Enzyme-linked immunosorbent-assay for antigen detection in tuberculous meningitis

Two systems of Competitive Enzyme linked immunosorbent assay (ELISA) were developed to detect Mycobacterial antigen in cerebrospinal fluid (CSF) for the diagnosis of tuberculous meningitis (TBM)--one by using indigenously prepared Anti-M.tuberculosis H37Rv-Penicillinase conjugate (Method I) and another by using commercially available Anti M. bovis BCG-Horse Radish Peroxidase (HRP) conjugate--(Method II). The tests were used to analyse CSF of 148 patients clinically confirmed as having TBM and 278 control subjects. By using > or = 10 ng/ml as the cut-off value for Method I and > or = 1 ng/ml as that for Method II, the specificity for both were 100% and positivity was 79.73% and 67.57% respectively. A follow up study in 26 TBM cases after 2 weeks (16 cases), 4 weeks (13 cases) and 4-12 months (10 cases) of antituberculous treatment revealed that mycobacterial antigen persisted in the majority of cases even after 4 weeks of the treatment.