RT Journal Article SR Electronic T1 Determination of cerebrospinal fluid adenosine deaminase activity cut-off for the diagnosis of tuberculous meningitis in Hong Kong JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 800 OP 802 DO 10.1136/jclinpath-2019-206397 VO 73 IS 12 A1 Chan, Toby Chun Hei A1 Chen, Sammy Pak Lam A1 Mak, Chloe Miu A1 Ching, Chor Kwan A1 Luk, Kristine Shik A1 Tsang, Yat Ming A1 Leung, Daniel Cheuk Wa YR 2020 UL http://jcp.bmj.com/content/73/12/800.abstract AB Aims Tuberculous meningitis (TBM) is a severe infection which may lead to serious complication and mortality. Prompt diagnosis and treatment are essential. There is a need for a simple and fast laboratory test to differentiate TBM from other causes.Methods Retrospective review was conducted for cerebrospinal fluid adenosine deaminase (CSF-ADA) activity which was measured at the Chemical Pathology Laboratory of Princess Margaret Hospital, the sole centre providing such service in Hong Kong, for 51 patients with suspected meningitis from nine local hospitals between June 2014 and July 2017. TBM diagnosis was defined by positive culture and/or nucleic acid amplification test result of Mycobacterium tuberculosis complex in CSF.Results CSF-ADA activity was significantly higher in the TBM group (8.6±2.1 IU/L, n=8) than that of the non-TBM group (2.8±5.9 IU/L, n=43). The optimal clinical cut-off of 5.1 U/L for TBM diagnosis in our laboratory yielded 100% sensitivity, 91% specificity, positive likelihood ratio of 10.8 and negative likelihood ratio of 0. In rare circumstance, false elevation may be seen in non-tuberculous cause, such as central nervous system lymphoma and fungal infection.Conclusions We recommend the use of CSF-ADA activity, which is a simple, fast and robust test for early differentiation of TBM from other causes, to facilitate timely initiation of antituberculous treatment and potentially improve patients’ outcome.