[Usefulness of antibodies against A60 mycobacterial antigen in tuberculosis diagnosis]

Diagnosis of tuberculosis is based on clinico-radiological symptoms and on identification of mycobacteria. Accuracy of both methods is limited. Therefore reliable serologic test would have considerable advantage. The goal of our study was to evaluate serologic response against A60 mycobacterial antigen in group of 270 patients (pts) (137 pts with active tuberculosis (TB), 15 pts with mycobacterial infections other than TB (MOTT), 58 pts with sarcoidosis, 26 pts with lung cancer and 34 healthy controls. We used commercially available ELISA based kits against antigen A60 (ANDA-TB). Specificity of 87% for IgG, of 94% for IgA and for IgM, of 85% for IgG + IgA, of 89% for IgA + IgM, of 80% for IgG + IgM, and of 79% for IgG + IgA + IgM was achieved. Sensitivity of 40% for IgG, of 30% for IgA, of 18% for IgM, of 56% for IgG + IgA, of 35% for IgM + IgA, of 50% for IgG + IgM, and of 59% for IgG + IgA + IgM was obtained. The results demonstrated that humoral response differs depends on the immunoglobulin class. Measurements of IgG or IgG and IgA as most sensitive against A60 are potentially more useful serological tests in clinical practice. It is not recommended to use tests based on antigen A60 for differentiation tuberculosis and MOTT.