The levels of serum IgA antibody to GPL core antigen were signifi cantly higher in the MAC-PD group than in the non-MAC disease group ( P , .0001). The sensitivity and specifi city for diagnosing MAC-PD were 78.6% and 96.4%, respectively. GPL 5 glycopeptidolipid; MAC 5 Mycobacterium avium complex; MAC-PD 5 M avium complex pulmonary disease.