Beta-trace protein levels in epidural fluid and cerebrospinal fluid: a comparative analysis

BACKGROUND: Distinguishing cerebrospinal fluid (CSF) from epidural fluid is important when the origin of aspirated fluid is uncertain during neuraxial procedures. We evaluated the discriminative ability of β-trace protein (BTP). METHODS: Epidural samples were obtained via epidural catheters after local anesthetic administration, and CSF samples during spinal anesthesia. Glucose, total protein, and BTP were measured, and receiver operating characteristic (ROC) analyses were performed. RESULTS: BTP levels were markedly higher in CSF than in epidural samples, with no overlap. Glucose overlapped between groups, whereas total protein showed limited differences. ROC analysis demonstrated excellent discrimination for BTP (AUC = 1.000) under the present study conditions, outperforming glucose (AUC = 0.904) and total protein (AUC = 0.633). For glucose, the optimal cutoff was 56.5 mg/dL (sensitivity 83.3%, specificity 90.0%). For BTP, any cutoff between 0.42-4.03 mg/L achieved 100% sensitivity and specificity within this dataset. CONCLUSIONS: BTP shows strong discrimination between CSF and epidural fluid.