Incidence of tuberculosis and survival after its diagnosis in patients infected with HIV-1 and HIV-2

Background: In sub-Saharan Africa, tuberculosis (TB) is the most frequently diagnosed opportunistic infection and cause of death among HIV-infected patients. HIV-2 has been associated with less immune suppression, slower disease progression and longer survival. Objective: To examine whether the incidence of TB and survival after TB are associated with CD4 cell count rather than HIV type. Methods: Clinical and immunological data were retrospectively evaluated among an open clinic-based cohort of HIV-1- and HIV-2-infected patients to determine incidence of TB (first diagnosis > 28 days after HIV diagnosis) and subsequent mortality. Patients were grouped by CD4 cell count into those with < 200, 200-500 and > 500 × 10⁶ cells/l. Results: Incident TB was diagnosed among 159 of 2012 patients, with 4973 person-years of observation time. In 105/159 (66.0%), the diagnosis was confirmed by direct microscopy or culture. Incidence of TB was highest in the group with < 200 × 10⁶ cells/l (9.1/100 and 8.8/100 person-years in HIV-1 and HIV-2, respectively). Adjusted for CD4 cell count, there was no significant difference in incidence or mortality following TB between HIV-1- and HIV-2-infected patients. Mortality rate was higher inthose with incident TB and HIV infection, most markedly in the group with the highest CD4 cell count (hazard ratio, 10.0; 95% confidence interval, 5.1-19.7). Conclusion: Adjusted for CD4 cell count, incidence of TB was similar among HIV-1-and HIV-2-infected patients. Mortality rates after TB diagnosis were similar in both groups and high compared with those without TB.