Isoelectric focusing is superior to immunofixation electrophoresis in diagnosing CNS inflammation

Background - A sensitive method to detect intrathecal IgG production is important in diagnosing inflammatory central nervous system (CNS) diseases, including multiple sclerosis (MS). Objective - To compare cerebrospinal fluid (CSF) electrophoresis with isoelectric focusing (IEF), immunofixation-peroxidase electrophoresis (IFPE) and high-resolution agarose electrophoresis with protein-staining (HRAGE). Methods - Paired serum and CSF samples from 307 consecutive patients attending a general neurology clinic were examined with IEF, IFPE and HRAGE. Clinical diagnosis was based on review of the patients' medical records after an average of 4 years. Results - The sensitivity for detecting any inflammatory (autoimmune or infectious) CNS disease (52 patients) was 67% for IEF, 50% for IFPE and 29% for HRAGE. The sensitivity for detecting MS (14 patients) was 93%, 86% and 29% respectively. The sensitivity for detecting clinically isolated syndrome (eight patients) was 75%, 25% and 13% respectively. The number of oligoclonal bands in IEF was higher in inflammatory than in non-inflammatory neurological diseases or symptoms, but similar in MS and other inflammatory diseases. Conclusion - IEF is the method of choice in diagnosing intrathecal IgG synthesis.