Selection, Preparation, and Characterization of Commutable Frozen Human Serum Pools as Potential Secondary Reference Materials for Lipid and Apolipoprotein Measurements: Study within the Framework of the Dutch Project “Calibration 2000”

Abstract

Background: The Dutch project “Calibration 2000” aims at harmonization of laboratory results via calibration by development of matrix-based secondary reference materials. We considered the selection, preparation, and characterization of 34 potential reference materials (PRMs). Methods: Sixteen PRMs were prepared either strictly according to the NCCLS C37-A protocol or in a less stringent and more convenient way. In addition, 18 commercial, so-called human serum-based calibrators or controls were purchased and tested. Lipoprotein integrity was evaluated by examining the physicochemical characteristics of the materials. Commutability of the PRMs was assessed in 86 Dutch clinical laboratories, using a multicenter split-patient-sample between-field-method (twin-study) design. Normalized residuals of the PRMs with respect to the patient regression lines were calculated; in addition, the extra contribution of each PRM to the total measurement uncertainty (CVNetto) was calculated. On the basis of these results, the most native PRM was selected to investigate its potential to reduce interlaboratory variation and to improve lipid and apolipoprotein standardization. Results: In general, only the NCCLS C37-A-type materials displayed normalized residuals below the decision limit for commutability and had small CVNetto values ranging between 0 and 3.8%. This contrasts with the findings in regularly pooled frozen sera and lyophilized cryoprotected PRMs. In two subsequent external quality assessment surveys, the NCCLS type C37-A materials contributed to reducing the intermethod lipid and (apo)lipoprotein variation to ∼2–4%. Conclusions: NCCLS C37-A materials have a strong potential as secondary reference materials, not only for cholesterol but also for HDL-cholesterol, LDL-cholesterol, triglyceride, and apolipoprotein measurements.

Reference distributions for apolipoproteins AI and B and B/AI ratios: comparison of a large cohort to the world's literature

“…This material was released by the International Federation of Clinical Chemists (IFCC), the Community Bureau of Reference (BCR) in Brussels, Belgium (94,95). Recent publications, however, raise some doubt on the issue of commercially available reference materials processed by protocols that are not in accordance with recommendations, which are thus unstable and produce unreliable results (96,97).…”

Recalibration of biochemistry measurements in a multinational cohort study: LIFE course study in CARdiovascular disease Epidemiology (LIFECARE)

“…While there are on-going efforts to harmonize quality assurance performance using commutable materials, i.e. materials without matrix effects, and with a focus on traceability to reference standards, this will take time given the sheer number of laboratories around the world, and impetus from national agencies to adopt such targets [34,35].…”

The European Communities Confederation of Clinical Chemistry and Laboratory Medicine (EC4)

“…Also, EC4 is active in stimulating developments towards harmonisation of numerical laboratory data through the use of common calibrants (commutable secondary reference materials). The Calibration 2000 project in the Netherlands is such a project [8,9], and the lessons learned will be studied for potential pan-European application.…”