Myoglobin is found in both skeletal and cardiac muscle. Injury to skeletal or cardiac muscle results in increased serum levels shortly after injury.
Reference range in serum: serum levels are directly related to muscle mass:
• RIA: male: 19-92 µg/L; female: 12-76 µg/L
• INA: < 90µg/L
Course
Timing After AMI
earliest increase
2 - 3 hours
peak level
6 - 9 hours
return to normal
within 24-36 hours
Limitations:
• Myoglobin is present in both skeletal muscle and myocardium. Many conditions can result in elevated myoglobin levels, including uremia, trauma, seizures, myopathies, intramuscular injections, burns and exercise. Surgery increases myoglobin levels, so of little use in diagnosis of perioperative myocardial infarction.
• The increase in myoglobin can be missed if the patient delays presentation for medical care for 24 or more hours after injury.
Performance:
• While a positive myoglobin increase is of little utility, a normal myoglobin level is evidence against the diagnosis of myocardial injury.
• Sensitivity: 75-95%
• Specificity: 70%
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