Isoniazid Plus Antiretroviral Therapy to Prevent Tuberculosis in HIV-infected Persons

The purpose of this study is to evaluate whether isoniazid can safely (and further) reduce the risk of tuberculosis in HIV infected people receiving HAART.

The incidence of Tuberculosis (TB) in poor settlements around Cape Town continues to rise despite highly-active-anti-retroviral therapy (HAART) roll-out and DOTS. In Khayelitsha district, where this project will be conducted, TB incidence is about 1600/100000. There is an equally high HIV prevalence, currently 33%. Over 50% of adults presenting with active TB are co-infected with HIV and a third of all patients starting HAART have active TB. Although HAART has been shown to reduce the overall risk of TB by 59-80%, this risk still far exceeds the general risk. In the Khayelitsha HAART cohort, the risk of developing TB whilst on HAART is \~12 per 100 p-y. In the nearby community of Gugulethu, there is a 14% risk of active TB with at least half of the cases occurring within the first 3months on HAART. In a region where RD1-detected prevalence of latent TB infection is at least 80%, there is a real concern that TB will likely undo the benefit of HAART in the long run. Additional measures are therefore required to reduce the risk of TB in those already receiving or starting HAART. Isoniazid preventive therapy (IPT) represents an option but there is insufficient evidence to determine whether IPT can further (and safely) reduce the risk of TB in the HAART era. In a RCT, we propose to evaluate whether IPT can reduce the risk of active TB in patients receiving HAART.

A total minimum sample size of 1204 is required for the study to detect a 35% reduction in the hazard rates for tuberculosis in the intervention group (h1= 0.052) compared to the control group (h0=0.085) at a power of 80% and a Type II error of 0.05. Our maximum targeted sample size when losses to follow-up and subgroup analyses are considered is 1445. Development of TB will be the primary endpoint.

Additional information (on 10 August 2010):

Recruitment and enrolment into the study was completed in October 2009. We have screened over 2000 patients already on ART and those newly starting ART. However, instead of enrolling our desired maximum sample size of 1445, a revised minimum total of 1368 were instead randomized to the study drug. This followed an amendment to the sample size necessitated by new information on the clinical site; primarily higher rates of patients lost to follow-up at the clinical site than previously anticipated. The amendment to our sample size was reported to, and acknowledged by, the Research Ethics Committee of the University of Cape Town. Follow-up of participants will continue until Oct/November 2011.