Oligoclonal bands and the IgG index in multiple sclerosis: uses and limitations

The relationship between two tests commonly used in the investigation of multiple sclerosis (MS), the IgG index and oligoclonal bands, has been assessed. Using an immunoblotting technique specific for IgG, analysis of cerebrospinal fluid for oligoclonal bands was found to provide greater diagnostic sensitivity than the IgG index without any loss of specificity. In patients without oligoclonal bands the IgG index had no diagnostic value for MS and in the presence of bands the magnitude of the index was unrelated to the clinical certainty of the diagnosis. High values of the IgG index were invariably associated with the presence of oligoclonal bands and the IgG index appeared to have no clinical significance independent of this relationship. Even as a screening test the IgG index has serious limitations.