Serodiagnostic contributions of antibody titers against mycobacterial lipid antigens in mycobacterium avium complex pulmonary disease

Background. Although the incidence of pulmonary tuberculosis is decreasing, the number of immunocompetent patients with Mycobacterium avium complex (MAC) pulmonary disease is steadily increasing. Therefore, albeit not contagious, MAC pulmonary disease needs to be diagnosed rapidly and accurately. We examined the serodiagnostic contributions of serum immunoglobulin G antibody titers against the species-specific and -common mycobacterial lipid antigens in the diagnosis of MAC pulmonary disease. Methods. Serum samples were obtained from 65 patients with MAC pulmonary disease, 15 patients with suspected MAC disease, 25 patients with pulmonary tuberculosis, 10 patients with Mycobacterium kansasii disease, and 100 healthy volunteers (control subjects). We measured the serum immunoglobulin G antibody titers against trehalose monomycolate (TMM-M) and apolar-glycopeptidolipid (GPL), lipid antigens extracted from MAC. Results. In patients with MAC pulmonary disease, the antibody titers against TMM-M and apolar-GPL were significantly higher than those in the other patient groups or in the control subjects. By receiver operator characteristic curve analysis, an optical density of 0.27, corresponding to the optimal cutoff antibody titer against TMM-M, was associated with a sensitivity of 89.2% and a specificity of 97.0%, and an optical density of 0.33, corresponding to the optimal cutoff antibody titer against apolar-GPL, was associated with a sensitivity of 89.2% and a specificity of 94.0%. Conclusions. Measurements of antibody titers against TMM-M and apolar-GPL would be useful in the diagnosis of MAC pulmonary disease and in the differential diagnosis of mycobacterial pulmonary disease.