Gene Xpert MTB/RIF assay in patients with clinical suspicion of tuberculous meningitis

Early diagnosis and treatment of tubercular meningitis (TBM) is one of the best predictors of survival. The smear testing of the cerebrospinal fluid (CSF) has a low sensitivity and cultures, though having higher sensitivity, take a long time in TBM diagnosis. The present study was done to evaluate the proportion of positive Gene Xpert test, a rapid nucleic acid amplification test, in clinically suspected patients with TBM. The results of Gene Xpert tests were then compared with the culture results. One hundred and fifty prospective patients with a clinical suspicion of TBM were classified as probable or possible TBM and underwent CSF examination for culture and Gene Xpert assay. Out of 124 patients available for statistical evaluation, 52 were in the probable and 72 in possible TBM group. The proportion of patients with Gene Xpert positivity were significantly more in probable compared to possible TBM (63.15% vs 36.85%, p<0.001). Twenty-eight patients had a positive culture result. The sensitivity of Gene Xpert relative to culture testing was 68.42%, specificity of 97.61%, a positive predictive value of 92.85% and a negative predictive value of 87.23%. Gene Xpert testing provided a rapid diagnosis in patients suspected with TBM. The high sensitivity and specificity of this test relative to culture testing is a strong indication that it should be included as one of the gold standard tests in patients with suspected TBM.