The value of cerebrospinal fluid immunoglobulin analysis in clincial neurology.

The IgG index (formula: see text) corrects for the influence of serum protein abnormalities as well as a bloodbrain barrier damage and is, therefore, a better measure for the presence of an IgG elevation in CSF due to IgG synthesis, when compared with other IgG quotients commonly used. Agar gel electrophoresis of CSF for demonstration of oligoclonal IgG is probably superior to the determination of the IgG index when a diagnosis of MS is suspected. Determination of kappa and lambda light chain antigenic determinants in CSF, and calculation of the kappa/lambda ratio may also be used to demonstrate the occurrence of oligoclonal CSF immunoglobulins. An abnormal ratio can, however, be demonstrated only in 50% of MS patients and has, therefore, at present no place as a routine diagnostic method when MS is suspected.