Evaluation of IgA-mediated humoral immune response against the mycobacterial antigen P-90 in diagnosis of pulmonary tuberculosis.

BACKGROUND Serologic methods for diagnosis of tuberculosis have been widely investigated owing to their low cost and rapid technical execution. Sensitivity and specificity of different tests have been reported to be largely variable. STUDY OBJECTIVES To evaluate the IgA-mediated humoral immune response against the mycobacterial antigen P-90 as a tool for diagnosis of pulmonary tuberculosis. PARTICIPANTS Eighty-eight patients with microbiologically confirmed diagnosis of pulmonary tuberculosis (32 with positive sputum smears and 56 with negative sputum smears), 28 patients with a definite nontuberculous lung disease, 12 subjects with healed tuberculosis, and 47 healthy volunteers (24 purified protein derivative negative and 23 positive). MEASUREMENTS AND RESULTS Detection of anti-P-90 IgA was performed by enzyme-immunoassay. At a cutoff of 0.221 optical density, determined by a receiver operating characteristic curve, the overall sensitivity and specificity of the test were 70.4% and 91.9%, respectively. Patients with active tuberculosis showed significantly higher titers of anti-P-90 IgA compared with other groups (p < 0.05). CONCLUSIONS The evaluation of IgA-mediated humoral immune response against the antigen P-90 might constitute a useful tool for presumptive diagnosis of pulmonary tuberculosis.