[Macro creatine kinase. A cause of diagnostic problems in acute myocardial infarction]

Macro-creatine-kinase type 1 consists of complexes of CKBB isoenzyme and an immunoglobulin, most frequently IgG, while type 2 is probably aggregates of mitochondrial CK. The prevalences of type 1 and 2 have been found to be 0.9%-1.6% and 0.5%-2.9%, respectively, depending on the patient population investigated and the methods of analyses used. Problably a maximum of 1% of patients with suspected AMI, has macro-CK in concentrations causing diagnostic difficulties. In such patients, increased absolute and relative activities of CKB residual as measured by the immuno-inhibition method are found. In specific immunological methods for measuring CKMB concentrations in serum, macro-CK is not measured. However, it has been published, that these methods may underestimate the CKMB concentration in patients with free antibodies to CKB in the blood. In this department, we have evaluated a new analysis for measuring CKMB, without finding any evidence of such interference.