Interprétation de l’index IgG et du diagramme de Reiber par Protis 2 dans les maladies inflammatoires du système nerveux central

Abstract

Summary Intrathecal humoral immune response is a common feature of many inflammatory diseases of the central nervous system. IgG intrathecal synthesis demonstration is a cornerstone for the early diagnosis of multiple sclerosis. Immunoglobulin (Ig) synthesis is correlated with CSF-specific oligoclonal bands detection after isoelectric focusing. It may also be performed in calculating Ig index (Ig LCR/ Ig blood × albumin LCR/albumin blood) and comparing it to a limit defined thanks to the studies of Professor Reiber. Quantitative technics have the advantage to be quickly realised but isoelectric focusing is the gold standard. Formula and Reibergram allow to quantify the IgG, IgA and IGM synthetised in central nervous system and to follow their evolution. Softwares put IgG index on the graph and generate data interpretation for the clinical chemist. Fiability of the comments is variable according to the used software and the position of the index on the graph. We compare IgG intrathecal synthesis detection with the new program of Siemens, Protis 2, and the oligoclonal bands detection with isoelectric focusing on 330 samples. Protis 2 has a great specificity (98%) and a low sensitivity (50%). His positive likelihood ratio is 25 and his negative likelihood ratio, 0.5. It is only reliable when it predicts an intrathecal immune response. It may never be used like a screening test or for exclude an IgG intrathecale synthesis. The usefulness of the software for the follow up of IgG, IgA and IgM in infectious disease of central nervous system is only evocated in this study.