To evaluate the short- and long-term effects of highly active antiretroviral therapy (HAART) on tuberculosis (TB) risk, compared to risk without HAART in a low TB incidence setting.
An observational cohort study among HIV-infected persons in care at the Comprehensive Care Center (Nashville, TN) between January 1998 and December 2008.
A marginal structural model was used to estimate the effect of HAART on short- (≤180 days) and long-term (>180 days) TB risk, with CD4+ lymphocyte count incorporated as a time-updated covariate.
Of 4,534 HIV-infected patients, 34 developed TB (165/100,000 p-y; 20,581 person-years [p-y] of follow-up). Seventeen cases occurred among persons not on HAART or >30 days after HAART discontinuation (212/100,000 p-y; 8,019 p-y of follow-up). Seventeen occurred among persons on HAART (135/100,000 p-y; 12,562 p-y of follow-up); ten in the first 180 days (402/100,000 p-y; 2,489 p-y of follow-up) and 7 after more than 180 days (69/100,000 p-y; 10,073 p-y of follow-up). After adjusting for the most recent CD4+ lymphocyte count, the risk of TB in the first 180 days of HAART exposure relative to no HAART was 0.68 (0.14–3.22, p=0.63).
In this low TB incidence setting, the TB rate in the first 180 days of HAART was almost twice as high as persons not on HAART. However, after adjusting for most recent CD4+ count there was no significant difference in TB risk between these two groups. This suggests that low recent CD4+ lymphocyte count influences TB risk during the first 180 days of HAART.