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

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 (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged <or=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.