Polymerase chain reaction for the rapid diagnosis of tuberculous meningitis

(i)

The study was carried out with the aim to evaluate a polymerase chain reaction (PCR) based on the amplication of a 169 bp DNA fragment specific for the Mycobacterium tuberculosis complex for the rapid diagnosis of tuberculous meningitis (TBM). (ii)

A total of 105 CSF specimens from clinically suspected cases of TBM were studied. Clinical details of the cases and cytochemical parameters of the CSF specimens were recorded. In addition to the 105 specimens, 10 CSF specimens from cases other than TBM, 4 non-mycobacterial culture isolates (1 strain of E. coli, 1 strain of Proteus species and 2 strains of Salmonella species) and 1 sample of sterile distilled water were processed as negative controls. For positive control standard culture of Mycobacterium tuberculosis H37Rv was processed with every batch of specimens. Besides PCR, smear for AFB by the Ziehl Neelsen Carbol Fuchsin (ZNCF) and the fluoro chrome method and culture on LJ medium was also carried out. (iii)

By PCR, 31.42% specimens were found positive, whereas by conventional culture on LJ medium only 3.8% specimens were positive. Only 1.9% specimens were found to be smear positive by the fluorochrome staining method, while none was positive by the ZNCF method. The PCR results showed complete correlation with the clinical findings of the patients. (iv)

The PCR was found to be superior to the currently available techniques for the diagnosis of tuberculous meningitis in terms of sensitivity, specificity and rapidity and could play a critical role in the diagnosis of suspected cases.