Diagnosing tuberculous meningitis from cell-free DNA by multi-targeted real-time PCR: An experience from 170 cases.

SETTING

and objective: To evaluate the diagnostic utility of Cell-free DNA (Cf-DNA)-based multi-targeted real-time PCR (Mrt-PCR) for diagnosing tuberculous meningitis, the most severe form of extrapulmonary tuberculosis.

DESIGN

A total of 170 cerebrospinal fluid samples (CSF) of tuberculous meningitis [Definite TBM (n = 146), Probable TBM (n = 24)] and 100 non-TB controls were subjected to Cf-DNA Mrt-PCR test using IS6110, IS1081, and nrdZ gene targets. The performance was also evaluated against Truenat MTB Plus assay and GeneXpert MTB/RIF Ultra.

RESULTS

The sensitivity, specificity, positive predictive value and negative predictive value of Cf-DNA M-rtPCR was 78.24 %, 100 %, 100 % and 72.99 %, respectively in overall diagnosis of TBM and 82.88 %, 100 %, 100 % and 80 %, respectively in diagnosing 'definite' TBM. Cf-DNA M-rtPCR detected 14 additional cases that were missed by Truenat MTB Plus assay and GeneXpert MTB/RIF Ultra. Among the different gene targets used, eight cases were detected only by IS1081, three only by IS6110 and one only by nrdZ gene. Six cases were reported rifampicin-resistant by both Truenat MTB Plus assay and GeneXpert MTB/RIF Ultra and were also confirmed by rpoB sequencing.

CONCLUSION

The detection of cell-free DNA, along with M-rtPCR could serve as a reliable tool for diagnosing tuberculous meningitis directly from CSF samples.