目的：探讨结核感染T细胞斑点试验（T-SPOT.TB）中结核特异性抗原孔（TBAg）斑点形成细胞数与阳 性对照孔植物血凝素（PHA）形成斑点数的比值（TBAg/PHA ratio）对结核性脑膜炎（TBM）的早期诊断价值。 方法：收集疑似TBM患者148例，入院24 h内采集脑脊液进行常规、生化及病原微生物检测，同时采集外周静 脉血进行T-SPOT.TB检测。结果：148例患者中最终纳入131例（88.5%），其中TBM 组为55例，非TBM组为 76例。TBM组的T-SPOT.TB试验阳性率高于非TBM组（P<0.05），诊断TBM的敏感性为81.8%，特异性为 76.3%。当采用0.07作为TBAg/PHA比值的截断值时，诊断TBM的敏感度、特异度和ROC曲线下面积分别 为78.2%、92.1%、0.871。结论：采用TBAg/PHA比值法可显著提高T-SPOT.TB诊断TBM的特异性。

To determine the performance of the ratio of Mycobacterium tuberculosis-specific antigen (TBAg) to phytohaemagglutinin (PHA), (TBAg/PHA ratio), in T-SPOT.TB assay for early diagnosis of tuberculous meningitis (TBM). Methods: A total of 148 patients with suspected TBM were prospectively recruited. Cerebrospinal fluid (CSF) samples were obtained for routine, biochemical, and microbiological tests within 24 hours of admission. Peripheral venous blood samples were also collected for T-SPOT.TB assay. Results: 131 out of 148 (88.5% ) patients had a final definitive diagnosis, with 55 cases being diagnosed TBM group and 76 cases being diagnosed non-TBM group. The positivity rate of T-SPOT.TB assay in the TBM group was significantly higher than that in the non-TBM group (P<0.05). Using T-SPOT.TB assay, the sensitivity and specificity in diagnosing TBM were 81.8% and 76.3%, respectively. Using 0.07 as the cutoff value of TBAg/PHA ratio, the sensitivity, specificity, and area under the ROC curve (AUC) in the diagnosis of TBM were 78.2%，92.1%，0.871, respectively. Conclusion: Calculation of the TBAg/PHA ratio showed important clinical value for early diagnosis of TBM based on its increased specificity.