Bandes oligoclonales et index IgG interprété selon Reiber dans les maladies inflammatoires du système nerveux central

IgG intrathecal synthesis (IS) detection is useful for the diagnosis of inflammatory diseases of the central nervous system (CNS) like multiple sclerosis (MS). This is demonstrated by CSF-spécific oligoclonal IgG detection (OB) and by a IgG index increase. IgG index is the quotient between QIgG (CSF-IgG/ serum-IgG) and Qalbumin (CSF-albumin/serum-albumin). We compared the performances of two Dade-Behring software which facilitates the interpretation: SEPP based on the Fateh Moghadam diagram and Protis based on Reiber diagram. Analyses were performed among 270 patients with CNS inflammatory disease symptoms. The data were classified in 2 groups according to wether the number of red blood cells in CSF was lower (N: 225) or higher (N: 45) than 30 red blood cells/mm3. In comparison with OB detection, SEPP detected IS with a sensitivity, specificity, predictive positive value and predictive negative value of 87, 83, 57 and 97% and Protis of 76, 97, 85 and 94% for CSF without red cells. The sensibility, specificity, predictive positive value and predictive negative value fall to 36, 76, 33 and 78% for SEPP and to 27, 91, 50 and 79% for Protis when CSF contains more than 30 red blood cells. Even a weak blood contamination decreases the reliability of quantitative technics. The erroneous comments are observed when the intersection between QIgG and Qalbumin is on a line of the diagram. Owing to poor sensitivity, the quantitative technics are not able to replace OB detection. Their principal interest for the clinician is the short delay of results and a rapid confrontation of magnetic resonance with a possible IS.