Background: Diagnosis of tuberculous meningitis (TBM) is hampered by the lack of rapid and accurate diagnostic tools. We evaluated the immunological response to Mycobacterium tuberculosis anti-A60 antibodies in cerebrospinal fluid (CSF) in comparison to adenosine deaminase (ADA) determination, for the diagnosis of TBM.
Methods: A total of 63 CSF samples were analyzed by indirect ELISA for the detection of anti- A60 IgG, IgM and IgA. These include samples from 17 patients with confirmed TBM and 46 control patients with other infections.
Results: The mean individual anti-A60 IgM, IgG and IgA CSF antibody titers were significantly higher in TBM in comparison with control groups (p < 0.01). The best discriminatory CSF antibody for confirming TBM diagnosis was IgM, with an area under the receiver operating characteristic curve of 0.928 (95%CI 0.834-0.978), compared to 0.863 (95% CI: 0.752-0.936) for ADA testing (p = NS). The sensitivity of anti- A60 IgM CSF antibody titers (cutoff > 0.06 U/ml) was 94.1% compared to 88.2% for ADA (cutoff > 6.2 U/ml), p = NS. Both anti A60 IgM and ADA showed the same moderate specificity (80.4%). Two cases of TBM were correctly identified by anti-A60 IgM but missed by ADA.
Conclusion: The ELISA test for anti-antigen A60 antibodies (IgM) is a rapid and sensitive tool for the rapid diagnosis of TBM that can be a complement to ALDA determination. The specificity of both tests is still a limitation in TBM diagnosis.