A predictive score followed by nucleic acid amplification for adult tuberculous meningitis diagnosis in Southern Brazil

From 2012 to 2013, 300 adults under investigation of tuberculous meningitis (TBM) were tested with polymerase chain reaction (PCR) in central spinal fluid (CSF), followed by TBM score calculation. There were 33(11%) confirmed TBM cases based on clinical findings, CSF-culture; biopsy/necropsy exams and clinical improvement after tuberculosis specific treatment. Other 267 adults were classified as non-TBM. Based on the original score there were 143 possible cases (6 ≤ score ≤ 11) and 20(60.6%) out of 33 TBM; among 27 probable TBM (score ≥ 12) there were 13/33 (39.4%) confirmed cases. The CSF-PCR detected 48% (16/33) of TBM. Based on these findings, a new cut-off point was proposed to differentiate probable (score ≥ 10) from possible (6 ≤ score ≤ 9) TBM. After score adjustment, there were 61 probable TBM with 26/33 (78.8%) TBM, and among the 109 possible TBM there were 7/33(21.2%) confirmed cases. In both systems, there were 130 non-TBM (score ≤ 5) and no confirmed TBM. The association of adjusted score (≥ 10) and CSF-PCR showed high sensitivity (90.9%) and specificity (86.9%), positive and negative predictive value of 46.2% and 98.9%, respectively. The combination of CSF-PCR and TBM score is a useful tool for the management of adults under investigation of TBM, but the best cut-off point may need local/regional adjustments.