[Acute myocardial infarction diagnosis. The value of serum myoglobin levels, compared with creatine kinase MB fraction].

PURPOSE

To compare the diagnostic performance of two traditional plasma markers of myocardial infarction (MI), creatine kinase (CK) and its MB fraction (CK-MB), with plasma myoglobin (Mgb) levels, for the diagnosis of MI.

METHODS

From September of 94 to February of 95, in an observational, prospective, and non-controlled fashion, 64 patients admitted to a cardiology emergency room (ER), with non-traumatic chest pain were studied. Patients presenting with more than 6 h after the onset of symptoms, muscular trauma, cardiopulmonary resuscitation and renal insufficiency were not included. Definitive MI diagnosis was established if the patient had at least two of the three classic MI findings: ischemic chest discomfort longer than 20 min, electrocardiogram with necrosis (Q waves) and elevated CK and CK-MB levels.

RESULTS

There were 18 patients with MI. The sensitivity for CK, CK-MB and Mgb were respectively 33%, 22% and 61%. The specificity was 85%, for CK, 95% for CK-MB and 97% for Mgb. The difference between Mgb and CK sensitivities was 28%, with a 95% confidence interval (CI) from -4% to 59%, the difference between Mgb and CK-MB sensitivities was 39%, (CI 9% to 69%). The difference between Mgb and CK specificities was 13%, (CI 12% to 14%) and the difference between Mgb and CK-MB specificities was 2%, (CI-5% to 9%).

CONCLUSION

In the studied population, Mgb was more sensitive than CK-MB for the diagnosis of MI with similar specificity and Mgb was more specific than CK for this diagnosis.