Early diagnosis of tuberculous meningitis by polymerase chain reaction

Rapid detection of Mycobacterium tuberculosis is of vital importance for patients with tuberculous meningitis. We evaluated an improved polymerase chain reaction (PCR) technique for rapid and specific identification of M tuberculosis in CSF.

The technique was used on CSF samples from 42 patients (3 of whom were human immunodeficiency virus seropositive) with clinical symptoms, signs and laboratory findings suggestive of tuberculous meningitis. The target for amplification was a nucleotide sequence located within IS6110. A small amount of DNA from M smegmatis strain 1008, containing a modified IS6110, was added in the PCR as a control for inhibitors and to quantitate the PCR for M tuberculosis.

On the basis of symptoms and clinical findings, antituberculous treatment was started in 35 patients, but was later stopped in 11 because of lack of response. From 12 patients responding to treatment and with a positive diagnostic test, 11 cases were detected by PCR, nine cases were culture positive, and two cases microscopy positive. Of the remaining 12 patients who had negative CSF by microscopy, PCR, and culture, 11 were diagnosed as having tuberculous meningitis on the basis of the response to treatment (three had active pulmonary tuberculosis) and one had mycobacteria other than M tuberculosis in sputum and urine. The sensitivity of the PCR was 48% in those with a final diagnosis of tuberculous meningitis (culture or PCR confirmed cases, plus those with clinical evidence and who responded to antituberculous treatment), which is much higher than the 9% sensitivity of microscopy. There were no false-positive PCR results.

PCR on CSF is a rapid method for the accurate diagnosis of tuberculous meningitis.