Characterisation and Evaluation of External Quality Assessment Scheme Serum

Abstract

This work reviews the procurement, specification and manufacture of serum for external quality assessment (EQA) and provides a checklist for scheme organisers. Guidance on the assessment of commutability and notes on the use of EQA materials to assess assay problems are provided. The importance of the appropriateness of materials in respect of scheme design and objectives, and the essential nature of a detailed specification prior to manufacture are emphasised.

Harmonization of Measurement Results of the Alcohol Biomarker Carbohydrate-Deficient Transferrin by Use of the Toolbox of Technical Procedures of the International Consortium for Harmonization of Clinical Laboratory Results

“…Linear regression results included the correlation coefficient (r), slope, and intercept calculated with nonparametric regression analysis according to Passing and Bablok (20 ). We assessed commutability with nonparametric regression analysis according to Passing and Bablok, Bland-Altman plots, and normalized residuals (21 ). We calculated analytical goals for imprecision with CV A Յ f CV I in which CV A was the analytical goal for imprecision, CV I the intraindividual CV, and f the factor for optimum (0.25), desirable (0.50), and minimum (0.75) CV A (22 ).…”

Interpretation of EQA results and EQA-based trouble shooting

“…Therefore, EQA materials should be tested for commutability and if evaluation of method differences is intended, it is mandatory. Additionally, the sample should be stable during the survey period, homogeneous, available in sufficient volume and have clinical relevant concentrations ( 10 , 11 ). Higher concentrations of components can be achieved by adding components (spiking) to pooled unaltered samples but this may induce non-commutability ( 12 , 13 ).…”

Commutable Calibrator with Value Assigned by the IFCC Reference Procedure to Harmonize Serum Lactate Dehydrogenase Activity Results Measured by 2 Different Methods

“…For each material, the residual was then computed and divided by the residual SD of patient sera to yield the normalized residual. We took the normalized residual of each material as the measure of its degree of commutability (21,28,29 ); normalized residuals outside the Ϯ3 interval were considered to indicate lack of commutability. For serum pools with abnormal isoenzyme pattern and for stabilized materials, we assessed commutability with the normal frozen pools in 2 pairs of methods including the reference procedure (either LP vs IFCC or PL vs IFCC) following the same experimental/statistical approach.…”