Elevation of creatine kinase BB CK in hospitalized patients. Importance of distinguishing BB CK from MB CK

Nine hundred and forty patients (1023 samples) were analyzed by cellulose acetate electrophoresis for creating kinase MB (MB CK) in the routine clinical chemistry laboratory during screening for acute myocardial infarction. Thirty patients showed the presence of BB CK and the associated disease states were identified. Rigid criteria were applied to demonstrate the activity observed was genuinely BB CK. It is noted and demonstrated that careful attention must be paid to the methodology used to distinguish CK isoenzymes, because some assays do not differentiate between BB CK and MB CK. It was shown by us that the false positive rate for MB CK could be as great as 19 percent in laboratories using non-discriminant assays for MB CK. Thus, the laboratory must know the limitations of the assays employed to avoid potential errors in MB CK results that could be misused as biochemical evidence of a myocardial infarction.