Effect of Isoniazid Prophylaxis Therapy on the Prevention of Tuberculosis Incidence and Associated Factors Among HIV Infected Individuals in Northwest Ethiopia: Retrospective Cohort Study

BACKGROUND: Treating latent tuberculosis (TB) infection with Isoniazid (INH) among human immune virus (HIV) infected patients reduces active TB occurrence and death by 62% and 26%, respectively. Even though other studies show aforementioned evidence, TB incidence and its associated factors among HIV-infected individuals who were on INH and never on INH is not well studied in northwest Ethiopia. Therefore, this study tried to assess the effect of INH prophylaxis in TB prevention and associated factors among HIV-infected individuals. METHODS: Data were extracted from charts of HIV-infected clients who completed INH (193) and were never on INH (198) after a simple random sampling selection was done among newly diagnosed patients on follow-up from 2008 to 2015. After data were collected, it was entered into Epi info version 7 and exported to SPSS version 22 for analysis. Cox regression model was fitted and the hazard ratio was reported. RESULTS: In this study, the overall TB incidence rate among HIV patients was 3.5/100 person-years (PY) [95% CI: 2.55, 4.82]. But it was 7.1/100 PY among patients who were never on INH and 0.35/100 PY among patients who completed INH. INH completed [adjusted hazard ratio (AHR) = 0.08, 95% CI: 0.02–0.37], on anti-retroviral therapy (ART) [AHR = 0.02, 95% CI: 0.01–0.04], baseline World Health Organization (WHO) stage I & II [AHR =0.22, 95% CI: 0.08–0.62] and baseline CD4 ≤ 350 [AHR=3.76, 95% CI: 1.39–10.18] were significantly associated with TB incidence. CONCLUSION: Putting patients on INH for 6 months and ART were protective factors against TB. Therefore, health institutions are recommended to provide INH after ruling out active TB and contraindications for HIV-infected individuals.