Detection of cerebrospinal fluid leakage by isoelectric focusing on polyacrylamide gels with silver staining using the PhastSystem

Abstract

Cerebrospinal fluid (CSF) leakage, which sometimes occurs after skull trauma, is a life-threatening condition. A prompt start with antibiotics and/or prompt surgical treatment of fistulas is essential to avoid severe complications. This requires a fast and reliable method for detecting CSF leakage. This paper describes a fast (< 2 h) method based on the identification of the tau protein (beta 2-transferrin) band(s). Tau protein is a brain-specific variant of transferrin that is characteristic of CSF. The method includes iso-electric focusing (IEF) on pre-cast polyacrylamide gels and silver staining using the PhastSystem, an automated instrument for electrophoresis and staining. In the present study, this technology was applied on 200 consecutive CSF samples, 32 of which were from healthy volunteers. Tau protein was detected in all CSF samples but 5 (2.5%), all of which were from patients with blood-brain barrier (BBB) damage. In these cases, the tau protein band was indistinct when direct silver staining was used. Therefore, immunofixation with an antitransferrin antibody was performed, and after that the tau protein band was easy to detect. The specificity of the method was high, since no brain-specific tau protein band was detected in serum, tears, saliva, or nasal secretion. As IEF of CSF using the PhastSystem is increasingly used as the routine method for detection of oligoclonal bands of IgG in neurological disorders, it could readily be used in the clinical (neuro) chemical laboratory also for the less frequent cases of suspected CSF leakage.