Finding patients eligible for antiretroviral therapy using TB services as entry point for HIV treatment

To estimate the proportion of antiretroviral therapy (ART) eligible adults (15-49 years) with tuberculosis potentially identifiable through tuberculosis services using a CD4 count below 350 cells/mm3 as cut-off value for ART initiation.

Using TB notification rate data, HIV seroprevalence data, and estimates of the size of the adult population (15-49 years) in 18 sub-Saharan African countries with an HIV seroprevalence of > 5%, calculations of the number of ART eligible adults with tuberculosis presenting to tuberculosis services were made. Assumptions were made on the tuberculosis notification rates in the age-group 15-49 years, the HIV-infected population with a CD4 count below 350 cells/mm3 and the relative risk of developing tuberculosis, and average duration from HIV infection to death. The probability of having a CD4+ count below 350 cells/mm3 given a diagnosis of tuberculosis was estimated using Bayes' theorem, and estimates of the number of patients with a CD4 count below 350 cells/mm3 identifiable through tuberculosis were made. The number needed to screen to identify one ART eligible patient through tuberculosis services was estimated for each country.

ART eligible adults with tuberculosis potentially identifiable through tuberculosis services in the 18 countries ranged from 2% to 18% of the total HIV-infected adult population with a CD4+ count below 350 cells/mm3 and would average 10% of all such HIV patients. The number needed to screen to identify ART eligible patients through tuberculosis services ranged from 1.4 to 4.2, against 8.6 to 65.4 if adults aged 15-49 are randomly screened for low CD4 counts.

Tuberculosis services are an important entry point for identifying ART eligible patients. Given that dually infected patients identified through tuberculosis services contributed to 10% of the HIV-infected adult population with a CD4 cell count below 350 cells/mm3 in the 18 sub-Saharan African countries, major efforts are required beyond the tuberculosis services in detecting patients that should benefit from ART. However, the low number needed to screen gives opportunity to use tuberculosis services in AIDS control and ART scaling-up programmes.