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

Said K, Verver S, Kalingonji A, Lwilla F, Mkopi A, Charalambous S, Reither K

1. Ifakara Health Institute, Bagamoyo Research and Training Centre, P O Box 74, Tanzania
2. Swiss Tropical and Public Health Institute, Socinstrasse 57, 4002, Basel, Switzerland
3. University of Basel, Petersplatz 1, 4003 Basel, Switzerland
4. KNCV Tuberculosis Foundation, and Amsterdam Institute of Global Health and Development, Academic Medical
Centre Amsterdam, The Netherlands
5. Department of Public Health, Erasmus MC, Rotterdam, The Netherlands
6. District AIDS Coordinator, CTC, Bagamoyo District Hospital, Bagamoyo, Tanzania
7. Aurum Institute, 29 Queens Road, Johannesburg, 2194, South Africa

Abstract
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/mm 3in 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.

Keywords: Tuberculosis, HIV, Care and Treatment Center, CD4 cell count