AACC Creatine Kinase MB (CK-MB) Standardization Material Used as Manufacturer’s Working Calibrator Is Unable to Harmonize CK-MB Results between Two Commercial Immunoassays

In recent years, meaningful efforts toward standardization of cardiac markers have been initiated by several organizations (1). The final objective of these standardization projects should be the promotion of result traceability by means of a reference measurement system by providing reference measurement procedures and reference materials (2). The progress in standardization of cardiac protein immunoassays has, however, been slow. As an interim solution, some authors have proposed assay harmonization by recalibrating various assays to give the same results (3). In this case, results may, however, be biased in terms of trueness. A major prerequisite for guaranteeing comparability of results among different methods is the availability of suitable reference materials, appropriately and thoroughly defined by a set of characteristics (2). Reference materials can be used for calibration of routine methods, but when reference materials are intended for direct value assignment to manufacturers’ calibrators, they should be extensively investigated for commutability (2). Commutability has been defined as the ability of a reference/control material for a given analyte to show interassay properties comparable to those of the same analyte in human serum (4). To directly calibrate manufacturers’ methods, matrix-based materials are desirable …