Clinical and Laboratory Standards Institute EP30—Characterization and Qualification of Commutable Reference Materials for Laboratory Medicine provides guidance on characterizing and qualifying the fitness for use of commutable reference material (RM) as either a common calibrator or a trueness control for multiple measurement procedures. This guideline covers RM qualification requirements, characterization of homogeneity and stability, the assignment of quantity values, and determining RM value uncertainties. Three approaches for assessing commutability of RM are provided along with worked examples. Recommendations are made on how to report the results of the RM qualification process.

This guideline replaces CLSI EP30-A, published in 2010. Several changes were made in this edition, including: 

• Updating to align with the latest revision of ISO 17511 

• Changing content to align commutability assessment techniques with the latest revision of CLSI EP14 and with recommendations by the International Federation of Clinical Chemistry and Laboratory Medicine working group on commutability in metrological traceability 

• Updating content on characterization of stability to align with the latest revision of CLSI EP25

This guideline provides recommendations for the material characterization, assessment of commutability, and assignment of measurand concentration values to commutable RMs that are used at the higher levels of the calibration hierarchy. These RMs are created with the intent of promoting the generation of equivalent results for a measurand across multiple end-user MPs. Commutable RMs include: 

• Secondary certified reference materials (CRMs) 

• International conventional calibrators 

The commutable RMs covered in this guideline are all at position m.3 in the calibration hierarchies shown in Figures 1A, 1B, and 1C. The designations “m” for material and “p” for procedure are as used in ISO 17511 to designate sequential positions in calibration hierarchies. The m.3 designation is used for a commutable CRM or a commutable international conventional calibrator, which are the focus of this guideline. Similarly, a p.3 designation is used to describe the reference measurement procedure (RMP) used to assign the value of m.3, and a primary calibrator (m.2) designation can be used to describe the next higher-level calibration material in the calibration hierarchy, when applicable. 

Commutable RMs with a certified assigned value and associated uncertainty can be used as controls for trueness assessment of measuring systems. Commutable RMs without a certified assigned value can be used to assess equivalence of measuring system results, for example in an external quality assessment or proficiency testing program, but such applications are not in scope for this guideline. Also not in scope are MP manufacturer-specific working or end-user calibrators. 

This guideline does not apply to qualitative examinations whose purpose is to provide only nominal or ordinal results. In addition, laboratories should refer to CLSI EP25 for establishing and verifying the shelf life and in-use stability for reagent kits, calibrators, and control products.