Cerebrospinal fluid and blood assays of diagnostic usefulness in multiple sclerosis.

Although the ultimate diagnosis of multiple sclerosis (MS) still remains clinical, confirmatory laboratory aids can be of marked assistance, especially in early and atypical cases. Whereas numerous tests have been described, the only ones to withstand scrutiny in numerous laboratories have been various immunoglobulin assays and myelin basic protein measurements in the cerebrospinal fluid (CSF). Of the newer assays that are commercially available and readily adapted to routine clinical laboratory use, the most discriminating are the production of a CSF IgG:albumin ratio, using an electroimmunodiffusion method, and agarose electrophoresis of concentrated CSF to demonstrate oligoclonal IgG bands. Together, these assays can be performed on less than 3 ml of CSF, and will show relatively specific abnormalities in over 95% of clinically definite MS patients. They both detect abnormalities that frequently occur in the course of disease, and thus add considerable weight to the clinical impression of MS.