Rapid identification of the Mycobacterium tuberculosis complex by an enzyme-linked immunosorbent assay.

SETTING A medical centre in Taipei, Taiwan. OBJECTIVE To investigate the performance of an enzyme-linked immunosorbent assay (ELISA) using anti-early secreted antigenic target 6 and culture filtrate protein 10 antibodies (MeDiPro Mycobacterium tuberculosis Antigen ELISA) for the detection of M. tuberculosis in positive signals of Mycobacterium Growth Indicator Tubes (MGIT; BACTEC MGIT 960 system). DESIGN A total of 208 consecutive clinical samples, including 185 respiratory specimens and 23 non-respiratory specimens, with positive signals in MGIT were analysed. The assay was performed on Days 1 and 7. The ELISA and conventional culture results were compared. RESULTS Among the tubes with positive signals, 86 (41.3%) were M. tuberculosis, 55 (26.4%) were non-tuberculous mycobacteria and 67 (32.2%) were negative for mycobacteria. The sensitivity of the ELISA for tubes with positive signals (initial smear with positive acid-fast bacilli) on Days 1 and 7 was respectively 75.6% (70.5%) and 96.5% (97.7%), and the specificity was respectively 98.4% (100%) and 100% (100%). CONCLUSION Our results show that the MeDiPro M.tuberculosis Antigen ELISA is a simple, rapid assay (<3 h) for M. tuberculosis antigen detection, especially on Day 7 of incubation with positive signals in the BACTEC MGIT 960 system.