背景结核性脑膜炎（TBM）的及时诊断仍然具有挑战性。分子诊断工具是必要的,特别是在低收入和中等收入国家。目前尚无经批准的商业聚合酶链反应（PCR）测定法可用于检测非呼吸道样本中的结核分枝杆菌，如脑脊液（CSF）。我们旨在验证阈值循环（Ct）的截止点；计算实时PCR检测CSF中结核分枝杆菌（MTbqPCR）的操作特征；以及CSF红细胞（RBC）和总蛋白对MTbqPCR的抑制作用。方法共纳入334名连续参与者。基于临床，实验室和成像数据，可疑TBM病例被归类为明确的，可能,可能或不可能的TBM情况。使用接收器工作特征曲线分析来选择最佳区分Ct值。结果对于分类为明确或可能的TBM病例(n=21)，CSF验证的Ct(≤39.5)提高了MTbqPCR对CSF样本的诊断性能.灵敏度为29%,特异性为95%，阳性预测值为26%，阴性预测值为95%，有效率为90%,阳性可能性为5.3.CSFRBC和总蛋白不影响MTbqPCR的阳性。结论这些数据支持使用CSF样品对TBM诊断的高度特异性但低敏感性的MTbqPCR测定的验证。MTbqPCR有助于诊断，主要与常规微生物学测试和临床算法相关时。
Background Timely diagnosis of tuberculous meningitis (TBM) remains challenging. Molecular diagnostic tools are necessary, particularly in low- and middle-income countries. There is no approved commercial polymerase chain reaction (PCR) assay that can be used to detect Mycobacterium tuberculosis in non-respiratory samples, such as the cerebrospinal fluid (CSF). We aimed to validate the threshold cycle (Ct) cut-off points; calculate the operational characteristics of real-time PCR for detection of M. tuberculosis (MTb qPCR) in the CSF; and the inhibitory affect of CSF red blood cells (RBC) and total proteins on MTb qPCR. Methods A total of 334 consecutive participants were enrolled. Based on clinical, laboratory and imaging data, cases of suspected TBM were categorized as definite, probable, possible or not TBM cases. Receiver operating characteristic curve analysis was used to select the best discriminating Ct value. Results For TBM cases categorized as definite or probable (n=21), the Ct validated for CSF (≤39.5) improved the diagnostic performance of MTb qPCR on CSF samples. The sensitivity was 29%, specificity was 95%, positive predictive value was 26%, negative predictive value was 95%, efficiency was 90% and positive likelihood was 5.3. The CSF RBC and total protein did not affect the positivity of the MTb qPCR. Conclusions These data support the validation of a highly specific but low sensitive MTb qPCR assay for the TBM diagnosis using CSF samples. MTb qPCR contributes significantly to the diagnosis, mainly when associated with conventional microbiology tests and clinical algorithms.
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