[Diagnostic value of IgG antibody levels against 38 kDa mycobacterial antigen]

Tuberculosis diagnosis bases on clinical and radiological symptoms and identification of mycobacteria. Accuracy of both methods is limited. Therefore reliable serological test would have considerable advantage. The present study was aimed at evaluating IgG-mediated immune response against specific mycobacterial antigens 38 kDa in group of 200 patients and control subjects. Our material consisted of 104 tuberculosis patients, 25 with sarcoidosis, 24 with lung cancer, 13 with bacterial or fungal pulmonary infection, 8 with mycobacterial infections other than tuberculosis and 26 healthy persons. We used commercially available ELISA based kits (Pathozyme TB-complex). Specificity of 100% and sensitivity of 49% was achieved. Sensitivity increased to 59% in chronic cases and to 52% in culture positive cases. Sensitivity decreased to only 14% in group of new culture negative cases. Measurement of IgG serum level against 38 kDa can be helpful in tuberculosis diagnosis. As the test lacks falsely positive results it indicates its high positive predictive value.