Gel isoelectric focusing and IgG index for demonstration of intrathecal IgG synthesis in neurological disorders.

Cerebrospinal fluid (CSF) and serum were obtained from 37 patients with multiple sclerosis and from 112 patients with various other neurological diseases, and the concentrations of IgG and albumin were quantitated immunochemically. Simultaneously, isoelectric focusing (IF) was carried out for the detection of CSF-specific oligoclonal bands in the alkaline region. CSF-specific components were found in 51 patients by IF, the estimated number of which correlated significantly (Rs = 0.733, p less than 0.0001) with the value of the IgG index. In addition, six patients without CSF-specific abnormalities on IF had an increased IgG index (greater than 0.70). In two of them this increase is, in all probability, false-positive; three others showed fully identical IF bands in both CSF and serum. On the other hand, 13 of the same 51 patients showed a normal IgG index (less than 0.70) although CSF-specific components were detectable on IF. These results confirm the superiority of IF over the immunochemical quantitation of albumin and total IgG for the evaluation of immune reactivity in the central nervous system.