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Serodiagnosis of Mycobacterium avium–Complex Pulmonary Disease Using an Enzyme Immunoassay Kit

¹ Department of Internal Medicine, National Hospital Organization (NHO) National Toneyama Hospital, Toyonaka-shi, Osaka, Japan; ² Department of Immunology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan; ³ Department of Clinical Laboratory Medicine, Graduate School of Medicine, Kyoto University, Kyoto-shi, Kyoto, Japan; ⁴ Department of Internal Medicine, NHO Kinki-chuo Chest Medical Center, Sakai-shi, Osaka, Japan; ⁵ Department of Medicine, Osaka Prefectural Medical Center for Respiratory and Allergic Diseases, Habikino-shi, Osaka, Japan; ⁶ Department of Laboratory Medicine, Saitama Medical Center, Jichi Medical University, Saitama-shi, Saitama, Japan; and ⁷ Department of Internal Medicine, Sakamoto Hospital, Toyonaka-shi, Osaka, Japan

Correspondence and requests for reprints should be addressed to Seigo Kitada, M.D., Department of Internal Medicine, National Hospital Organization National Toneyama Hospital, 5-1-1 Toneyama, Toyonaka-shi, Osaka 560-8552, Japan. E-mail: kitadas{at}toneyama.hosp.go.jp

Rationale: The diagnosis of Mycobacterium avium–complex pulmonary disease (MAC-PD) and/or its discrimination from pulmonary tuberculosis (TB) is sometimes complicated and time consuming.

Objectives: We investigated in a six-institution multicenter study whether a serologic test based on an enzyme immunoassay (EIA) kit was useful for diagnosing MAC-PD and for distinguishing it from other lung diseases.

Methods: An EIA kit detecting serum IgA antibody to glycopeptidolipid core antigen specific for MAC was developed. Antibody levels were measured in sera from 70 patients with MAC-PD, 18 with MAC contamination, 37 with pulmonary TB, 45 with other lung diseases, and 76 healthy subjects.

Measurements and Main Results: Significantly higher serum IgA antibody levels were detected in patients with MAC-PD than in the other groups (P < 0.0001). Setting the cutoff point at 0.7 U/ml resulted in a sensitivity and specificity of the kit for diagnosing MAC-PD of 84.3 and 100%, respectively. Significantly higher antibody levels were also found in patients with nodular-bronchiectatic disease compared with fibrocavitary disease in MAC-PD (P < 0.05). There was a positive correlation between the extent of disease on chest computed tomography scans and the levels of antibody (r = 0.43, P < 0.05) in patients with MAC-PD.

Conclusions: The EIA kit is useful for the rapid diagnosis of MAC-PD and for differentiating MAC-PD from pulmonary TB and, if validated by studies in other populations, could find wide application in clinical practice.

Key Words: nontuberculous mycobacteria • immunocompetence • sensitivity and specificity

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The diagnosis of pulmonary disease due to ubiquitous Mycobacterium avium complex (MAC) is complicated, and requires clinical findings together with repeatedly positive sputum culture. What This Study Adds to the Field An enzyme immunoassay kit for measuring human serum antibody to glycopeptidolipid core antigen specific for MAC was developed. The kit is useful for the serodiagnosis of MAC pulmonary disease and could find wide application in clinical practice.

 

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