Diagnostic value of serological tests (IgA, IgG, IgM) against A-60 antigen in tuberculosis

Tuberculosis (TB) is a common infectious disease worldwide especially in developing countries. Diagnosis of TB is difficult and often needs paraclinical studies. Measuring immunoglobulin''s against A-60 antigen of TB microorganism has been reported as a useful technique. The aim of the present study was to evaluate the diagnostic value of serologic test (IgA, IgM, IgG) against A-60 antigen in tuberculosis.Patients and For this case-control study, 176 TB patients (124 patients with smear-positive pulmonary TB and 52 patients with extra pulmonary TB) and 283 healthy controls were enrolled. Then, all subjects were tested for IgM, IgA and IgG against A-60 antigen using ELISA technique. Sensitivities of IgM, IgG and IgA test were 15%, 25% and 40%, respectively while the following specificities were also reported 100%, 75% and 90%, respectively. Positive predictive values (PPV) were 100%, 57% and 72%, however, negative predictive values (NPV) were 65%, 72% and 70%, respectively. Combination of immunoglobulins'' results increased sensitivity, for which the most sensitivity was observed in combination of IgG and IgA results. Our results revealed the usefulness of serologic testing in TB diagnosis. Although its sensitivity is not high enough, combination of immunoglobulin results may improve the sensitivity.