Evaluation of the IS6110 PCR assay for the rapid diagnosis of tuberculous meningitis

Abstract

Background: Tuberculous meningitis (TBM) is one of the common clinical manifestations of extra-pulmonary tuberculosis. It is difficult to diagnose due to a lack of rapid, sensitive, and specific tests. Newer methods, which are easy and reliable, are required to diagnose TBM at an early stage. Thus our aim was to evaluate the polymerase chain reaction (PCR) technique, using primers directed against the IS6110 gene, for the detection of Mycobacterium tuberculosis in the CSF, for the diagnosis of TBM patients.

Methods: An in-house IS6110 PCR method using a specific pair of primers designed to amplify the insertion sequence, IS6110, in the M. tuberculosis genome was used to analyze CSF. A total of 80 CSF samples from different groups of patients were studied (confirmed TBM n = 35, clinically suspected TBM n = 16, non-TBM infectious meningitis n = 12, non infectious neurological diseases n = 17).

Results: PCR gave a sensitivity of 91.4% and specificity of 75.9% for the diagnosis of TBM in patients with TBM confirmed by culture. In 16 clinically diagnosed, but unconfirmed, TBM cases PCR was positive in 10 (62.5%) cases. There were seven (24.1%) PCR-positive cases among the 29 patients with non-TBM and non-infectious neurological disease.

Conclusion: We conclude that the performance of an in-house IS6110 PCR assay is valuable in the rapid diagnosis of tuberculous meningitis.

Figure 1

Amplification of the 123 bp product of M. tuberculosis by PCR. PCR products were analyzed by electrophoresis on 2% agarose gel. M represents 100 bp DNA ladder. L1: positive control DNA (M. tuberculosis strain H₃₇Rv). L2, L4, L6: clinically positive TBM samples. L3, L5: non-TBM samples. L7: negative control.