Oligoclonal bands in cerebrospinal fluid: a comparative study of isoelectric focusing, agarose gel electrophoresis and IgG index

Objective - To compare the sensitivity and specificity of isoelectric focusing (IEF) with immunofixation, agarose gel electrophoresis (AGE) and the IgG index in detecting intrathecally synthesized IgG in multiple sclerosis (MS) and in other nervous system disorders. Materials and methods - Cerebrospinal fluid (CSF) and serum from 147 patients with various nervous system diseases, 20 of whom had MS, were compared with IEF, AGE and the IgG index. Results - CSF-restricted oligoclonal bands (OCB) were found in 20 of 20 patients with MS using IEF and in 9 of 20 using AGE. OCB were found in 12 patients with other nervous system disorders (OND) using IEF and 4 using AGE. The mean IgG index was 0.50 in OND and 0.96 in MS (P < 0.0001). Of 20 MS patients, 9 had an IgG index above the defined cut-off value of 0.72. Conclusions IEF is about twice as sensitive as AGE in detecting OCB in MS. IEF is also far superior to the IgG index in determining intrathecal IgG synthesis.