Performance of nested RT-PCR on CSF for tuberculous meningitis diagnosis in HIV-infected patients

SETTING: Timely diagnosis of tuberculous meningitis (TBM) in patients with human immunodeficiency virus (HIV) infection remains a challenge. Despite the current scale-up of the Xpert® MTB/RIF assay, other molecular diagnostic tools are necessary, particularly in referral centres in low- and middle-income countries without Xpert testing. OBJECTIVE: To determine the diagnostic performance of nested real-time polymerase chain reaction (nRTPCR) in HIV-infected TBM patients categorised according to standardised clinical case definitions. DESIGN: Based on clinical, laboratory and imaging data, HIV-infected patients with suspected TBM were prospectively categorised as 'definite TBM', 'probable TBM', 'possible TBM' or 'not TBM'. We evaluated nRT-PCR sensitivity and specificity in diagnosing TBM among definite TBM cases, and among definite + probable TBM cases. RESULTS: Ninety-two participants were enrolled in the study. nRT-PCR sensitivity for definite TBM (n=8) was 100% (95%CI 67-100) and 86% (95%CI 60-96) for both definite and probable TBM (n=6). Assuming that 'not TBM' patients (n = 74) were true-negatives, nRTPCR specificity was 100% (95%CI 95-100). The possible TBM group (n=4) had no nRT-PCR positives. CONCLUSIONS: The nRT-PCR is a useful rule-in test for HIV-infected patients with TBM according to international consensus case definitions. As nRT-PCR cannot exclude TBM, studies comparing and combining nRT-PCR with other assays are necessary for a rule-out test.