Diagnostic value of creatine phosphokinase (CPK) isoenzymes in the absence of elevated total CPK.

The value of creatine phosphokinase (CPK) isoenzymes, in the presence of normal total CPK, for assessing myocardial infarction is discussed. Forty-six patients in a coronary care unit were studied to ascertain the clinical usefulness of CPK isoenzymes for diagnosing myocardial infarction when the levels of total CPK were within normal range. The majority of patients studied had some cardiac abnormality on either ECG or x-ray examination. Approximately 50 percent of patients had chest pain, but only five of the 46 had a detectable CPK isoenzyme level on CPK electrophoresis. The results of this study suggest that CPK isoenzymes do not add anything of diagnostic value to the clinical picture if the total CPK is normal.