TB PCR in the early diagnosis of tuberculous meningitis: evaluation of the Roche semi-automated COBAS Amplicor MTB test with reference to the manual Amplicor MTB PCR test

Abstract

Setting: Cecilia Makiwane Hospital, Mdantsane, Eastern Cape, Republic of South Africa.Objective: To assess the role of the semi-automated Roche COBAS AMPLICORTMMycobacterium tuberculosis PCR test in the diagnosis of tuberculous meningitis (TBM).Design: Eighty-three specimens of cerebrospinal fluid (CSF) were collected prospectively from 69 patients with suspected TBM. The COBAS AMPLICOR TB PCR test was compared with the manual AMPLICORTMTB PCR test, clinical and cerebrospinal fluid (CSF) findings, direct ZN smear and radiometric TB culture.Results: CSF from 7/40 (17.5%) patients treated for TBM were positive by TB COBAS AMPLICORTM. The sensitivity of the test was not significantly different (p=0.375) from the manual TB AMPLICORTMPCR test. The comparative sensitivities of the TB COBAS AMPLICORTMPCR and the manual AMPLICOR PCR for detecting cases of definite and probable TBM from CSF collected within 9 days of commencing antituberculosis treatment were 40% and 60% respectively. All 29 patients not treated for TBM were negative by COBAS AMPLICORTM, giving a specificity of 100%.Conclusion: The COBAS AMPLICORTMTB PCR test is a rapid and highly specific diagnostic test for TBM. However, there was a non-significant trend favouring slightly greater sensitivity using the manual AMPLICORTMTB PCR test.