The secondary aim was to compare M.  tuberculosis antigen-specific IFNγ responses between the two defined patient groups, that is, individuals with active TB (subsequent smear or culture positive from induced sputa or further samples) and non-active TB (remain culture and smear negative) in an area of high TB prevalence, to determine whether this approach could be pursued to diagnose active TB in HIV-infected patients. The gene discussed is IFNG; the disease is tuberculosis.