Does Low Total Creatine Kinase Rule Out Myocardial Infarction?
To the Editors: Serial creatine kinase and creatine kinase-MB measurements with clinical history findings, physical examination findings, and electrocardiographic (ECG) changes are the standards for diagnosing acute myocardial infarction (1, 2). Whether creatine kinase-MB measurements should be quantified when total creatine kinase activity never rises above the upper limit of the normal range is unclear (3, 4). We wondered whether there truly was an upper limit of the normal range for creatine kinase-MB measurements and whether percent relative index (creatine kinase-MB mass concentration/ total creatine kinase activity) might misdiagnose acute myocardial infarction when the total creatine kinase activity is normal.
