Serodiagnosis of tuberculosis using the enzyme-linked immunoabsorbent assay (ELISA) of antibody to Mycobacterium tuberculosis antigen 5.

The serologic response to purified mycobacterial antigen 5 was examined using an enzyme-linked immunoabsorbent assay in 75 patients with pulmonary tuberculosis and 150 control subjects. Two patient and 6 control groups were studied. The serums from the patient groups had significantly higher IgG antibody concentrations than infected control subjects with good specificity. In patients living in low prevalence areas where the results of skin tests in the majority of the population are negative, an antibody titer greater than or equal to 1:40 would have a 95.8% specificity for active disease. For patients living in a high prevalence area where the results of skin tests in the majority of the population are positive, then an antibody titer greater than or equal to 1:40 would have a 79.9% specificity for active disease. Serums from patients with active nontuberculous mycobacterial infection had intermediate mean titers.