Predictive values of β-trace protein (prostaglandin D synthase) by use of laser-nephelometry assay for the identification of cerebrospinal fluid

OBJECTIVE: beta-Trace protein (beta-TP) is an immunological marker for the detection of cerebrospinal fluid traces. The aim of the study was to evaluate the predictive values of a new research assay for beta-TP. METHODS: A total of 154 specimens from patients with otorrhea or rhinorrhea were investigated for cerebrospinal fluid (CSF) by use of a laser-nephelometric assay for beta-TP. Samples were obtained between January 1994 and November 2000. A sample was reported to be positive for CSF when the beta-TP concentration was more than 6 mg/L. Case evaluations were performed retrospectively and tabulated for indication, clinical course, additional investigations, surgical procedure, and follow-up. RESULTS: beta-TP was detected in 16 specimens; 138 samples were negative for beta-TP with a value less than 3 mg/L. One sample was suggestive of CSF traces at 4.6 mg/L. In correlation with the clinical course, the intraoperative findings, intraoperative visualization with sodium fluorescein, high-resolution computed tomography of the paranasal sinuses or the petrous bone, computed tomographic cisternography, magnetic resonance imaging, and radionuclide cisternography, there was no false-positive result. On four occasions, false-negative results occurred, with an overall accuracy of 0.974. The beta-TP test had a negative predictive value of 0.971 and a positive predictive value of 1. CONCLUSION: Analysis of beta-TP via the nephelometric assay is a valuable and reliable test in cranial base surgery for the identification of CSF.