IFCC Working Group Recommendations for assessing commutability part 1: general experimental design

Abstract

Commutability is a property of a reference material that relates to the closeness of agreement between results for a reference material and results for clinical samples when measured by two or more measurement procedures. Commutability of reference materials used in a calibration traceability scheme is an essential property for them to be fit for purpose. Similarly, commutability of trueness controls or external quality assessment samples is essential when those materials are used to assess trueness of results for clinical samples from measurement procedures. This report is part one of a three part series describing how to assess commutability of reference materials. Part one defines commutability and addresses critical components of the experimental design for commutability assessment including: selection of individual clinical samples, use of pooled clinical samples, qualification of measurement procedures for inclusion, establishing criteria for the determination that a reference material is commutable, generalization of commutability conclusions to future measurements made with the measurement procedures included in the assessment, and information regarding commutability to be included in the certificate for a reference material. Parts two and three in the series present two different statistical approaches to commutability assessment that use fixed criteria related to the medical decisions made using the laboratory test results.