Ann Lab Med.  2024 Nov;44(6):507-517. 10.3343/alm.2023.0447.

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

• Zhang J
• Zhao J
• Wang Q
• Zhang R
• Yue Y

• KMID: 2560797
• DOI: http://doi.org/10.3343/alm.2023.0447

Abstract

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.

Keyword

Alpha-fetoprotein; Commutability; External quality assessment; Immunoassay; Reference standard

Figure

• 

  Fig. 1 Comparability of the results obtained when the WHO72/225 standard was diluted in six different buffer matrices and tested using five different alpha-fetoprotein immunoassays. Panels A–F show the results obtained with six different buffer matrices, including (A) phosphate-buffered saline, (B) a healthy human serum pool, (C) DMEM, (D) minimal essential medium, (E) Roswell Park Memorial Institute 1640 medium, and (F) distilled water.

• 

  Fig. 2 Assessing the commutability of reference materials across five analytical systems for determining alpha-fetoprotein concentrations based on the CLSI document EP30-A method. (A) Roche assay results – Abbott assay results. (B) Roche assay – Beckman assay. (C) Roche assay – Mindray assay. (D) Roche assay – Autolumo assay. (E) Abbott assay – Beckman assay. (F) Abbott assay – Mindray assay. (G) Abbott assay – Autolumo assay. (H) Beckman assay – Autolumo assay. (I) Beckman assay – Mindray assay. (J) Autolumo assay – Mindray assay. The solid black lines are regression curves, and the dashed lines are two-tailed 95% prediction lines.

• 

  Fig. 3 Assessing the commutability of reference materials (RMs) across five analytical systems for determining alpha-fetoprotein (AFP) concentrations, based on the International Federation of Clinical Chemistry and Laboratory Medicine [16] (IFCC) method. (A) Roche assay results – Abbott assay results. (B) Roche assay – Beckman assay. (C) Roche assay – Mindray assay. (D) Roche assay – Autolumo assay. (E) Abbott assay – Beckman assay. (F) Abbott assay – Mindray assay. (G) Abbott assay – Autolumo assay. (H) Beckman assay – Autolumo assay. (I) Beckman assay – Mindray assay. (J) Autolumo assay – Mindray assay. The bias of the logarithm ln (loge) of the concentrations measured with two measuring systems is shown in each case. The purple diamonds represent the six Beijing Center for Clinical Laboratories (BCCL) Can-RMs. The black circles represent the clinical samples (CSs). The error bars indicate the uncertainty of the difference in bias between each BCCL Can-RM and diluted WHO standard and the average bias for the CSs. The solid gray line is the bias-for-the-clinical sample (BCS) line, which represents the mean bias for all CSs. The red dashed lines (C lines) indicate the maximum allowable commutability-related bias (i.e., the commutability criterion [C]).

Reference

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