The early diagnosis of acute myocardial infarction

Latex agglutination for serum myoglobin (Rapitex) was compared with the initial ECG for the early diagnosis of acute myocardial infarction. Forty patients suspected of myocardial infarction were prospectively evaluated by initial electrocardiogram and Rapitex serum myoglobin. The initial ECG was categorised into one of three groups: Group 1 had ST segment elevation of at least 1 mm in a limb lead or 2 mm in a precordial lead (with or without Q waves); Group 2 had abnormalities other than those seen in Group 1; and Group 3 had no particular abnormalities present that is, a normal ECG. Myocardial infarction was confirmed by a rise in creatine kinase to greater than or equal to twice the upper limit of normal for our laboratory range and with a CKMB fraction of greater than 6%. Nineteen of 40 patients sustained myocardial infarction; nine ECG group 1, six ECG group 2, and four ECG group 3. Eleven of the 19 patients with myocardial infarction had positive serum myoglobin agglutination. The initial ECG was the most predictive of a subsequent rise in CK (p = 0.003), while Rapitex serum myoglobin determination was the least predictive (p = 0.8517). We conclude that the Rapitex serum myoglobin test offers little diagnostic or economic advantage over the initial electrocardiogram.