Aim: /b> In this study, we evaluated the analytical performance and diagnostic adequacy of the activity and mass methods used for the measurement of CK-MB, a laboratory marker for the diagnosis of acute myocardial infarction (AMI). In addition, the differences between CK-MB results in serum and plasma samples were analyzed.

Materials and Methods: Recovery, interference, method comparison, and reproducibility studies were performed to determine the analytical performance of the methods. CK-MB results measured in serum and plasma samples were also compared.

Results: Within-run and between-run reproducibility results; For both methods, the pathological level was found to be lower than the desired % uncertainty value defined in the serum pools, while the activity was found to be higher in the normal level serum pool, lower than the desired % uncertainty value determined by the mass method. Recovery was 92.5% for the mass method and 92.9% for the activity method. The correlation coefficient (r) between the methods was 0.976. For CK-MB activity, both sensitivity and specificity values were 90%, and the area under the curve (AUC) was 0.939. For CK-MB mass, both sensitivity and specificity values were 95% and AUC was 0.980. There was no significant difference between plasma and serum values at the pathologic level for both methods. For normal levels, plasma samples measured by the CK-MB activity method were lower than serum samples (p=0.0039), while plasma samples were higher than serum samples by the mass method (p=0.0078).

Conclusion: The analytical performance and diagnostic adequacy of the mass and activity methods of CK-MB measurement were found to be compatible with each other. In serum and plasma samples, the results measured by both methods were found to be compatible with each other at pathologic levels of CK-MB, but different from each other at normal levels.