Place de l'immunofixation des IgG du LCR dans le diagnostic de sclérose en plaques (SEP)

Abstract

We presented the analytical and diagnostic performances of immunofixation for detection of oligoclonal IgG bands in native unconcentrated cerebrospinal fluid (CSF) and diluted serum samples analysed in the same run on Hydragel 6 CSF Sebia on Hydrasys ® Sebia, an alternative to the manual technique of IgG isoelectric focusing (IEF). Pairs of CSF and serum of 124 patients studied over a 2 year period were classified in: 29 definite multiple sclerosis (MS) 35 possible MS, 11 inflammatory neurological diseases other than MS, and 49 non-inflammatory diseases of the central nervous system. Pairs of CSF and serum of 98 patients were tested by isoelectric focusing for control of intrathecal IgG synthesis. The analytical performances of the two techniques to reveal IgG oligoclonal bands are practically identical. The sensivity of immunofixation is 96%, of isoelectric focusing is 93%. Their specificity is 93% and 96%, respectively. The positive predictive value to establish diagnosis of MS is 90% with immunofixation and 92% with isoelectric focusing. The negative predictive value to exclude diagnosis is 97% with immunofixation and 96% with isoelectric focusing. The interpretation of IgG immunofixation is in practice more difficult than IgG isoelectric focusing, the procedure is easy and quick to perform.