Correlation between culture of Mycobacterium tuberculosis and detection of mycobacterial antigens in cerebrospinal fluid of patients with tuberculous meningitis.

A retrospective study was done to correlate culture of Mycobacterium tuberculosis and detection of mycobacterial antigen in cerebrospinal fluid (CSF) by an inhibition enzyme-linked immunosorbent assay (ELISA). M. tuberculosis was cultured from CSF of 14 out of 70 patients with a clinical diagnosis of tuberculous meningitis (TBM). Mycobacterial antigens were demonstrated in CSF specimens by inhibition ELISA in all 14 culture-positive patients with antigen concentrations of 14.5-295 ng/ml (mean 158.8 ng/ml). Thus there was positive correlation between the detection of mycobacterial antigen and isolation of M. tuberculosis. Based on this observation, 56 CSF specimens from culture-negative patients with clinically diagnosed TBM were examined for mycobacterial antigen and the data were compared with those from culture positive patients. ELISA gave positive results in 38 specimens, with antigen levels of 12.5-280 ng/ml (mean 152.6 ng/ml). In 70 CSF specimens from patients with non-tuberculous neurological disease (control group), ELISA results were negative. Thus, detection of mycobacterial antigen in CSF specimens by inhibition ELISA had a specificity of 100% and a sensitivity of 67.8% for the diagnosis of TBM and is of potential value in the laboratory diagnosis of TBM.