Evaluating the Commutability of Reference Materials for α-Fetoprotein: Accurate Value Assignment With Multiple Systems and Trueness Verification.

Background: The accurate measurement of α-fetoprotein (AFP) is critical for clinical diagnosis. However, different AFP immunoassays may yield different results. Appropriate AFP reference materials (RMs) were selected and assigned accurate values for applications with external quality assessment (EQA) programs to standardize AFP measurements. Methods: Forty individual clinical samples and six different concentrations of candidate RMs (Can-RMs, L1-L6) were prepared by the Beijing Center for Clinical Laboratories. The Can-RMs were assigned target values by performing five immunoassays, using WHO International Standard 72/225 as a calibrator, and sent to 45 clinical laboratories in Beijing for AFP measurements. The commutability of all RMs was assessed based on CLSI and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) approaches. Analytical performance was assessed for compliance based on accuracy (total error, TE), trueness (bias), and precision (CV). Results: The Can-RMs were commutable for all immunoassays using the CLSI approach and for 6 of 10 assay combinations using the IFCC approach. RMs diluted in WHO RM 72/225 were commutable among all assays with the CLSI approach, except for serum matrix (Autolumo vs. Roche analyzer) and diluted water matrix (Abbott vs. Roche/Mindray analyzer), whereas some inconclusive and non-commutable results were found using the IFCC approach. The average pass rates based on the TE, bias, and CV were 91%, 81%, and 95%, respectively. Conclusions: The commutability of the RMs differed between both evaluation approaches. The Can-RMs exhibited good commutability with the CLSI approach, suggesting their suitability for use with that approach as commutable EQA materials with assigned values and for monitoring the performance of AFP measurements.