Serum Myoglobin Compared with Creatine Kinase in Patients with Acute Myocardial Infarction

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Abstract
In a retrospective study of 307 patients with suspected acute myocardial infarction (AMI) the diagnostic value of S‐myoglobin quantitation was compared with S‐creatine kinase (CK, EC 2.7.3.2). The results were compared with the final diagnoses, which were made according to the WHO criteria. A reference group of healthy blood donors and children hospitalized for removal of adenoids was investigated. Children (2–16 years) had significantly lower myoglobin levels (25±10 μg/l) than adults (19–65 years, 41±17 μg/l). In the children a positive correlation was found between age and S‐myoglobin concentration but not in adults. Women (34±17 μg/l) had lower S‐myoglobin concentration than men (47±15 μg/l). The difference in sensitivity for detection of AMI by S‐myoglobin or S‐CK analyses is not significant when the results from blood samples drawn on admission and on the following three mornings are compared, but myoglobin can be detected earlier in serum than CK after an AMI. If only the results from blood samples drawn on admission are compared, the S‐myoglobin analysis had a significantly higher sensitivity than the CK analysis. The S‐myoglobin analysis had a lower specificity than the CK analysis, and i.m. injections were found to be an important reason for false positive results. S‐myoglobin may be of value in the very early verification of AMI, but the frequent blood sampling and the low specificity are problematic. The simultaneous quantitation of S‐myoglobin and the heart specific CK isoenzyme fraction (MB) seems to be a good combination.