Measurement of Immunoglobulin G against Mycobacterial Antigen A60 in Patients with Cystic Fibrosis and Lung Infection Due to Mycobacterium abscessus

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Abstract
Background. The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis. Methods. We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60. Results. A total of 186 patients with cystic fibrosis (mean age ± SD, 12.0 ± 5.0 years) were studied, including 15 M. abscessus—positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus—infected patients), 7 M. abscessus—positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (±SD) for these 4 groups were 718 ± 342 U, 193 ± 113 U, 129 ± 49 U, and 121 ± 53 U, respectively (M. abscessus—infected patients vs. each of the other groups, P < .005). The A60 IgG test was both sensitive (∼87%) and specific (∼95%) if adapted cutoff values were used (150 U and 250 U for patients aged ⩽10 years and patients aged >10 years, respectively) and correlated well with results of acid-fast bacilli smears. Conclusion. Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.