The incidence of tuberculosis among hiv-positive individuals with high CD4 counts: implications for policy

Background: Intensified case finding (ICF) and earlier antiretroviral therapy (ART) initiation are strategies to reduce burden of HIV-associated tuberculosis (TB). We describe incidence of and associated factors for TB among HIV-positive individuals with CD4 counts > 350 cells/mu l in South Africa. Methods: Prospective cohort study of individuals recruited for a TB vaccine trial. Eligible individuals without prevalent TB were followed up at 6 and 12 months after enrolment. Cox proportional hazards regression was used to determine factors associated with risk of incident TB. Results: Six hundred thirty-four individuals were included in the analysis [80.9 % female, 57.9 % on ART, median CD4 count 562 cells/mu l (IQR 466-694 cells/mu l)]. TB incidence was 2.7 per 100 person-years (pyrs) (95 % CI 1.6-4.4 per 100 pyrs) and did not differ significantly between those on ART and those not on ART [HR 0.65 (95 % CI 0.24-1.81)]. Low body mass index (BMI < 18.5 kg/m(2)) was associated with incident TB [HR 3.87 (95 % CI 1.09-13.73)]. Half of the cases occurred in the first 6 months of follow up and may have been prevalent or incubating cases at enrolment. Conclusions: TB incidence was high and associated with low BMI. Intensified case finding for TB should be strengthened for all HIV positive individuals regardless of their CD4 count or ART status.