Cystatin C in cerebrospinal fluid and multiple sclerosis

Objective: A recent study using surface-enhanced laser desorption/ionization time-of-flight analysis of cerebrospinal fluid identified a 12.5kDa truncated isoform of cystatin C 14 (CysC) as a specific biomarker for multiple sclerosis (MS). Methods: Surface-enhanced laser desorption/ionization time-of-flight analysis of cerebrospinal fluid samples from 43 MS patients and 46 healthy control subjects. Results: Full-length CysC (13.4kDa) concentration was similar in MS and control samples. The 12.5kDa CysC protein was produced from full-length CysC by N-terminal cleavage during storage at -20 degrees C. Interpretation: The 12.5kDa CysC isoform is a storage-related artifact and is not useful as a diagnostic marker for MS.