The certification of the mass concentration of beta-2-microglobulin in human serum : ERM-DA470k/IFCC : certification report

This report describes the additional certification of the mass concentration of beta-2-microglobulin (B2M) in ERM-DA470k/IFCC, a human serum material. The material was released in 2008 and was certified for the mass concentration of 12 proteins in human serum. The material is now additionally certified for B2M in accordance with ISO Guide 34:2009. A full description of the processing steps used to produce the material can be found in the first report. The between unit-homogeneity was quantified and the stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The within-unit homogeneity was estimated to determine the minimum sample intake. The material was characterised by an inter-laboratory comparison exercise performed by laboratories of demonstrated competence and with adherence to ISO/IEC 17025. Uncertainties of the certified values were calculated in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties relating to possible lack of homogeneity, instability and to characterisation. The material is intended for the calibration or control, for the certified proteins only, of immunoassay-based in-vitro diagnostic devices or control products. Any other calibrator should be verified as commutable. The material was produced in a similar manner as ERM-DA470, the use of which has led to a significant reduction in the between-method and between-laboratory variation for the proteins certified (B2M was not certified in this material) [ , ]. It was verified during the value assignment procedure that there were no significant matrix effects, and that different methods produced consistent results. The Certified Reference Material (CRM) is available in the lyophilised form of a 1.0 mL portion of serum with additives (4- (2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), sodium azide, benzamidine hydrochloride, sodium chloride and aprotinin). The CRM is available in threaded glass bottles with rubber stoppers and polypropylene screw caps maintained under nitrogen gas. The water mass fraction of the sample is (4.3 ± 0.6) mg/g. The lyophilised powder has to be reconstituted with (1.00 ± 0.01) g of distilled water and the minimum amount of reconstituted sample to be used for B2M measurement is 2 μL. The CRM including its B2M certified value was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.