Diagnostic significance of humoral immune responses to recombinant antigens of Mycobacterium tuberculosis in patients with pleural tuberculosis.

Mycobacterium tuberculosis bacilli are seldom demonstrated in tuberculous pleural effusion (TPE) by conventional bacteriological methods. In this study, an indirect enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG against four mycobacterial recombinant antigens (ESAT-6, PlcA, HspX and Tb8.4) in 69 pleural fluids of patients with TPE and 71 patients with malignant pleural effusion. To increase the sensitivity of the assay, a multi-antigen cocktail containing all the above antigens were also used. IgG positivity in ELISA for PlcA, HspX, Tb8.4, ESAT-6 antigens and multi-antigen complex were 49.3, 60.8, 49.3, 53.6 and 75.4% respectively. Each one of the above four antigens and their multi-antigen cocktail were highly specific in distinguishing tuberculous and malignant pleural effusion. This new generation immunoassay will serve as a useful marker for the diagnosis of pleural tuberculosis patients in whom M. tuberculosis bacilli were not demonstrated by bacteriological methods. J. Clin. Lab. Anal. 24:283-288, 2010.