Isoniazid plus antiretroviral therapy to prevent tuberculosis: a randomised double-blind, placebo-controlled trial

Abstract

Background Antiretroviral therapy (ART) reduces the risk of tuberculosis, but the incidence still exceeds that in HIV-uninfected people. Isoniazid preventive therapy (IPT), which decreases the risk of tuberculosis in people not on ART, may offer additional protection. Methods Pragmatic randomized double-blind placebo-controlled trial to evaluate the effect of 12 months IPT among participants established on or newly starting ART, in Khayelitsha, South Africa (NCT00463086, Lancet D-09-02885). Tuberculosis was excluded at screening by sputum culture. Incident tuberculosis was the primary endpoint. Findings 1,329 participants contributed 3,227 person-years (PY) of follow up in the modified intention-to-treat analysis; 662 on IPT and 667 on placebo. There were 95 incident tuberculosis cases: 2.3 (95%CI 1.6-3.1) versus 3.6 (95%CI 2.8-4.7) per 100 PY in the IPT and placebo arms respectively (hazard ratio 0.63, 95%CI 0.41-0.94). Study drug was discontinued due to grade 3 or 4 raised ALT in 19/662 in the IPT and 10/667 in the placebo arm, risk ratio=1.9 (95%CI 0.90-4.09). In secondary analyses, there was no evidence that the effect of IPT was restricted to those who were positive on tuberculin skin test (TST) or interferon gamma release assay (IGRA): adjusted hazard ratio for those with negative tests 0.43 (95%CI 0.21-0.86) and 0.43 (95%CI 0.20-0.96); for positive tests 0.86 (95%CI 0.37-2.00) and 0.55 (95%CI 0.26-1.24) respectively. No all cause mortality benefit of IPT was demonstrated Interpretation IPT reduced the incidence of tuberculosis in HIV-infected individuals on ART. In this high incidence setting, individuals on ART who have TST or IGRA negative results may also benefit from IPT. IPT can easily be implemented in ART clinics.