Comparative assay of immunoglobulins by two methods Immunoprecipitation: turbidimetry and nephelemetry

Abstract

Our objective in this study was to compare turbidimetry and nephelometry using the automat Cobas 400 plus (Roche Diagnostics^TM) and the semi-automat Minineph (Binding-SiteTM). The study was based on the determination of sera collections (IgG, IgA, IgM) of 150 samples each. Every fifty sera belong to respectively, patients affected by a humoral congenital
immunodeficiency, young subjects without such deficiency and healthy adult.  The rates of concordance of the results showed a significant difference in the concentration rate between those methods, confirmed by an agreement coefficient K between fair (K = 0,06 à K = 0,239) and moderate (Kappa = 0,48).
The high the immunoglobulin concentration, the worst the concordance between the two assays. An improved method standardization will probably reduce differences.