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JOURNAL OF SCIENCE, Hue University, N 0 61, 2010 PREVALENCE OF HIV INFECTION AND RISK FACTORS OF TUBERCULIN INFECTION AMONG HOUSEHOLD CONTACTS IN AN HIV EPIDEMIC AREA: CHIANG RAI PROV

JOURNAL OF SCIENCE, Hue University, N 0 61, 2010

PREVALENCE OF HIV INFECTION AND RISK FACTORS OF TUBERCULIN

INFECTION AMONG HOUSEHOLD CONTACTS

IN AN HIV EPIDEMIC AREA: CHIANG RAI PROVINCE, THAILAND

Pornnapa Suggaravetsiri Khon Kaen University, Thailand

Juthatip Putthasorn Chiang Rai Prachanukraow Hospital, Chiang Rai Province, Thailand

SUMMARY

During the course of the HIV epidemic in Chiang Rai Province in Northern Thailand, incidence of tuberculosis also sharply increased Up to the year 2002, there were no specific interventions for the prevention and control of TB infection among the household contacts of an infected person The study aimed to identify prevalence of HIV infection and risk factors of tuberculosis infection among household contacts Methodology: A cross-sectional analytic study was conducted among household contacts of TB cases between January 2001 and January 2002

We collected data using structured interviews, physical examinations, tuberculin skin test (TST), mumps skin test and pre-test and post-test counseling for HIV testing Results: The prevalence of positive tuberculin skin test among 1,211 household contacts was 57.55% and the HIV positive rate among household contacts was 7.74% (72 out of 930 contacts who did agree to HIV testing) Based on the variables entered into the model, gender, age, HIV status, caregivers of

TB patients and living in the same room as the infected patient were significantly related to TB infection However, the presence of a BCG scar was not significantly associated with TB infection Conclusion: TB screening every 6 months should be provided to household members and children who had contacts with HIV positive individuals and the introduction of anti TB prophylaxis should be provided to HIV infected persons

Keywords: Tuberculosis, Households, Risk factors, HIV, Thailand

1 Introduction

Tuberculosis (TB) and Human immune deficiency virus (HIV) are currently the major leading causes of death worldwide among infectious diseases It is estimated that

TB kills more than two million people each year This problem is further aggravated by the alarming spread of HIV and the emergence of drug resistance According to WHO estimates there were 8.8 million new case of TB in 2003 (140/100,000) of which 3.9 million (62/100,000) were positives smear and 674,000 (11/100,000) were infected with

HIV Annually 5% to 15% of HIV- positive individuals develop TB and at least one-third of the world population, that is about 1.9 billion people are infected with TB Within Chiang Rai province in Northern Thailand, 1990-1998 data revealed that the proportions of TB cases attributable to HIV was 72% among males- and 66% among female patients The TB notifications increased from 40/100,000 population in 1990 to 144/ 100,000 population in 2002, which amounted to a three- fold increase in TB This was mostly attributable to HIV Obviously the problem of TB/HIV is an issue of critical importance, and challenging for investigation and control Several studies were conducted to explored risk factors among TB patients, household members, and health care workers However, most of them investigated the risk factors relating to the development of TB rather than its source of infection This study aimed to identify the risk factors of TB infection among household contacts in a HIV epidemic area, Chiang Rai province, Thailand

2 Methodology

A cross- sectional study was carried out between January 2001 and January 2002 Three hospitals located in the epidemic area of Chiang Rai Province, Chiangrai Prachanukroa, Phan and MaeJan, were the study sites Tuberculosis index cases (the first suspected case in each household) were diagnosed by chest radiography (CXR) and tested for acid-fast bacilli (AFB) in sputum TB index cases and the household of each

TB index case were visited by a researcher assistant Household contacts were defined

as members of an extended family of the index case who lived in the same house as the

TB index case Specific information about TB infection from the household contacts was collected by their response to a list of typical clinical symptoms of TB Physical examination, mumps skin test and a tuberculin skin test (TST) were performed at the hospital or at home by well trained nurses Indurative diameters of mumps skin test and the TST were measured within 48 to 72 hours An indurative diameter of ≥ 10 mm of TST was considered to be a positive test (TB infection) Double data entry by using the

data file then was transferred to STATA 7.0 (Texas, USA) for statistical analysis to calculate the proportion of infection among household contacts and examine the effects

of different factors related to the TB infection Multiple Logistic regressions were carried out by the backward elimination method The study was approved by the Ethics Committee of the Public Health Ministry of Thailand

3 Results

From the 526 TB index cases, 221 (42.01%) were TB/HIV- positive and 305 (57.98%) were TB/HIV- negative Among 1,300 household contacts were identified, 1,248 household contacts consented to participant in the study Of these 1,240 (99.36%

of 1,248) agreed for TST and 930 (74.52% of 1,248) consented for HIV testing Twenty-nine persons were excluded because of an allergy to TST The remaining 1,211

study participants were included in the analyses The sex ratio between males and females was almost one to one There were 690 (56.98% of 1,211) with tuberculosis infection Of those 366 (30.22%) were children younger than 14 years with TB infection

There were 930 HIV testing results among household contacts, of which 72 (7.74% of 930) were HIV positive and 685 (56.56 %) had a BCG scar Using a univariate analysis, the risk of being TST- positive was found to be higher among household contacts of HIV negative- than HIV positive index cases The risk of household contacts of developing a positive TST response was associated with the TB index cases and elaborates demographic variables A low educational status increased the risk of TB infection Household members being involved in agricultural and trade activities had higher risks of acquiring TB compared to government officers To be a student was a protective factor of having the infection Married and divorced family members were more at risk of infection than those who were never married Among the family members, spouses had a higher risk of having the infection than other family members of the index cases (Table 1)

Table 1 Rate and odds ratio of tuberculin skin test (TST) positive and characteristics of

household contacts

Characteristic Number and Prevalence

(%) of TST-positive

Crude odds ratio 95% CI

p-value

Sex

Age (years)

Race / Ethnicity

Education

More than high

Occupational

Marital status

Relationship to Index case

Alcohol drinking and smoking were associated with a risk of having infection than non- drinkers and non-smoker The presence of a BCG scar was a protective factor Variables that had a close contact with the index case, such as giving care to them, sleeping in the same bedroom and sleeping in the same bed as the index case, were associated with an increased risk of being infected with TB (Table 2)

Table 2 Univariate analysis of risk factors associated with tuberculosis infectious among

household contacts (1)

negative OR 95 % CI p-value

Alcohol drinking

Cigarette smoking

BCG scar present

HIV status

Care giver to the TB patient

Sleeping in the same bedroom as the

TB patient

Sleeping in the same bed as the TB patient

Open the window

OR = 1.00 is the reference group for each category

A multivariate model was fitted to assess the potential confounding factors and other factors, age and sex, BCG scar present, HIV status of contact, care giver of the TB patient, and sleeping in the same bedroom as the TB patient A potential confounder was only the age group; the multivariate analysis was done to test the magnitude of the

single factor to develop TB infection If this was true then the R2 value would be additional valuable information as it would show the magnitude of how much a given variable determined the variation of the dependent variable or the infection with TB among the household contacts The factors significantly related to being TST positive were being male, older age, and being in close contact to the TB index cases The presence of a BCG scar was not a risk factor for TB infections among household contacts (Table 3)

4 Discussion

This study found that more than 50% of the household contacts of people with

TB and HIV were infected with TB This was lower than studies conducted in Sub-Saharan Africa but higher than studies conducted in other regions The differences between this study and those undertaken in other areas could be due to the use of different methods for identification of cases and family relationships It was not known whether poverty could lead to poor nutrition and low immunity of people when they led

to varying degree of risk of having the TB infection One unexpected result was that those household contacts to an index case who were HIV negative had a higher risk of having TB compared to household contacts with an index case who was HIV positive The reason for this probably was that household contacts knew the HIV positive status

of the index case and had prevention in close contact with the HIV infected person Household contacts with HIV negative index cases might not take that precaution The level of TST indurations of a person with previous BCG immunization ranged from 5.0

mm to 11.3 mm even without natural infection Another possible explanation to the contradictory finding was that a high degree of illness in HIV-infected patients could

result in weaken and perhaps less effective dissemination of M tuberculosis the

patients’ environment In addition, HIV-infected persons probably had a compromised ability to react to tuberculin skin testing, because HIV infection is associated with an elevated risk of skin test allergy

Table 3 Risk factors associated with tuberculosis infection among household contacts of TB

index cases (Multivariate analysis)

Sex

Age (years)

BCG scar present

HIV status

Care giver to the TB patient

Sleeping in the same bedroom as the TB patient

age, BCG scar present, HIV status, care giver to the TB patient, and Sleeping in the same bedroom as the TB patient similar to other studies, the risk of having positive TST was related being male and older age group Males might be less careful and less aware

of the danger in acquiring TB The decreasing immune stimulation probably was related

to older age and a longer term exposure to TB might contribute an increasing risk among older age groups Furthermore, it was found that hill tribe people had a higher

risk to be infected with M tuberculosis then other Thai citizen However the difference

between both groups was not significance Type I error could occur as these were only

85 hill tribe persons included in this study Other factors such as malnutrition, low income, poor access to health care, crowding, and poor hygiene were not explored in this study and required further investigation Another factor was immune status, which was found to be lower among hill tribe people as discussed by Wanda Walton and Patricia Simone The presence of a BCG scar was not a risk factor for TB infection This was similar to what was found in West Africa and might be explained by some protective mechanism of being exposed to the causative agent of TB These also require

further investigation

5 Conclusion

The presence of a positive TST result was consistently higher over all ages in individuals with a BCG scar BCG vaccination was reported to induce cross-reactivity with tuberculin PPD (Purified protein derivative), but the degree of tuberculin sensitivity is highly variable, depending on the vaccine strain used, the dosage, the method of administration, and other factors known to influence the reaction to TST Currently, BCG is given immediately to all babies born in Thailand The coverage is more than 95% nationwide BCG scars consistently had no relationship with TB infection status Therefore, the presence of a BCG scar should not be a factor in the decision-making to treat latent TB infection among children and HIV-infected persons,

as BCG did not appear to prevent the activation of a latent TB infection induced by HIV-related immunodeficiency

Household contacts that had been in close contact with the index case included family members, coworker or friends, and customers as found in other studies In this investigation occupational and marital status was an independent risk factor to TB infection and also family relation, such as being husband or wife, had an impact on the

TB infections of the contacts

Table 4 A Multiple logistic regression analysis of risk factors associated with tuberculosis

infection among household contacts of TB index cases

Sex

Age (years)

BCG scar present

HIV status

Care giver to the TB patient

Sleeping in the same bedroom as the TB patient

age, BCG scar present, HIV status, Care giver to the TB patient, and Sleeping in the same bedroom as the TB patient

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