Nontuberculous Mycobacterium Infections in Rheumatoid Arthritis Patients: The Serodiagnosis of Pulmonary Disease due to Mycobacterium avium Complex with an Enzyme Immunoassay Kit Detecting Glycopeptidolipid Core Antigen (Capilia MAC Antibody ELISA)®.

Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms that can cause various diseases, including pulmonary disease (PD). In patients with rheumatoid arthritis (RA), numerous pulmonary manifestations, including bronchiectasis, may develop into Mycobacterium avium-complex (MAC)-PD, which can be lethal in patients who are being treated with a tumor necrosis factor-alpha blocker. However, the bronchiectasis associated with NTM-PD is difficult to distinguish from that associated with RA by radiological imaging alone. In addition, the diagnosis of NTM-PD is often hampered by the ease of NTM contamination. For the serological diagnosis of MAC-PD, the enzyme immunoassay (EIA) kit, Capilia MAC Antibody ELISA®, determines the levels of serum IgA antibody to the glycopeptidolipid core of MAC. Here we describe the efficacy of this EIA kit for diagnosing MAC-PD, and we review the characteristics of NTM and the association between RA patients and NTM infections.