Short and Long-Term Incidence of Tuberculosis and CD4-Cell Count Dynamic on HAART in Senegal

Estimate tuberculosis (TB) incidence among patients receiving HAART. Compare the dynamic of the CD4-cell count and viral load before notification of the TB with the dynamic among patients remaining free of TB.

Prospective cohort with ascertainment of TB cases from medical records.

The first 404 adults HIV-1 infected patients enrolled in the Senegalese antiretroviral drug access initiative were eligible. CD4-cell and viral load were assessed at baseline and every 6 months. Patients receiving an antituberculosis treatment at HAART initiation were excluded from analysis. Any TB case notified after the first month of HAART was considered as an incident case. Follow-up was censored at death or at the last visit before March 31, 2008. CD4-cell trajectories until TB notification were compared to non-TB developers within two distinct periods: from HAART initiation to 24 months and after.

Over 404 eligible patients, 352 were included in this analysis. Median follow-up reached 73 months and 1821 person-years were accrued. Half of the 42 incident cases were notified before month 19 of HAART yielding to an overall incident rate of 2.3/100 PY [1.7-3.1]. Annual incidence decreased with duration of HAART (trend in incidence: RR=0.26, p<10(-4)). During the first period, CD4-cell count dynamic of most TB patients was identical to the dynamic among patients remaining free of TB. Most cases of the second period occurred in a context of an immunological failure.

This study provides an estimate of TB incidence among patients on HAART in Senegal and supports two underlying mechanisms.