[SERODIAGNOSIS OF THE MYCOBACTERIUM AVIUM COMPLEX BY USING IgA ANTIBODIES FOR THE GLYCOPEPTIDOLIPID CORE ANTIGEN].

Purpose: The diagnosis of Mycobacterium avium complex pulmonary disease (MAC-PD) can be challenging. A serodiagnosis enzyme immunoassay (EIA) kit, which detects the serum anti-glycopeptidolipid (GPL) core IgA antibody, has been commercialized recently; however, its clinical usefulness in the diagnosis of MAC-PD is still unclear. This study aimed to evaluate the availability of this kit and identify factors affecting testing accuracy.

Methods: We performed a retrospective study of 195 patients who were evaluated with an EIA kit at Nagasaki University Hospital between November 2012 and March 2014.

Results: 12 of 16 (75.0%) MAC patients have underlying diseases ; 8 of 16 (50%) had complications associated with respiratory diseases. There were no significant differences between the seropositive and seronegative background of patients with confirmed MAC-PD. Regarding the accuracy of serodiagnosis EIA kit, its sensitivity and specificity were 81.3% and 88.3% (with a cut-off value of 0.7 U/ml), respectively. Of false-positive patients with bronchiectasis, 28.6 % demonstrated a good response to anti-MAC treatment, indicating that the sensitivity of the EIA kit might be higher than that of culture-based diagnosis because patients with clinically diagnosed MAC-PD were included in the false-positive population.

Conclusions: In the current study, the serodiagnosis EIA kit demonstrated good sensitivity and specificity for the diagnosis of MAC-PD. Further clinical investigations are necessary to clarify the role of this kit in definitively diagnosing MAC infections.