Myoglobin

Serum (gold top) tube

Serum (gold top) tube or Lithium Heparin Plasma (green top) tube

Daily upon receipt

0 - 101 ng/mL

Myoglobin is a globular heme protein with a molecular weight of approximately 17,800 daltons located in the cytoplasm of both cardiac and skeletal muscle cells. Myoglobin is an early marker of myocardial necrosis. It is released into the bloodstream in a temporal pattern. Clinical studies have demonstrated detectable levels of myoglobin as early as 1 hour after the onset of symptoms, and peak levels within 4 to 5 hours. Myoglobin is a very sensitive marker for acute myocardial injury, but due to its presence in both cardiac and skeletal muscle tissues, it is not a specific marker. Damage to either muscle type will result in an elevated myoglobin value. However, myoglobin is often used as a negative marker for acute myocardial infarction (AMI) since two consecutive results below the cutoff, along with other clinical information, could be used to rule out a diagnosis of AMI. Although myoglobin has the highest negative predictive value of any of the cardiac markers at very early time-points, the negative predictive value falls rapidly starting at approximately 6 hours. This fall in the negative predictive value is due to the rapid clearance of myoglobin from the blood after myocardial necrosis. Myoglobin levels may be elevated in many conditions, such as skeletal muscle trauma, skeletal muscle or neuromuscular disorders, cardiac bypass surgery, renal failure and strenuous exercise. Therefore, an elevated myoglobin result must be used in addition to other clinical information; e.g., other cardiac marker test results, ECG, symptoms, and clinical observations in order to aid in the diagnosis of AMI.