Value of additional two-hour myoglobin for the diagnosis of myocardial infarction in the emergency department

Myoglobin has been described as an early marker of myocardial injury. It in creases within 1 to 3 hours of myocardial injury, and falls back to normal early after the event. Few data suggest that myoglobin can be used to triag e patients with chest pain. To assess the diagnostic utility of second myog lobin levels drawn within 2 to 3 hours after presentation to the emergency department for detecting myocardial infarction, we prospectively collected myoglobin levels in 368 patients aged greater than or equal to 30 years who were admitted with chest pain. Myoglobin levels were measured at admission and 2 to 3 hours later. Sensitivity and specificity for detecting acute my ocardial infarction for a twofold increase in myoglobin level from baseline were 39% and 98%, respectively. The early diagnostic performance of myoglo bin at admission, the second level drawn 2 to 3 hours later, and creatine k inase-MB mass drawn at admission were similar (receiver-operating character istic curves 0.80, 0.86, and 0.85), The diagnostic performance of each of t hese markers was significantly superior to the absolute change from baselin e to second myoglobin (receiver-operating characteristic curve 0.77). In pa tients who presented within 4 hours of symptom onset, myoglobin drawn 2 to 3 hours later had the highest yield for detecting myocardial infarction, Th ese results suggest that serial myoglobin measurement aiming to detect chan ges over time is not superior to single marker determinations. Myoglobin me asured in 2 to 3 hours from admission may be helpful in triaging patients w ho present within 4 hours from onset of symptoms. (C) 1999 by Excerpta Medi co, Inc.