Determinants and Incidence of Tuberculosis among adults living with HIV, who completed Isoniazid Preventive Therapy from 2019 to 2023, Mainland Tanzania

Abstract

ABSTRACT Objective This study aimed to determine TB incidence, median duration of Isoniazid Preventive Therapy protection (PLHIV), and factors associated with TB among adult People living with HIV (≥15 years) on ART who completed IPT Methodology This secondary analysis examined adult PLHIV who completed IPT using data from the CTC2 database (Jan 2019–Dec 2023, mainland Tanzania). Statistical analysis was conducted in STATA 15, with Cox regression used to identify factors associated with tuberculosis diagnosis. Proportional hazard assumptions were tested using Schoenfeld residuals scatter plots. Results A total of 38,407 adults living with HIV (≥15 years) were included in the analysis. The mean age was 36.7 years, with 63.0% female. The median follow-up time was 17.9 months, during which 901 incident TB cases were identified over 682,252.63 person-months, yielding an incidence rate of 1.40 per 1,000 person-months. The median time to TB development was 10.12 months. Female sex (aHR = 1.23; 95% CI: 0.86–1.75; p = 0.025), being unmarried (aHR = 1.20; 95% CI: 0.71–1.51; p = 0.034), and breastfeeding status (aHR = 1.12; 95% CI:1.02–1.56; p = 0.034) had higher risk of TB. Those aged 25–34 years (aHR = 0.55; 95% CI: 0.33–0.89; p = 0.015) and ≥45 years (aHR = 0.56; 95% CI: 0.32–0.95; p = 0.031) had a lower risk of TB. Geographically, those in Eastern (aHR = 0.21; 95% CI: 0.11–0.42; p < 0.001), Western (aHR = 0.37; 95% CI: 0.19–0.73; p = 0.004), and Lake zones (aHR = 0.78; 95% CI: 0.18–0.50; p < 0.001) had lower TB risk compared to the Northern zone. At Health centres (aHR = 0.57; 95% CI: 0.40–0.81; p = 0.002) and hospitals (aHR = 0.20; 95% CI: 0.11–0.39; p = 0.001) had reduced TB risk compared to dispensary Conclusion Among adults living with HIV on ART who completed IPT in mainland Tanzania, the incidence of TB remained low, confirming the protective benefit of IPT in reducing TB occurrence. Evidence shows IPT protection among PLHIV may last only about 10 months rather than the 18 months stated in the Tanzania HIV treatment guidelines, underscoring the need for earlier and intensified TB screening, revision of IPT guidelines, and consideration of alternative TB preventive therapy regimens.