Slide agglutination test for the diagnosis of pulmonary and extra-pulmonary tuberculosis

Objective: Evaluation of a 2 min slide agglutination test to detect the presence of antibodies directed against Mycobacterium tuberculosis antigens. Design: The test utilizes solible antigens extracted from a cultivable new species of non-pathogenic saprophytic mycobacterium, Mycobacterium w, which shares antigenic determinants with M. tuberculosis. The soluble antigens are covalently linked to carboxylated polystyrene latex beads. Results: The sensitivity of the assay was increased from 78% (reported earlier), to 90.2% for pulmonary tuberculosis and 85.7% for extra-pulmonary tuberculosis. The specificity of the test was determined by testing the sera of apparently healthy controls, and patients with other respiratory tract infections and rheumatoid arthritis. Among the apparently healthy controls, 7.3% tested positive. None of the sera from the patients with other diseases gave positive agglutination. Conclusion: This simple and rapid technique could be suitable for mass screening for pulmonary and extrapulmonary tuberculosis.