β-Trace Protein as a Marker for Cerebrospinal Fluid Rhinorrhea

Abstract

Cerebrospinal fluid (CSF) leakage occurs mainly as a complication of head injuries or skull-base surgeries, but may also occur spontaneously or as a result of nontraumatic processes such as inflammatory disorders or tumors (1). Detection and management of CSF leakage is essential to prevent possible life-threatening infections of the central nervous system (2). Radiologic and invasive procedures may be used for the diagnosis of CSF leaks, but these procedures are laborious, expensive, and present potential risk to the patient. Therefore, noninvasive laboratory methods serve as screening procedures before definitive procedures are used to localize the site of the defect. Laboratory assessment of CSF leakage relies on compositional differences between CSF and other body secretions. The β2-transferrin (β2Tr) τ-fraction, or asialotransferrin, is a brain-specific variant of transferrin that lacks neuraminic acid. It therefore can be distinguished from serum transferrin by electrophoretic procedures and used to detect CSF rhinorrhea (3)(4). However, β2Tr is present in aqueous humor and in perilymph fluid and can be detected in serum, especially in chronic alcohol abusers and in patients with inborn errors of glycoprotein metabolism or genetic variants of transferrin (5)(6). β-Trace protein (βTP), recently identified as prostaglandin D2 synthase (7), is another brain-specific protein that is produced mainly in the leptomeninges and the choroid plexus and is secreted into the CSF. βTP is the second most abundant protein in CSF after albumin. However, it is also present in other body fluids, including serum, albeit at much lower concentrations than in CSF (8). Immunoelectrophoretic methods for βTP have been applied as a screening procedure for CSF leaks (9)(10). Recently, a nephelometric assay for the quantification of βTP was introduced that promised several advantages over current CSF detection methods, including enhanced sensitivity and reduced turnaround time (11 …