Effectiveness of isoniazid preventive therapy on incidence of tuberculosis among HIV-infected adults in programme setting

Background & objectives: As India and other developing countries are scaling up isoniazid preventive therapy (IPT) for people living with HIV (PLHIV) in their national programmes, we studied the feasibility and performance of IPT in terms of treatment adherence, outcome and post-treatment effect when given under programmatic settings. Methods: A multicentre, prospective pilot study was initiated among adults living with HIV on isoniazid 300 mg with pyridoxine 50 mg after ruling out active tuberculosis (TB). Symptom review and counselling were done monthly during IPT and for six-month post-IPT. The TB incidence rate was calculated and risk factors were identified. Results: Among 4528 adults living with HIV who initiated IPT, 4015 (89%) successfully completed IPT. IPT was terminated in 121 adults (3%) due to grade 2 or above adverse events. Twenty five PLHIVs developed TB while on IPT. The incidence of TB while on IPT was 1.17/100 person-years (p-y) [95% confidence interval (CI) 0.8-1.73] as compared to TB incidence of 2.42/100 p-y (95% CI 1.90-3.10) during the pre-IPT period at these centres (P=0.017). The incidence of TB post-IPT was 0.64/100 p-y (95% CI 0.04-1.12). No single factor was significantly associated with the development of TB. Interpretation & conclusions: Under programmatic settings, completion of IPT treatment was high, adverse events minimal with good post-treatment protection. After ruling out TB, IPT should be offered to all PLHIVs, irrespective of their antiretroviral therapy (ART) status. Scaling-up of IPT services including active case finding, periodic counselling on adherence and re-training of ART staff should be prioritized to reduce the TB burden in this community.