Title: Analysis of the Physicochemical State of C-Reactive Protein in Different Preparations Including 2 Certified Reference Materials
Authors: RZYCHON MalgorzataZEGERS IngridSCHIMMEL Heinz
Citation: CLINICAL CHEMISTRY vol. 56 no. 9 p. 1475-1482
Publication Year: 2010
JRC N°: JRC57693
ISSN: 0009-9147
URI: http://www.clinchem.org/cgi/content/abstract/56/9/1475
DOI: 10.1373/clinchem.2010.147124
Type: Articles in periodicals and books
Abstract: BACKGROUND: Standardization of clinical measurements of C-reactive protein (CRP) is based on the availability of reference materials. The serum protein reference material ERM-DA470 was used as a calibrant for various commercially available immunoassays but has now been exhausted. The recently released ERMDA470k/ IFCC was intended to fully replace ERMDA470. However, the new material was not suited for the certification of CRP because of a bias introduced by the lyophilization process that caused loss of about 20% of CRP measurable by routine immunoassays, compared with the nonlyophilized material that was stored in a liquid frozen state. METHODS: Weinvestigated the physicochemical state of CRP in a set of 4 lyophilized and 2 nonlyophilized serum-based CRP-containing materials by semi-native gel electrophoresis, Western blotting, and gel filtration. RESULTS: We detected a monomeric form of CRP (mCRP) in lyophilized materials at a concentration significantly higher than seen in the materials not subjected to lyophilization. Different reconstitution protocols led to variations of the monomeric CRP fraction found in reconstituted, previously lyophilized material. CONCLUSIONS: Most of the 20% loss in measured CRP after lyophilization of the material can be accounted for by the dissociation of natively pentameric CRP into subunits. The observed dissociation results from lyophilization and subsequent reconstitution of the material at insufficient concentration levels of calcium ions. In the presence of various protein forms, differences in antibody specificity and reactivity between immunoassays and alterations of stoichiometry of antigen¿antibody interactions can contribute to the divergence of the measured values.
JRC Directorate:Health, Consumers and Reference Materials

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