Interferences between macro creatine kinase and creatine myocardial isoform(CK-MB) in patients with chest pain:a confusing laboratory results

Presented by Ehsan Jabari as a lecture in the heart disease section of the 6th Quality Improvement Congress 

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 Macro creatine kinase is an enzyme with higher molecular mass than the creatine kinase (CK) and indistinguishable from normal CK in quantitative total enzymatic assay. CK myocardial isoform (CK-MB) is marker commonly used for diagnosis of myocardial infraction (MI). The major clinical problem of macro CK lies in its potential for causing confusing laboratory results, particularly during investigation of MI possible because the enzyme pattern mimics that of a MI. This condition is the presence of CK-MB at a relatively high concentration, which sometimes greater than the normal total activity of CK. In this study we enrolled three hundred patients with suspicious symptoms of MI at the initial visit to the emergency ward of Alborz hospital, Karaj, Iran. Serum CK and CK-MB levels were measured and ratio of CK-MB to CK was calculated and then after macro CK was evaluated. Results showed that 2% and 41 % of all of the patients had a macro CK and MI situation respectively (CK: 229+ 54 IU/L, CK-MB : 276 + 65 IU/L, Ratio: 121 ± 1% and CK: 1063 186 IU/L, CK-MB: 155 32 IU/L, Ratio: 14.7 ± 1% respectively). We concluded for the prevention of interference of macro CK with CK-MB, the utilization of the troponin and myoglobin together CK-MB serum assay may clear up any diagnostic skeptical.