were significantly lower (p < 001) than the mean standard score obtained by the participants without an ID-related diagnosis (with large effect sizes) at each age level.Fig 2presents the mean standard scores for

Table 3

Comparisons of the standard score obtained by the participants of each of the three age groups with and without and ID-Related diagnosis on the domains and on the Overall Adaptive Behavior scale: standard score Mean (SD), t-test and Cohen’s d values.

Age groups

ID (n = 32) Non-ID

(n = 356)

t value (Cohen’s d)

ID (n = 42)

Non-ID (n = 390)

t value (Cohen’s d)

ID (n = 51) Non-ID

(n = 187)

t value (Cohen’s d) Domains

Conceptual 64.22

(22.39)

100.55 (14.89)

9.00 (2.33) 64.88

(18.69)

99.93 (15.04)

13.99 (2.29) 54.70

(14.44)

99.54 (15.51)

18.56 (2.91)

(13.27)

100.81 (14.87)

10.11 (1.87) 72.10

(16.88)

99.91 (15.09)

11.21 (1.83) 63.73

(15.99)

99.44 (15.27)

14.65 (2.33) Practical 72.72

(19.23)

100.17 (14.55)

7.87 (1.84) 72.16

(20.28)

100.39 (15.37)

10.93 (1.79) 60.88

(16.61)

99.16 (15.45)

15.43 (2.47)

(17.94)

100.60 (14.83)

12.23 (2.26) 65.64

(19.34)

100.03 (15.17)

13.56 (2.22) 53.33

(17.05)

99.30 (15.40)

18.46 (2.97)

participants with and without an ID-related diagnosis This figure shows that, generally, the standard scores for individuals with an ID-related diagnosis fell under the ID cut-off score of 76 The only exceptions noted were for 4, 5, 9, and 10 years old participants for the Social skills domains and for the 4, 10 and 15 years old participants for the Practical skills domain, for which the mean standard score was higher than the cut-off point However, for these age groups the mean OABSS was generally below the ID cut-off point

4.2 Sensitivity and specificity of the DABS

False negatives (i.e., participants with an ID-related diagnosis who obtained DABS standard scores above the ID diagnosis cut-off point) and false positives (i.e., participants without an ID-related diagnosis who obtained DABS standard scores below the ID diagnosis cut-off point), sensitivity, specificity, and OCC are reported inTable 4 The DABS yielded sensitivity coefficients ranging from 81% to 98%, specificity coefficients ranging from 89% to 91%, and OCC coefficients ranging from 89%

to 92% Their CIs did not include the value of 50% (i.e., they were statistically significant) for any age group Sensitivity and specificity were higher than the clinical significance value of 70% (except one value of 68%) and 80%, respectively

Fig 1 DABS Overall Adaptive Behavior standard score of participants with and without an ID-related diagnosis (ID diagnosis cut-off standard score is 74 standard score).

Fig 2 DABS conceptual, social and practical skills standard score of participants with and without an ID-related diagnosis (ID diagnosis cut-off standard

G Balboni et al / Research in Developmental Disabilities 35 (2014) 2884–2893 2889

Moreover, 48% (4–8 years old), 74% (9–15 years old), and 74% (16–21 years old) of the cases that were identified as false positives had some verified condition other than ID (for example, learning disability) that might explain the significant limitations in adaptive behavior

The ROC Curves and AUCs are reported inFigs 3–5, and inTable 5 The CIs of the AUCs for all ages assessed on the DABS were all above 5 Therefore, the DABS is significantly more accurate than a random classification in identifying participants with and without ID Clinical significance was interpreted using the CIs of the AUCs The OABSS for the 4–8 and 16–21 year-old groups and all three domains on the 16–21 year-year-old group had ‘‘excellent’’ discriminant ability in identifying individuals with and without ID (i.e., AUC CI was on the right side of 90) The OABSS for the 9–15 year-old age group and the other remaining domains had discriminant ability that was ‘‘good’’ (i.e., AUC CI was on the right side of 80 and included the value

of 90) Only the practical domain for the 9–15 year-old age group had discriminant ability that was in the ‘‘fair’’ range (i.e., AUC CI was on the right side of 70 and included the value of 80)

The CIs of AUCs for the OABSS and the conceptual, social, and practical domains showed clear overlap across all three DABS forms, indicating that no statistically significant differences were found and that all forms have comparable discriminant ability in correctly differentiating the participants into the ID versus non-ID groups

5 Discussion

The multidimensional framework for understanding adaptive behavior (Schalock et al., 2010) has significant implications for researchers, disability-related government agencies, and services providers Making a diagnosis of ID inevitably is a high stakes decision for various outcomes (e.g., eligibility for accommodations or special education services and supports, waiver services, social security benefits, exemption from the death penalty) (e.g.,Pogge, Stokes, Buccolo, Pappalardo, & Harvey,

2014) Therefore, it is crucial to use valid adaptive behavior scales that enable accurate assessments of significant adaptive skill limitations necessary for an ID diagnosis A standard score of approximately 70 (plus or minus the standard error of measurement) obtained on a comprehensive adaptive behavior test is the cut-score often used in defining significant deficits

in adaptive behavior and a critical element in making a determination of ID (APA, 2013; Schalock et al., 2010) The four other, well-accepted standardized adaptive behavior tests used in making a diagnosis of ID (Vineland Adaptive Behavior Scale-II, Adaptive Behavior Assessment System-II, Scales of Independent Behavior-Revised, Adaptive Behavior Scale: School) were developed to provide adaptive behavior information for both (1) the diagnosis of ID, and (2) planning intervention (Tasse´

Table 4

False negative and positive, sensitivity, specificity and OCC (CI) of the DABS for the three age groups(%).

Note CI, 95% confidence interval; OCC, overall correct classification.

.0 1 2 3 4 5 6 7 8 9 1.0

1 - Specificity

Conceptual Social Practical Total AB

at the cut-score of approximately 2 standard deviations below the population mean for the purpose of ruling-in or ruling-out

a diagnosis of ID

The aim of this paper was to analyze the accuracy of the DABS in providing critical adaptive behavior information for the purpose of ruling-in or out a diagnosis of ID in individuals aged 4–21 years old Hence, we used two different methods to accomplish this goal: (1) comparing group means on the standard scores; and (2) estimating the sensitivity (i.e., the discriminant ability in correctly identify the individuals with an ID-related diagnosis) and specificity (i.e., the discriminant ability in correctly identify the individuals without an ID-related diagnosis) of the DABS Sensitivity and specificity were estimated first by computing the percentage of participants with and without ID who had DABS scores that were below or above the mean, respectively The sensitivity and specificity were also estimated using ROC analyses, which yield AUC values which indicate the probability that a randomly selected person from the ID group will have a DABS standard score below the standard score of a randomly selected person from the non-ID group

Based on the results obtained, the DABS has good to excellent efficiency in correctly identifying whether individuals aged 4–21 years old do or do not have a diagnosis of ID Of the four commonly accepted, well-standardized adaptive behavior scales used in making a diagnosis of ID, the accuracy in identifying individual with ID was investigated estimating only sensitivity and specificity When evaluating the accuracy of the DABS, we extended the sensitivity-specificity analyses with ROC analyses Our analyses showed that the DABS correctly identified 81–98% of individuals with ID and 89–91% of

.0 1 2 3 4 5 6 7 8 9 1.0

1 - Specificity

Conceptual Social Practical Total AB

Fig 4 Receiver operating characteristics (ROC) curves of DABS in 9–15 years old group.

.0 1 2 3 4 5 6 7 8 9 1.0

1 - Specificity

Conceptual Social Praccal Total AB

G Balboni et al / Research in Developmental Disabilities 35 (2014) 2884–2893 2891

individuals without ID These coefficients are comparable to or exceed those reported with the other standardized adaptive behavior scales for individuals 4–21 years old

The ABAS-II (Harrison & Oakland, 2003) reported that school age subjects with an ID scored significantly lower (range 56– 73) on the ABAS-II GAC than their typical peers (range 93–101) Harrison and Oakland also reported 50%-87% of the subjects assessed on the ABAS-II who had a diagnosis of ID scored at least 2 standard deviations below the mean on the GAC They did not, however, report the sensitivity of the ABAS-II in identifying subjects with ID using 2 standard deviations below the mean

on at least 1 of the 3 domains independently from the GAC The ABS:School-2 (Lambert, Nihira, & Leland, 1993) did not report data on its accuracy rate in correctly distinguishing students known to have an ID diagnosis from those who do not The DABS does not attempt to provide an exhaustive assessment of an individual’s strengths and limitations in adaptive functioning, and therefore should not be used for the purposes of programming or identifying areas of intervention or needed supports Other instruments are available and may be used for planning intervention and measure adaptive behavior profile (e.g.,Brian, Belva, & Matson, 2013; Matson, Dempsey, & Fodstad, 2009; Matson, Rivet, Fodstad, Dempsey, & Boisjoli, 2009;

maximally differentiate between individuals 4 and 21 years old with and without ID, and provides reliable behavioral information around the cutoff point for determining significant limitations in adaptive behavior Dedicated efforts were made during scale development to obtain an instrument focused on identifying significant limitations in adaptive behavior

to aid in the diagnosis of ID Based on the results of this investigation, the DABS performs as well as, and at times better than, the other four existing adaptive behavior scales used in the diagnosis of ID (i.e., Vineland Adaptive Behavior Scale-II, Adaptive Behavior Assessment System-II, Scales of Independent Behavior-Revised, Adaptive Behavior Scale: School), while having substantially fewer items and reduced administration time

Acknowledgment

The investigation was partially supported by the Research Grant: ‘‘Development of a Diagnostic Assessment Instrument

to Assess Adaptive Behavior.’’ funded by the American Association on Intellectual and Developmental Disabilities (Marc J Tasse´, Principal Investigator)

References

Altman, D G., & Bland, J M (1994) Diagnostic tests 2: Predictive values British Medical Journal, 309(6947), 102.

American Psychiatric Association (2013) Diagnostic and statistical manual of mental disorders (5th ed.) Arlington, VA: American Psychiatric Publishing.

Arias, B., Verdugo, M A., Navas, P., & Go´mez, L E (2013) Factor structure of the construct of adaptive behavior in children with and without intellectual disability International Journal of Clinical and Health Psychology, 13, 155–166.

Brian, C., Belva, B C., & Matson, J L (2013) An examination of specific daily living skills deficits in adults with profound intellectual disabilities Research in Developmental Disabilities, 34, 596–604.

Bruininks, R H., McGrew, K., & Maruyama, G (1988) Structure of adaptive behavior in samples with and without mental retardation American Journal on Mental Retardation, 93, 265–272.

Bruininks, R H., Woodcock, R., Weatherman, R., & Hill, B K (1996) Scales of independent behaviour-revised Park Allen, TX: DLM Teaching Resources.

Cohen, J (1988) Statistical power analysis for the behavioral sciences (2nd ed.) Hillsdale, NJ: LEA.

Greenspan, S., & Grandfield, J M (1992) Reconsidering the construct of mental retardation: Implications of a model social competence American Journal of Mental Retardation, 96, 442–453.

Harrison, P L (1989) Adaptive behavior: Research to practice Journal of School Psychology, 23, 301–313.

Harrison, P L., & Oakland, T (2003) Adaptive Behavior Assessment System (2nd ed.) San Antonio, TX: Harcourt Assessment.

Hays, R D., Morales, L S., & Reise, S P (2000) Item response theory and health outcomes measurement in the 21st century Medical Care, 38(Suppl 9), 28.

Heber, R (1959) A manual on terminology and classification in mental retardation American Journal on Mental Deficiency Monographs, 64(2), 1–111.

Heber, R (1961) A manual on terminology and classification on mental Washington, DC: American Association on Mental Deficiency.

Lambert, N., Nihira, K., & Leland, H (1993) AAMR adaptive behavior scales – School (ABS-S:2): Examiner’s manual (2nd ed.) Austin, TX: Pro-Ed.

Loong, T W (2003) Understanding sensitivity and specificity with the right side of the brain British Medical Journal, 327(7417), 716.

Luckasson, R., Borthwick-Duffy, S., Buntinx, W H., Coulter, D L., Craig, E M P., Reeve, A., et al (2002) Mental retardation: Definition, classification, and systems of supports (10th ed.) Washington, DC: American Association on Mental Retardation.

Matson, J L., Dempsey, T., & Fodstad, J C (2009) The effect of Autism Spectrum Disorders on adaptive independent living skills in adults with severe intellectual

Table 5

Area under the curve (AUC) (CI) of the DABS in the three age groups.

Age groups

Domains

Note CI, 95% confidence interval; OABSS, Overall Adaptive Behavior SS.