Specific and early detection of IgG, IgA and IgM antibodies to Mycobacterium tuberculosis 38kDa antigen in pulmonary tuberculosis

The objective was to apply the purified 38kDa protein antigen of Mycobacter ium tuberculosis in ELISA to estimate the IgG, IgA and IgM antibody levels in sera and circulating immune complexes of tuberculosis patients. Sera fro m smear and culture positive tuberculosis patients were positive for anti 3 kDa IgG, IgA and IgM antibodies, with a sensitivity of 61%, 30% and 10%, re spectively, and with a specificity of 100% for IgG. The sensitivity of the test improved to a level of 68% for IgG + IgA and of 71.4% for IgG + IgA IgM without significantly compromising the specificity (IgG of 100%, IgG IgA of 96%, IgG + IgA + IgM of 90%). Among the smear, culture-negative but X-ray-positive cases, 60% were serum positive for IgG antibody, while in sm ear-negative but culture-positive cases, 54% were positive for IgG antibody . Measurement of 38kDa antibodies showed a greater than 95% sensitivity in smear and culture-positive, and smear-negative and culture-positive patient s, through a combination of assays for serum IgG and circulating immune com plex antibodies, while the specificity was 100%. (C) 2001 Harcourt Publishe rs Ltd.