Serological diagnosis of tuberculosis

To evaluate the efficacy of ELISA for the detection of IgG antibodies against antigen 85 complex (Ag 85 complex) of Mycobacterium tuberculosis. Children of either sex, 0-18 years of age, attending the outpatient department and admitted in the casualty and wards of the Department of Pediatrics, S.N. Medical College, Agra, were included in present study. The study was carried out on children with pulmonary and CNS tuberculosis along with matching controls (83 cases and 32 controls). Informed consents of their parents or guardians were taken. They were subjected to clinical examination, relevant laboratory investigations, tuberculin test and chest radiograph. Relevant body fluids were subjected to bacteriological tests; ELISA was applied to serum samples for detection of IgG antibodies against antigen 85 complex (Ag85). The result of ELISA was compared with bacteriological tests [Ziehl Neelson (ZN) staining for acid-fast bacilli, culture on Lowenstein Jensen (LJ) medium and culture on BacT/Alert 3D system]. ELISA tests showed a significantly higher sensitivity (59.1%) as compared with LJ medium culture method (19.3%), BacT/Alert 3D system (24.1%) and ZN staining (16.9%) in all patients (p < 0.001). Specificity of ELISA test was 71.9%. In view of the convenience, low cost and good sensitivity, ELISA tests have a promising future in the diagnosis of childhood tuberculosis.