WHAT IS MYOGLOBIN TEST?
Myoglobin is a heme-containing, oxygen-binding protein similar to haemoglobin that is exclusive to striated and nonstriated skeletal or cardiac muscle. It functions as short-term oxygen storage, carrying the muscle from one contraction to the next. It is released into the interstitial fluid with elevated serum levels detected as early as 30-60 minutes after a myocardial infarct or damage to any muscle tissue. Serum myoglobin is generally detected earlier than traditional cardiac enzymes (total creatinine kinase [CK] or isoenzyme creatinine kinase–MB [CK-MB]). Because myoglobin is contained in both skeletal and cardiac muscle, it is not used alone to diagnose myocardial infarction. Tests used in combination with myoglobin for this purpose include troponin and CK-MB, with or without carbonic anhydrase III (a marker for skeletal muscle damage). Serum myoglobin may lack specificity in the diagnosis of myocardial infarct. Elevated levels are also observed after angina, chest trauma, cocaine use, electrical accidents, exercise, intramuscular injection, muscular injury of any type, and renal failure. Within 8 hours of symptoms, myoglobin specificity is 97.9% for acute MI, as opposed to CK-MB, which has 100% specificity.