Genus and species-specific IgG and IgM antibodies for pulmonary tuberculosis.

Objective: To evaluate three different enzyme immunoassays for serological diagnosis of pulmonary tuberculosis and to compare their diagnostic accuracy in different combinations.

Design: A non-interventional comparative study.

Place And Duration Of Study: The study was carried out at the Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi between April and September 2001.

Subjects And Methods: Sera from patients suffering from pulmonary tuberculosis (n=94) with sputum positive for acid fast bacilli (AFB) and sera from control group of healthy individuals (n=90) with sputum negative for AFB were tested by Pathozyme-Myco G EIA, Pathozyme-TB Complex Plus EIA and Pathozyme Myco M EIA kits for the genus-specific IgG and IgM, and the species-specific IgG antibodies against antigens of Mycobacterium tuberculosis.

Results: The detection of IgG against genus-specific antigens by Pathozyme-Myco G had a sensitivity of 46% and a specificity of 93%, of IgG against species-specific antigens by Pathozyme-TB Complex Plus had a sensitivity of 64% and specificity of 97% and of IgM against genus-specific antigens by Pathozyme Myco M had a sensitivity of 67% and specificity of 98%. When the results of these immunoassays were evaluated in combination, their sensitivity improved. Combination of genus-specific IgM and species-specific IgG yielded best results with a sensitivity of 87% and specificity of 93%.

Conclusion: The sensitivity of serological diagnosis of tuberculosis is low, but it can be increased by utilizing a combination of several antigens.