Humoral immune response against 38-kDa and 16-kDa mycobacterial antigens in tuberculosis

Several ELISA tests based on mycobacterial antigens have been used for the rapid diagnosis of tuberculosis (TB), although demonstration of Mycobacterium tuberculosis in a smear or culture is the most reliable method. In the present study, the diagnostic value of 16-kDa and 38-kDa mycobacterial antigens was investigated in patients who were diagnosed with tuberculosis by clinical and/or bacteriological findings in Turkey. The PATHOZYME-TB Complex Plus commercial ELISA kit was used for measuring immunoglobulin G against 38-kDa and 16-kDa recombinant antigens. Humoral immune response was analysed in a group of 179 TB patients (143 smear-positive, 19 smear-negative, eight lymphadenitis and nine pleuritis), 15 inactive TB cases and in control groups consisting of 40 healthy volunteers and 20 subjects with pulmonary diseases other than TB. The sensitivity, specifity, positive predictive value and negative predictive value of the test were determined at 52.5%, 93.3%, 95.9% and 39.7%, respectively in TB cases. Antibodies were detected at above cut-off level in three (20%) out of 15 subjects with inactive TB. In conclusion, the ELISA test has a very good specifity and an acceptable sensitivity and positive predictive value. It is thought that it could be used in combination with other methods to increase diagnostic accuracy, especially for culture-negative tuberculosis cases, which are difficult to diagnose.