Cut-off value for ß-trace protein (ß-TP) as a rapid diagnostic of cerebrospinal fluid (CSF) leak detection

Abstract

OBJECTIVE: To find an adequate cut-off point for beta trace protein (¿-TP) in nasal secretion (NS) and validate this diagnostic test with a large sample of patients. Likewise, we evaluated ¿-TP test efficacy to confirm the cerebrospinal fluid (CSF) leakage closure after treatment. METHODS: We performed a retrospective analysis with 207 samples from 162 patients with suspected CSF leakage received in the Hospital Universitario Virgen de la Arrixaca between 2010 and 2016. Twenty-five samples were included in the control group. Samples were obtained from NS through a swab to determine ¿-TP using a nephelometry-based assay. Sensitivity, specificity, and area under the curve (AUC) for ¿-TP in NS were assessed using the receiver operator characteristic (ROC) analysis. RESULTS: Using imaging techniques, the diagnosis of CSF leak was confirmed in 57 patients (35.19%), while 105 had a negative diagnosis (64.81%). Patients with CSF leakage had significantly higher ¿-TP values in NS (16.07-±-16.94-mg/L, p-<-.001) than the control group (0.33-±-0.12-mg/L) and patients without CSF leakage (0.61-±-2.34-mg/L). Applying a 1-mg/L cut-off point resulted in 96.5% sensitivity and 97.1% specificity. Positive and negative predictive values (PPV and NPV) at this cut-off were 94.9% and 98.6%, respectively. Finally, this cut-off point yields a test efficacy for CSF leak diagnosis of 97% (95% CI 92.9-98.9). CONCLUSION: Our study has established a 1-mg/L ¿-TP concentration in NS as a cut-off point for CSF leakage diagnosis with high sensibility and specificity. These results suggest that ¿-TP analysis could be useful to check CSF leak resolution. LEVEL OF EVIDENCE: 4.