Diagnosis of tuberculous meningitis by immunofluorescence and enzyme immunoassay

Cerebrospinal fluid was collected from 29 patients with tuberculous meningitis, 21 and 7 patients with bacterial and viral meningitis and 5 normal subjects. Pressure, aspect, glucose, protein and cellular content of CSF were studied. Detection of acid fast bacilli in direct film stained by Zeil Neilsen (Z.N.) and fluorochrom (Fl.Ch.) and Culture on Lowenstein Jensen media were done. Then specific immunoglobulin G & M to Mycobacteria were assayed by Immunofluorescence (IF using BCG) and by Enzyme Linked Immunosorbant assay (ELISA) using protein-A of M. Tuberculosis. It was found that diagnosis of M. Tuberculosis by CSF culture was more sensitive than by direct CSF film stained with Z.N. or Fl.Ch. stain (positive in 44.8%, 10.3% and 17.2% of cases respectively). It was noticed that the detection of CSF IgG antibodies was more sensitive than IgM antibodies either by IF or ELISA. By comparing ELISA and IF tests for detection of specific anti-mycobacterial immunoglobulin in CSF, it was clear that the sensitivity and specificity of ELISA was more than IF test. A positive result for antimycobacteria IgG antibodies was obtained in 79.3% and 58.6% of cases respectively (p less than 0.05). None of the CSF of normal controls, bacterial and viral meningitis cases gave positive antimycobacteria IgG by ELISA while 9.5% of the CSF of bacterial and 14.3% of aseptic meningitis cases gave positive results with IF. The sensitivity, specificity and predictive value of the described ELISA test, make it useful for early diagnosis of tuberculous meningitis.