IMMUNOBLOT ANALYSIS FOR SERODIAGNOSIS OF TUBERCULOSIS USING A 45 47-KILODALTON ANTIGEN COMPLEX OF MYCOBACTERIUM-TUBERCULOSIS/

We evaluated the immunoglobulin G (IgG) antibody response to the 45/47 -kDa secreted protein of Mycobacterium tuberculosis by immunoblot assa y, to assess its potential value for serological diagnosis. Control su bjects consisted of healthy volunteers with negative or positive tuber culin skin tests. Most (>98%) scored negative in an immunoblot test wh en the sera were analyzed at a 1:400 dilution, Approximately 40% of se ra (diluted 1 in 400) from tuberculous patients (positive smears) reco gnized the antigen complex. The sensitivity of the test for patients s uffering from extrapulmonary tuberculosis was similar to that for pati ents suffering from pulmonary tuberculosis but who had negative smears , The frequency of positive reactions among the patients suffering fro m other pulmonary diseases was similar to that among the control subje cts. In tuberculous patients infected with human immunodeficiency viru s, the sensitivity of the immunoblot test was significantly lower, Thu s, this test based on an antigen complex used in an immunoblot assay t o detect the presence of IgG antibody has a specificity of 98% and a s ensitivity of 40%, The simultaneous use of different purified antigens , selected at the same high specificity level, may improve the sensiti vity of such an assay.