Certification of Cystatin C in the Human Serum Reference Material ERM-DA471/IFCC - Certified Reference Material ERM®-DA471/IFCC

The production of ERM-DA471/IFCC, certified for the mass concentration of cystatin C, is described. Serum was produced from blood collected in 2 collection centres according to a procedure ensuring that it was obtained from healthy donors, and that the lipid content of the serum was low. The serum was processed, spiked with recombinant cystatin C, and lyophilised. It was verified that the material is homogenous and stable. The material was characterised using a pure protein primary reference preparation (PRP) as calibrant. The PRP was prepared from recombinant cystatin C, and its concentration determined by dry mass determination. The characterisation of ERM-DA471/IFCC was performed by particle enhanced immuno-nephelometry, particle enhanced immuno-turbidimetry and enzyme amplified single radial immuno-diffusion. The certified cystatin C mass concentration in ERM-DA471/IFCC, if reconstituted according to the specified procedure, is 5.48 mg/L, the expanded uncertainty (k = 2) is 0.15 mg/L.JRC.DG.D.2-Reference material

Protein standardization V: value transfer. A practical protocol for the assignment of serum protein values from a Reference Material to a Target Material.

Abstract We present a practical protocol for the assignment of values to serum proteins in a Target Material using a Reference Material. This protocol is based on the model of Direct Value Transfer between serum matrices and is intended to improve the value assignment of commercial calibrators using the Reference Material CRM 470 (now labeled ERM-DA 470) or similar reference materials. The procedure describes the general as well as the practical principles involved in the value assignment (with examples). The practical transfer protocol is based on multiple assays of 6 dilutions of the Reference Material and 6 dilutions of the Target Material. The transfer protocol requires several measurements a day repeated on several days, an important prerequisite being that all reconstitutions and dilutions are controlled by weighing thus reducing uncertainty in the transfer. In open systems that allow the use of the Reference Material as calibrator and the Target Material as samples, the proportionality of the two materials (the presence or absence of matrix effects) can now be directly assessed by evaluating a single regression plot. If no matrix effects are found, the regression line will pass through zero with a slope equal to the ratio of the concentrations of the two materials. In closed systems, the dedicated commercial calibrator has to be used as such; the Reference Material and the Target Material are now assayed as samples against this calibrator. Two regression plots are therefore obtained; if no matrix effects are present among the two materials and the calibrator, both the Reference and Target Materials will show zero intercepts, and the ratio of the two slopes will equal the ratio of the concentrations. Clin Chem Lab Med 2008;46

Standardization of Cystatin C: development of primary and secondary reference preparations.

A Primary Reference Preparation has been produced using pure, recombinant, Cystatin C in a solvent of 0.1 mol/L KCl. Dry mass determination of the Primary Reference Preparation resulted in a Cystatin C concentration of 5.20 g/L. Agarose-electrophoresis and SDS-electrophoresis, as well as N-terminal sequencing, verified the purity, homogeneity and identity of Cystatin C in the Primary Reference Preparation. For the Secondary Reference Preparation, a serum pool was collected and stabilized. A pilot batch was made to verify the selected procedure and spiking with the pure, recombinant Cystatin C. The final Secondary Reference Preparation is now produced (4468 vials) and ready for value assignment and further characterization

Standardizing plasma protein measurements worldwide: a challenging enterprise

The need for harmonizing laboratory results is particularly intense in the field of quantitative protein assays in consideration of the clinical impact of specific protein measurements and their relevance in monitoring disease. We report the efforts made by the Committee on Plasma Proteins of the IFCC Scientific Division to achieve worldwide comparability in plasma protein results. We focus on the production of reference materials and the methods applied throughout their production process. Particularly, the recent characterization of ERM-DA470k/IFCC and ERM-DA472/IFCC has demonstrated that it is possible to reproduce the earlier established procedures and thereby maintain standardization. Plasma protein reference materials have had a substantial impact in improving the harmonization of patient protein results that should translate into better patient care. Clin Chem Lab Med 2010;48:1567-75

First certified reference material for cystatin C in human serum ERM-DA471/IFCC.

The IFCC Working Group for the Standardisation of Cystatin C (WG-SCC), in collaboration with the Institute for Reference Materials and Measurements (IRMM), announces the availability of the new certified reference material ERM-DA471/IFCC. The material was characterised using a pure protein primary reference preparation (PRP) as calibrant. The PRP was prepared from recombinant cystatin C, and its concentration measured using dry mass determination. The characterisation of ERM-DA471/IFCC was performed by particle enhanced immuno-nephelometry, particle enhanced immuno-turbidimetry, and enzyme amplified single radial immuno-diffusion. The certified cystatin C mass concentration in ERM-DA471/IFCC, if reconstituted according to the specified procedure, is 5.48 mg/L, the expanded uncertainty (k=2) being 0.15 mg/L

First Certified Reference Material for Cystatin C in Human Serum ERM-DA471/IFCC

The IFCC Working Group for standardisation of Cystatin C (WG-SCC) in collaboration with the Institute for Reference Materials and Measurements (IRMM) announces the availability of the new certified reference material ERM-DA471/IFCC. The material was characterised using a pure protein primary reference preparation (PRP) as calibrant. The PRP was prepared from recombinant cystatin C and its concentration determined by dry mass determination. The characterisation of ERM-DA471/IFCC was performed by particle enhanced immune-nephelometry, particle enhanced immuno-turbidimetry, and enzyme amplified single radial ummuno-diffusion. The certified cystatin C mass concentration in ERM-DA471/IFCC is 5.48 mg/L, the expanded uncertainty (k= 2) being 0.15 mg/LJRC.D.2-Reference material

Preliminary Commutability Study on Candidate Reference Material for Cystatin C

Plasma (or serum) cystatin C has been proposed as a marker for the glomerular filtration rate, a measure of the capacity of the kidneys to filter plasma (GFR). Several studies, as well as one meta-analysis, have suggested that it is superior to serum creatinine for estimation of GFR. The IFCC working group for the standardisation of cystatin C has, in collaboration with the IRMM, prepared a candidate reference material (RM) for cystatin C. here the results from a preliminary study, performed in order to optimise the design of a planned large-scale commutability study, are presented.JRC.D.2-Reference material

Characterization of the New Serum Protein Reference Material ERM-DA470k/IFCC: Value Assignment by Immunoassay

BACKGROUND: The availability of a suitable matrix reference material is essential for standardization of the immunoassays used to measure serum proteins. The earlier serum protein reference material ERM-DA470 (previously called CRM470), certified in 1993, has led to a high degree of harmonization of the measurement results. A new serum protein material has now been prepared and its suitability in term of homogeneity and stability has been verified; after characterization, the material has been certified as ERM-DA470k/IFCC. METHODS: We characterized the candidate reference material for 14 proteins by applying a protocol that is considered to be a reference measurement procedure, by use of optimized immunoassays. ERM-DA470 was used as a calibrant. RESULTS: For 12 proteins [alpha(2) macroglobulin (A2M), alpha(1) acid glycoprotein (orosomucoid, AAG), alpha(1) antitrypsin (alpha(1)-protease inhibitor, AAT), albumin (ALB), complement 3c (C3c), complement 4 (C4), haptoglobin (HPT), IgA, IgG, IgM, transferrin (TRF), and transthyretin (TTR)], the results allowed assignment of certified values in ERM-DA470k/IFCC. For CRP, we observed a bias between the lyophilized and liquid frozen materials, and for CER, the distribution of values was too broad. Therefore, these 2 proteins were not certified in the ERM-DA470k/IFCC. Different value transfer procedures were tested (open and closed procedures) and found to provide equivalent results. CONCLUSIONS: A new serum protein reference material has been produced, and values have been successfully assigned for 12 proteins. (C) 2010 American Association for Clinical Chemistr

Generation of a New Cystatin C-Based Estimating Equation for Glomerular Filtration Rate by Use of 7 Assays Standardized to the International Calibrator.

Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays