Tuberculosis among HIV-infected population: incidence and risk factors in rural Tanzania

Background: The incidence of tuberculosis among HIV-infected populations with high CD4 count in high burden countries has not been well studied.
Objective: To assess the TB incidence in HIV-infected adults and its associated risk factors.
Method: A cohort study with retrospective review of medical records and prospective follow-up of HIV-infected adult participants attending CTC who were 18-55 years old, had CD4 count more than 250 cells/mm³ in the period of 2008-2010 and were not on ART at enrolment. Cox proportional hazard regression was used to explore the predictors of incident TB.
Results: Overall 777 (24%) of 3,279 CTC enrolled HIV-infected adults fulfilled the inclusion criteria of the study. The incidence of TB in the study population ranged from 0.8/100 per person years (PY) at risk (95% CI 0.5-1.3) in the main analysis to 1.7/100 PY at risk (95% CI 1.0-2.6) in sensitivity analyses. Only prior history of TB disease was found to have a significant association with an increased risk of TB, hazard ratio 5.7 (95% CI 2.0-16.4, p value 0.001).
Conclusion: Tuberculosis incidence among HIV-infected adults with medium/high CD4 count in Bagamoyo is lower than in other high TB burden countries. Previously TB treated patients have a much higher risk of getting TB again than those who never had TB before.