Background: An enzyme immunoassay (EIA) kit detecting serum IgA antibody to Mycobacterium avium complex (MAC)-specific glycopeptidolipid (GPL) core antigen has been used in Japan. However, this EIA kit has not been evaluated in other population. Methods: To evaluate the usefulness of this kit, antibody levels were measured in sera from each 40 patients with MAC-pulmonary disease (MAC-PD) and M. abscessus complex-pulmonary disease (MAB-PD), 20 patients with pulmonary tuberculosis (PTB), and 20 healthy controls. Results: Significantly higher levels were detected in patients with MAC-PD than in the other groups. However, patients with MAB-PD also had higher level than patients with PTB and healthy controls. In cohort without MAB-PD patients, the discriminatory power was extremely high (area under the curve [AUC], 0.98; 95% CI, 0.95-1.00) with sensitivity of 87.5% and specificity of 100% at cutpoint of 0.69 U/ml. In cohort with MAB-PD patients, however, the discriminatory power was weaken to 0.83 of AUC (95% CI, 0.76-0.90) with sensitivity of 72.5% and specificity of 82.5% at cutpoint of 1.70 U/ml. In the setting for detection of MAC-PD and MAB-PD from the others, the AUC was 0.96 (95% CI 0.92-0.99) with sensitivity of 85.0% and specificity of 100% at cutpoint of 0.52 U/ml. Conclusions: The EIA kit could be used for differentiating MAC- or MAB-PD from PTB, not for diagnosis of MAC-PD in Korea.