Commutability assessment of potential reference materials using a multicenter split-patient-sample between-field-methods (twin-study) design: study within the framework of the Dutch project "Calibration 2000".
BACKGROUND
The Dutch project "Calibration 2000" aims at harmonization of laboratory results via calibration by development of commutable, matrix-based, secondary reference materials. An alternative approach to the NCCLS EP14 protocol for studying commutability of reference materials is presented, the "twin-study design", which in essence is a multicenter, split-patient-sample, between-field-methods protocol.


METHODS
The study consisted of the simultaneous analysis of fresh patient sera and potential reference materials (PRMs) for HDL-cholesterol (HDL-C) by 86 laboratories forming 43 laboratory couples. Six subgroups of method combinations were formed. The patient sera were selected and interchanged by each laboratory couple. The PRMs consisted of three types: C37, prepared according to the NCCLS C37 protocol; Fro, frozen selectively pooled human serum; and Lyo, which was the same serum pool as Fro but lyophilized in the presence of sucrose. All PRMs were provided in three HDL-C concentrations. The regression line residuals for the PRMs were normalized by expressing them as multiples of the state-of-the-art within laboratory SD (SD(SA)). In addition, the extra contribution of each PRM to the total measurement uncertainty, CV(Netto), was calculated.


RESULTS
Averaged over the three PRM concentrations, 1.6% of the C37 residuals were outside the 3 SD(SA) limit. For the Fro and Lyo PRMs, these values were 2.4% and 11.1%. CV(Netto) values for C37, Fro, and Lyo were 2.9%, 4.3%, and 5.3%, respectively.


CONCLUSIONS
The present twin-study design, as a practical alternative to the NCCLS EP14 protocol, is a viable way of studying commutability characteristics of PRMs. The study suggests that the C37 PRMs are the best candidates for a future reference material.
Baadenhuijsen
Henk
H
Dutch Foundation for Quality Assessment in Clinical Laboratories (SKZL), University Hospital Nijmegen, NL 6500 HB Nijmegen, The Netherlands. hbaadenhuijsen@skzl.nl
Steigstra
Herman
H
Cobbaert
Christa
C
Kuypers
Aldy
A
Weykamp
Cas
C
Jansen
Rob
R
D000465:Algorithms; D001800:Blood Specimen Collection; D008076:Cholesterol, HDL / Q000097:blood / Q000592:standards*; D006801:Humans; D009426:Netherlands; D012015:Reference Standards
D008076:Cholesterol, HDL