Isoelectric focusing in an immobilized pH gradient for the detection of intrathecal IgG in cerebrospinal fluid: sensitivity and specificity for the diagnosis of multiple sclerosis.

Cerebrospinal fluid and serum from 192 patients was analysed for the presence of intrathecally synthesized oligoclonal IgG bands using isoelectric focusing in an immobilized pH gradient pH 7-10. The sensitivity of this method for the diagnosis of multiple sclerosis (MS) was 95% (21 of 22), or 75% if patients with suspected MS were included. The specificity for the diagnosis of MS was 98%, or 96% if the suspected MS patients were included. The very high specificity may be because the intrathecally synthesized oligoclonal IgG associated with MS is more alkaline than IgG from serum and is better detected in an immobilized alkaline pH gradient.