Use of the combination of myoglobin and CK-MB mass for the rapid diagnosis of acute myocardial infarction

Abstract

Early identification of patients presenting with myocardial infarction (MI) is necessary for rapid initiation of treatment. Currently, MI has been diagnosed using the combination of the history, electrocardiogram (ECG), and biochemical markers of myocardial necrosis. Unfortunately, all lack sufficient sensitivity and specificity to confidently identify most patients with MI in a timely enough fashion to influence early intervention. Development of newer immunochemical assays for CK-MB mass and myoglobin have allowed for earlier, more rapid diagnosis; however, each has important limitations. The diagnostic sensitivity of CK-MB mass, myoglobin, and the combination of both were analyzed at the time of presentation (0 hours) and again 4 hours later in 101 patients admitted from the emergency department (ED) with possible MI. Twenty patients were subsequently diagnosed as having MI. The sensitivity of the initial ECG was 60%, compared with the sensitivities of the initial myoglobin and CK-MB mass of 70% and 30%, respectively. By 4 hours the sensitivity of myoglobin had increased to 85% and CK-MB mass to 90%. The combination of the initial myoglobin and CK-MB mass had a sensitivity of 85%. Combining these two markers, using both the initial and 4-hour samples, raised the sensitivity to 100%, with a specificity of 100% and negative predictive value of 100%. When patients with diagnostic ECGs were excluded, the sensitivity of the combination at 0 hours was 80% with a specificity of 84%, while the use of the 0- and 4-hour markers had a sensitivity and specificity of 100% and 100%, respectively. We conclude that the combination of CK-MB mass and myoglobin can rapidly diagnose or exclude MI in as short as 4 hours after ED presentation, and accuracy is not different in patients without diagnostic ECGs. Application of this strategy could potentially lead to more rapid intervention in patients with MI, while also allowing early identification of lower risk patients.