Evaluation of IgG, IgA and IgM against Mycobacterial Antigen in Patients with Extrapulmonary Tuberculosis

Abstract

Tuberculosis (TB) is a specific infectious disease usually caused by the tubercle bacillus, Mycobacterium tuberculosis (MBT). It primarily affects the lungs and causes pulmonary tuberculosis (PTB) and when it affects other organs it is known as extrapulmonary tuberculosis (EPTB). The diagnosis of TB largely depends on case history, clinical examination, radiological finding and subsequent laboratory confirmation by bacteriological examination. But the radiological findings are not specific and the sensitivity of AFB (acid fast bacilli) smear is poor. To overcome this difficulty, various serological tests have been tried. A novel antigen namely A60 antigen was found to be highly immunogenic and this present study was carried out to see the diagnostic significance of the ELISA test for A60 antigen in diagnosing extrapulmonary tuberculosis. The study was designed as a cross-sectional study involving both extrapulmonary TB patients and controls. Their serum immunoglobulins (IgG, IgA and IgM) specific toA60 antigen were measured by enzyme linked immunosorbent assay (ELISA) technique. In this study, IgG, IgA and IgM was significantly elevated among the EPTB patients as compared to the controls and the IgA and IgM ELISA test combinations was most ideal in diagnosing EPTB. Keywords: Tuberculosis, Extrapulmonary tuberculosis, AFB (acid fast bacilli), A60 antigen, ELISA (enzyme linked immunosorbent assay), Immunoglobulin.