Incident pulmonary tuberculosis on antiretroviral therapy: seven years of experience at the Themba Lethu Clinic in Johannesburg, South Africa

Abstract

Background: South Africa continues to have the largest HIV treatment program in the w orld alongside one of the w orld’s largest tuberculosis (TB) epidemics. While antiretroviral therapy (ART) reduces the risk of acquiring TB for HIV-infected patients, rates of TB for those on ART remain high. After seven years of delivering HIV treatment, w e describe rates and predictors of incident TB over time in patients initiating ART at a large HIV clinic in South Africa. Methods: We compared rates/100 person-years of incident pulmonary TB at Themba Lethu Clinic. Rates were compared over 6 yearly cohorts since April 2004. Person-time accrued from ART initiation until the earliest of death, loss to follow -up, transfer, incident TB or dataset closure (August 2011). Results: 13,228 ART patients (63.4% female) w ere follow ed for 35,567 person-years. Patients initiated ART at a median (IQR) age of 35.9 (30.9-42.4) and a median (IQR) CD4 count of 92 cells/mm3 (35-161). 699 (5.3%) patients developed incident pulmonary TB in a median (IQR) of 4.9 (1.6-15.0) months. The one-year TB incidence rate on ART fell somew hat from 2.25/100 person-years (95%CI:1.94-2.62) for those initiating ART in 2004/5 to 1.97/100 person-years (95%CI:1.56-2.49) in 2009/10 alongside small increases in median starting CD4 count (82 in 2004/5,114 in 2009/10) and rates of INH prophylaxis (4.9 vs 6.4%) and stable TB prevalence (13.7 vs 14.0%). Among 1,795 patients initiating ART in 2004/5, over 7 years of treatment, 9.5% (n=170) developed incident TB. Incident TB w as strongly predicted by CD4 count at ART initiation with highest TB rates among those w ith the low est CD4 count (< 50 vs ≥350 cells/mm3 HR:2.42;95%CI:1.00-5.86). Conclusions: As experience w ith ART continues, reduction in incident TB on ART is being seen. Future efforts to monitor changes in TB incidence w ith increasing CD4 count initiation criteria are critical to monitoring ART programmes.

Conference: AIDS 2012, Washington DC, USA