COMPARISON OF A TUBERCULIN INTERFERON-GAMMA ASSAY WITH THE TUBERCULINSKIN-TEST IN HIGH-RISK ADULTS - EFFECT OF HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

A novel, whole blood interferon-gamma (IFN-gamma) assay was evaluated to determine its suitability for detecting Mycobacterium tuberculosis exposure in intravenous drug users with or without human immunodeficie ncy virus (HN) infection, Whole heparinized blood was incubated overni ght in separate. wells with tuberculin purified protein derivative (PP D), saline, and mitogen controls, Levels of IFN-gamma in plasma supern atants were determined by rapid ELISA, Participants were then administ ered the tuberculin skin test (TST) and tested for cutaneous anergy. T he whole blood IFN-gamma test agreed (89%-100%) with a positive TST in both HIV-seropositive and -seronegative subjects, but reactivity to P PD was more detectable by the whole blood assay among those with negat ive TSTs or anergy, TST induration diameter and IFN-gamma responses we re correlated (Spearman's p = .45, P = .0001), but both responses were blunted by HIV infection, In summary, tuberculin reactivity appears t o be more detectable by the whole blood IFN-gamma assay than by TST, a nd the assay requires no return visit for test reading.