SERIAL MYOGLOBIN LEVELS FOR PATIENTS WITH POSSIBLE MYOCARDIAL-INFARCTION

Objectives: To determine the sensitivity and specificity of a new myog lobin assay for acute myocardial infarction (AMI), considering both th e total amount of serum myoglobin and its percentage change over 2 hou rs. Methods: A prospective, observational test performance study for t he recognition of AMI was done using serial myoglobin assays of 42 adm itted chest pain patients at a large, urban teaching hospital ED. Myog lobin testing was performed at presentation (time 0) and at 1 and 2 ho urs after arrival. A myoglobin level >100 mu g/L (ng/mL) or a change g reater than or equal to 50% from baseline (increase ol decrease) any t ime during the 2-hour period was considered positive. Patients and the ir physicians were blinded to the myoglobin results. The managing clin ician's final diagnosis of the presenting event was used as the diagno stic criterion standard. Results: The sensitivity of the myoglobin tec hnique for detection of AMI in the first hours in the ED was 13/14 (93 %; 95% CI: 66-100%). The 1 patient who had a false-negative test had e vidence of AMI on the ECG and an initially abnormal creatine kinase-MB (CK-MB assay. The specificity was 22/28 (79%; 59-92%). However, of th e 6 patients who had ''false-positive'' myoglobin tests, all had serio us illness: significant cardiac disease (n = 4), in-hospital death (n = 1), or deep venous thrombosis (n = 1). Conclusion: Myoglobin level d eterminations are sensitive tests to detect AMI during the first 2 hou rs of a patient's stay in the ED and may complement current clinical t ools.