Appropriate use of the Xpert® MTB/RIF assay in suspected tuberculous meningitis.

We disagree with the recommendation by the World Health Organization to use Xpert(®) MTB/RIF on cerebrospinal fluid for the initial diagnosis of tuberculous meningitis (TBM). TBM is a devastating disease requiring empirical treatment even when the probability of disease is low. We suggest that a useful TBM diagnostic test needs a negative predictive value (NPV) of ⩾ 99% so that empirical treatment can be stopped safely. The NPV of Xpert is around 84%, making a negative test of limited value. While better tests are awaited, a composite score, possibly combining Xpert with clinical variables and with high NPV, should be constructed and validated prospectively.