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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 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

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
software of Epi-info Version 6.02 (Atlanta, USA) was done to validate the data. 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 1,211 405
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

40-49 103/148 (69.59) 5.01 3.21-7.80 <0.01
50-59 82/124 (66.13) 4.27 2.69-6.77 <0.01
≥ 60 93/194 (47.94) 2.01 1.36-2.98 <0.01
Race / Ethnicity
Thai 639/1126 (56.75) 1.00
Hill tribe 51/ 85 (60.00) 1.14 0.73-1.79 0.56 406
Education
More than high
school
126/196 (64.29) 1.00
No education 209/431 (48.49) 0.52 0.37-0.74 <0.01
Elementary 355/584 (60.79) 0.86 0.62-1.21 0.38
Occupational
Government official 138/253 (54.55) 1.00
Agriculture & Trade 219/318 (68.87) 1.84 1.31-2.60 <0.01
Labour 175/251 (69.27) 1.92 1.33-2.77 <0.01
Student 158/389 (40.62) 0.57 0.41-0.78 <0.01
Marital status
Single 244/508 (48.03) 1.00
Married 358/558 (64.16) 1.94 1.52-2.48 <0.01
Divorced 88/145 (60.69) 1.67 1.15-2.43 <0.01
Relationship to Index case
Relative 179/366 (48.91) 1.00
Spouse 203/282 (71.99) 2.68 1.93-3.74 <0.01
Children 121/238 (50.84) 1.08 0.78-1.50 0.64
Parent 187/325 (57.54) 1.42 1.05-1.91 0.02
Alcohol drinking and smoking were associated with a risk of having infection

Sleeping in the same bedroom as the
TB patient

No 379 362 1.00
Yes 311 159 1.87 1.47-2.37 <0.01
Sleeping in the same bed as the TB patient
No 448 395 1.00
Yes 242 126 1.69 1.31-2.18 <0.01
Open the window
Everyday 479 371 1.00
Seldom 75 62 0.94 0.65-1.35 0.73
Never 136 88 1.20 0.89-1.62 0.24
Note:
(1)
Total may not be equal to 1,211 due to missing data.
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 408
single factor to develop TB infection. If this was true then the R
2
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

Female 0.45 0.33-0.61 <0.01
Age (years)
<10 1.00
10-19 3.70 1.89-7.25 <0.01 409
20-29 6.45 3.21-12.96 <0.01
30-39 5.34 2.70-10.57 <0.01
40-49 5.55 2.79-11.05 <0.01
50-59 6.26 2.99-12.87 <0.01
≥ 60 2.56 1.29-5.08 <0.01
BCG scar present
Positive 1.00
Negative 0.74 0.53-1.04 0.08
HIV status
Positive 1.00
Negative 3.15 1.57-6.33 <0.01
Care giver to the TB patient
No 1.00
Yes 2.04 1.48-2.81 <0.01
Sleeping in the same bedroom as the TB patient
No 1.00
Yes 1.99 1.44-2.74 <0.01
Note:
(2)
Variables entered in the Multiple Logistic Regression Analysis were sex,
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

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
Variable Adjust OR
(2)
95 % CI p-value
Sex
Male 1.00
Female 0.45 0.33-0.61 <0.01
Age (years)
<10 1.00
10-19 3.70 1.89-7.25 <0.01
20-29 6.45 3.21-12.96 <0.01
30-39 5.34 2.70-10.57 <0.01
40-49 5.55 2.79-11.05 <0.01
50-59 6.26 2.99-12.87 <0.01
≥ 60 2.56 1.29-5.08 <0.01
BCG scar present 411
Positive 1.00
Negative 0.74 0.53-1.04 0.08
HIV status
Positive 1.00
Negative 3.15 1.57-6.33 <0.01
Care giver to the TB patient
No 1.00

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