Serum glycopeptidolipid core IgA antibody levels in patients with chest computed tomography features of mycobacterium aviumintracellulare complex pulmonary disease

Abstract

Measurement of serum glycopeptidolipid core IgA antibody (GPL antibody) was recently reported to show a high sensitivity and specificity for diagnosing Mycobacterium avium-intracellulare complex (MAC) pulmonary disease (MAC-PD), but its clinical value has not been confirmed. This study aims to evaluate the seropositive rate in patients with suspected MAC-PD based on chest computed tomography (CT), and to examine whether GPL antibody reflects the extent of lung involvement on CT or the number of bacteria in sputum, retrospectively. Among 66 patients with suspected MAC-PD on CT, 36 patients were negative for MAC by culture and 30 were positive. Sputum grades of MAC were evaluated by fluorochrome microscopy of sputum smears. The lungs were divided into six regions to assess the extent of disease. Serum levels of GPL antibody were measured with an enzyme immunoassay (cut-off value >0.7 U/ml). The GPL antibody positive rate was 19.4% among patients who were negative for MAC by culture versus 73.3% among culture positive patients. The serum level of GPL antibody was significantly correlated with the sputum smear grade (r=0.43, p less than 0.05) and was also correlated with the number of lung regions showing MAC-PD features on CT (r=0.43, less than 0.05). Some MAC-PD patients may have CT features of MAC with positive level of GPL antibody, although the diagnosis cannot be confirmed by culture. GPL antibody levels reflect the pulmonary burden of MAC, as assessed from the sputum smear grade and number of involved regions on chest CT.