Improved serodiagnosis of tuberculosis using two assay test.

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Abstract
An antigen capture immunoassay was developed for the detection of mycobacterial antigens in sera from patients with tuberculosis. The assay was evaluated together with an antibody measuring enzyme immunoassay in a clinical trial for serodiagnosis of tuberculosis. Sensitivity of the antibody assay for active pulmonary tuberculosis, including relapsed infections, was 75%, and specificity with other lung diseases was 97%. Sensitivity for extrapulmonary tuberculosis was 84.5% and specificity 84%. Sensitivity of the antigen assay for active tuberculosis was 45% with no false positive reactions. Combination of the results from the two assays increased total sensitivity to 96.5% with a positive predictive value of 0.81 and a negative value of 0.98. The two assay test was relatively simple to perform and offered improved serological diagnosis of tuberculosis over a single antibody test.