Abstract:
Background: Globally, it was estimated that there were 10.4 million tuberculosis cases, of
which 1.2 million were Human Immunodeficiency-virus positive people. Although antiretroviral
therapy reduces 67% of tuberculosis acquisition, high tuberculosis incidence commonly
observed immediately after the therapy. Despite Isoniazid preventive therapy provision after
antiretroviral therapy initiation is poorly understood, it is another public health interventions to
reduce tuberculosis burden.
Objective: To determine isoniazid preventive therapy effect on tuberculosis incidence among
HIV infected adult patients on antiretroviral therapy.
Methods: A five year Hospital based retrospective cohort study design was used. Data
extracted from randomly selected 324 IPT users (exposed) and 324 non IPT users (Unexposed)
patients’ registration card. Data entered to Epi-Data 3.1 and analyzed by STATA 14.2. Bivariate
and Multivariate Cox proportional Hazard was used. Variables with p value < 0.2 at bivariate
were candidate for multivariate. Finally, statistically significant variable was declared at p< 0.05
with 95% confidence interval.
Results: The study showed that TB incidence was 2.8 (95% CI: 1.85-4.3) and 15.3(95% CI: 12-
18.9) per 100 person year observation. Median time to develop TB was 8.01 and 5.9 months
among IPT and non-IPT users, respectively. The risk of developing TB was less likely by 78.5%
among IPT users compared to non-IPT users (AHR=0.215, 95%CI: 0.13-0.34). WHO stage 3
(AHR=2.53, 95%CI: 1.58-4.03) and Stage 4 (AHR=4.15, 95%CI: 2.28-7.56) were more likely to
develop TB compared to those had WHO stage I/II. Moreover, suspected but untreated TB at
ART initiation compared to those didn’t suspected (AHR=1.79, 95%CI: 1.12-2.87) and baseline
BMI <18.5Kg/m2 had higher risk of developing TB (AHR=1.54, 95%CI: 1.04-2.30).
Conclusion and Recommendation: There was 2.8 (95% CI: 1.85-4.3) and 15.3(95% CI: 12-
18.9) new TB cases per 100 person year observation among IPT and non-IPT users, respectively.
Not taking IPT, being in advanced WHO clinical stages, suspected TB at ART initiation and
BMI less than 18.5 Kg/m2 were associated risk of developing TB. All TB/HIV program planners
should pay attention on provision of IPT for all HIV infected eligible patients.
