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IFCC working group recommendations for correction of bias caused by non-commutability of a certified reference material used in the calibration hierarchy of an end-user measurement procedure



Johanna Camara, W. Greg Miller, Jeffrey R. Budd, Neil Greenberg, Weykamp Cas, Harald Althaus, Heinz Schimmel, Mauro Panteghini, Vincent Delatour, Ferruccio Ceriotti, Thomas Keller, Douglas Hawkins, Robert Rej, Finlay MacKenzie, Elina van der Hagen, Hubert W. Vesper


Establishing metrological traceability to a matrix-based certified reference material (CRM) that has been validated to be commutable among a group of measurement procedures (MPs) is central to producing equivalent results for a measurand in clinical samples (CSs) irrespective of the clinical laboratory MPs used. When a CRM is not commutable with CSs, it is not suitable for use in a calibration hierarchy because the bias due to non-commutability will be propagated to the end-user CS results. In a commutability assessment, a conclusion that a CRM is commutable or non-commutable for use with a specific MP is made when the difference in bias between the CRM and CSs meets or does not meet a criterion for that MP when compared to other MPs. A conclusion regarding commutability or non-commutability requires that the magnitude of the difference in bias observed in the commutability assessment remains unchanged over time. This conclusion requires the CRM to be stable and no substantive changes in the MPs. These conditions must be periodically reverified. A commutable CRM should be used when available. If the available CRM is determined to be non- commutable for a specific MP, it is possible to use that CRM when an appropriately validated MP- specific correction for the non-commutability bias is included in the calibration hierarchy for the MP. We describe with examples how a MP-specific correction and its uncertainty can be developed and applied in a calibration hierarchy to achieve metrological traceability of results for CSs to the CRM.
Clinical Chemistry


Calibration, Certified Reference Material, Commutability, Harmonization, Standardization, Traceability
Created June 1, 2020