Diagnosis of tuberculous meningitis by enzyme-linked immuno-sorbent assay (ELISA), using an affinity chromatography purified mycobacterial antigen.

Using an immunoabsorbent affinity chromatography, a mycobacterial antigen was isolated from culture filtrate of H37Ra Mycobacterium tuberculosis (MTB). The immunoabsorbents were prepared by coupling cynogen bromide-activated Sepharose-4B with human IgG antibody to MTB. Cerebrospinal fluids (CSF) from 10 culture positive, 30 culture negative patients with tuberculous meningitis (TBM) were assayed, for IgG antibody to this mycobacterial antigen by ELISA. CSFs from 50 patients with non-tuberculous neurological diseases were selected as control group. At a selected 'cut off' titre of 1:80, 21 out of 30 CSFs from culture negative patients gave positive results. No false negative result was observed in CSF from 10 culture positive patients with TBM. No false positive results were recorded in CSFs of 50 patients with non-tuberculous neurological diseases. Technical aspects involved in the isolation of this myobacterial antigen and its potential applications in the laboratory diagnosis of TBM have been emphasised in this study.