Low CD4+ T-cell count and high HIV viral load precede the development of tuberculosis disease in a cohort of HIV-positive Ethiopians

SETTING: Prospective cohort study, Ethiopia. OBJECTIVE: To study changes in biological markers of HIV infection progression before and after development of TB disease. DESIGN: A longitudinal study of 804 adult factory workers (95 HIV-positive, 709 HIV-negative), who were followed every 6 months for a median of 3.8 years. RESULTS: Overall, the incidence rate of TB was 10/ 222 = 45.1 (95%CI 24.3-83.9) per 1000 person-years of observation (PYO) among HIV-1-positive participants, compared to 14/2054 = 6.8 (95%CI 4.0-11.5) per 1000 PYO among HIV-1-negative participants (incidence rate ratio 6.62, 95% CI 2.94-14.9). Among the 10 HIV-positive participants who subsequently developed TB disease, the CD4 count was low (median 201/mul, range 45-419), and viral load high (median 4.97 log copies/ml, range 3.70-5.58), at the routine follow-up visit prior to TB diagnosis. Following TB treatment, plasma viral load remained persistently elevated despite clinical resolution of TB disease, and seven of the 10 patients died within a median time of 8 months. CONCLUSION: In this cohort, HIV-infected Ethiopians who developed TB disease already had low CD4 counts and high viral load prior to the diagnosis of TB. Viral load did not decrease following TB treatment, leading to a poor overall prognosis in these patients.