Value of ELISA using A60 antigen in the serodiagnosis of tuberculosis

This study was set in a general, university hospital in the Canary Islands, with the objective to evaluate an enzyme-linked immunosorbent assay (ELISA) using A60 in the serodiagnosis of tuberculosis. IgG antibody to A60 was determined in 205 patients with active disease [149 culture-positive patients with pulmonary tuberculosis (positive sputum smear 94, negative sputum smear 55) and 56 patients with extrapulmonary tuberculosis], 20 patients with inactive disease, 22 patients with lepromatous leprosy, and 51 controls. The mean levels of anti-A60 antibodies were significantly higher in patients with active disease as compared with controls or patients with inactive disease. Differences were also found between tuberculous patients with pulmonary and extrapulmonary disease. In patients with pulmonary disease, significant differences were detected between smear-positive and smear-negative patients. The overall sensitivity of the test (cutoff 240 ELISA units) was 52.2%. The highest sensitivity was found among smear-positive patients with pulmonary tuberculosis (67%) and the lowest among those with extrapulmonary tuberculosis (32.1%). We conclude that ELISA for the measurement of IgG antibody to Mycobacterium tuberculosis antigen A60 could be of interest, specially in smear-negative cases and extrapulmonary tuberculosis.