The levels of serum myoglobin in cardiac patients with elevated creatine kinase-MB and suspected acute myocardial infarction.

A monoclonal antibody enzyme immunoinhibition assay was used to quantitate serial serum myoglobin (Mb) levels in 121 patients who had > or = 5% creatine kinase-MB (CK-MB) and suspected acute myocardial infarction (AMI). Serum Mb levels higher than 0.16 micrograms/ml were considered abnormal. In 94% of these patients who were finally diagnosed with AMI, Mb levels were higher than 0.16 micrograms/ml, whereas all 30 normal control blood donors had lower Mb levels. Patients with anterior or inferior wall infarcts had higher Mb levels (> or = 0.64 micrograms/ml) than patients with lateral or subendocardial infarction. Only 68% (82/121) of patients evaluated by elevated CK-MB alone had a final diagnosis of AMI. In contrast, 94% (77/83) of patients who in addition showed elevated Mb had AMI. It is suggested that analysis of Mb levels allows a more accurate diagnosis of AMI in patients with elevated CK-MB than does reliance on CK-MB values alone.