Myoglobin in myocardial infarction. Results in a coronary-care-unit population.

The purpose of this study was to define the performance characteristics of serum myoglobin determinations in the diagnosis of acute myocardial infarction (MI). Subjects of the study were 118 patients admitted consecutively to the coronary care unit. Daily measurements of serum myoglobin (by radioimmunoassay) were performed. For patients admitted within 24 hours of the onset of symptoms, a serum myoglobin level of 75 ng/ml had a diagnostic sensitivity of 91% and a specificity of 85%. In the same group of patients, the presence of the myocardial isoenzyme of creatine phosphokinase (CK-MB) showed a sensitivity of 94% and a specificity of 89%. Among the 32 patients with MI, the elevation of myoglobin preceded the appearance of CK-MB in 12 (38%), was concomitant with CK-MB appearance in 15 (47%), and followed CK-MB in none. Given the spectrum of patients in this coronary care unit, the addition of the myoglobin assay to the heart profile has increased its sensitivity for the diagnosis of MI. The assay materials are available in kit form, and the test can be performed in the routine radioimmunoassay laboratory. The results are available for reporting four to five hours after venipuncture.