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, years) were studied, including age +/- SD 12.0 +/- 5.0 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 U, U, U, and U, respectively ( M. abscessus - 718 +/- 342 193 +/- 113 129 +/- 49 121 +/- 53 infected patients vs. each of the other groups, P < .005). The A60 IgG test was both sensitive (similar to 87%) and specific (similar to 95%) if adapted cutoff values were used ( 150 U and 250 U for patients aged less than or equal to 10 years and patients aged 110 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.