Tuberculosis contacts but not patients have higher gamma interferon responses to ESAT-6 than do community controls in The Gambia

The Mycobacterium tuberculosis antigen ESAT-6 has been proposed for tubercu losis immunodiagnosis. In The Gambia, 30% of community controls produced ga mma interferon (IFN-gamma) in response to ESAT-6. Increased proportions of responders and intensities of responses were found in household contacts. R esponses that were initially low in tuberculosis patients increased after t reatment. An ESAT-6 IFN-gamma assay will be of limited use in the diagnosis of tuberculosis in countries where tuberculosis is endemic. Its role in co ntact tracing should be evaluated further.