Creatine Kinase-MB measurement using Immunoinhibition methodology. How much is the interference?

Abstract

Introduction: Creatine kinase-MB (CK-MB) is considered as sensitive and specific indicator for myocardial infarction. Various methods are available for CK-MB measurement but are associated with inherent shortcomings. The routinely used Immunoinhibition method is evaluated for the various interferents and their impact on the estimated CK-MB value.
Materials and Methods: The CK-MB values were analyzed for 500 patient samples whose total CK values were within the normal reference interval. Immunoinhibition method (INH) & N-Acetylcysteine (NAC) methods were used for CK-MB and total CK estimation respectively.
Results: The observed mean S.D. for CK was 90.15 48.9 U/L and for CK-MB was 33.29 20.47 U/L. The box and whisker plots were used to represent the data of CK & CK-MB. The CK-MB levels were observed to exceed the total CK under certain circumstances owing to interferents. The CK-MB values were observed to exceed the total CK in 8.6% of the cases.
Conclusion: The utility of CK-MB has ever been questioned. It has been categorized as over-used test. The conventional immunoassay methodology for CK-MB measurement is not free from interferences, awareness about these is important while interpreting the results so as to exclude method related artifactual values.