[Creatine kinase (CK) activity and its isoenzyme MB in the serum of randomly selected patients without acute coronary disease].

Elevations of creatine kinase (CK) are not specific for myocardial disease. However, enzyme release due to extracardial factors is not necessarily comparable in healthy and diseased persons. It is therefore questionable whether normal values obtained in a group of healthy or mildly ill subjects are also valid for severely ill patients. The activity pattern of CK and its isoenzyme MB was therefore examined in the serum of 100 consecutive patients attending the medical outpatient clinic and of 170 patients at the time of admission to the medical emergency ward. The clinical and laboratory findings and diagnoses for all patients are recorded. Acute coronary disease was excluded. Determination of CK was performed according to the method described by Oliver [21] and Preston [27], but the results were calculated for a reaction temperature of 30 degrees C and determination of CK-MB was in cue with the method described by Prellwitz [25]. 4% of the outpatients and 14% of the emergency patients had CK values of over 100 U/1. In the majority of the patients (19 of 28) with CK values of over 100 U/1, the history revealed that the elevated values could be attributed to skeletal muscle trauma. After these values had been excluded, the 95% percentile was 20-85 U/1 (outpatients) and 20-110 U/1 (emergency ward) for men and 15-90 U/1 (outpatients) and 20-75 U/1 (emergency ward) for women. Without this selection, the newly admitted male patients in particular would have presented considerably elevated values. Since an explanation was found for most of the elevating values, the adjusted figures show no major differences between outpatients and hospital patients. The limit for CK-MB activity indicative of cardiac origin is presumed to be between 4-10% of the total CK activity. However, individual variations are observed, since CK-MB activity in skeletal muscle in variable and atypical isoenzymes may interfere with CK-MB determination. In this study 14% of the patients admitted to the emergency ward with CK values of under 100 U/1 presented false positive CK-MB values of over 10% of the total CK activity. It is concluded that CK-MB determination using the antibody method does not afford reliable results when there is no elevation of total CK.