- Red, tiger, or green top tube
- 5-7 mL of venous blood
Additional information
- Avoid vigorous exercise prior to the test
- Handle sample gently to prevent hemolysis
- Send sample to lab immediately
- Collection of 2 or 3 samples taken 1-2 hrs apart is preferred for evaluation of myocardial infarction
- Reject lipemic samples
- The myoglobin test is a quantitative analysis of myoglobin in the blood
- Myoglobin is a monomeric heme protein found in skeletal and cardiac muscles as an intracellular storage site for oxygen
- Oxymyoglobin releases its bound oxygen only at extremely low oxygen tension
- Myoglobin is usually released in the bloodstream after muscle damage due to ischemia, trauma, or inflammation
- As myoglobin is not tightly bound to any protein, it is rapidly excreted in the urine
- The clinical utility of the serum myoglobin assay includes:
- Detection and estimation of damage or necrosis to skeletal muscle
- For early detection of myocardial infarction along with other cardiac biomarkers (CPK-MB fraction, Troponin)
- Serial measurement of myoglobin is useful to calculate the total myoglobin release and estimate myocardial infarct size
- To aid in the diagnosis of rhabdomyolysis
- To aid in predicting a flare-up of polymyositis
- Myoglobin is one of the earliest biomarkers to elevate in myocardial infarction
- Myoglobin is detectable 1-3 hours after the onset of myocardial ischemia, and reaches peak levels at 6-10 hrs, followed by rapid fall in the levels
- The cumulative release of myoglobin correlates with infarct size
- Myoglobin though sensitive, is relatively non-specific to cardiac muscle due to its wide distribution, and hence it is usually used in conjunction with other cardiac biomarkers
- Myoglobin is more sensitive than creatine phosphokinase (CPK), and has an excellent negative predictive value for ruling out acute myocardial infarction in patients with typical or atypical symptoms
- Elevated myoglobin along with a five fold increase in creatine phosphokinase (CPK-MM), in the absence of cardiac or brain injury, is a sensitive diagnostic indicator for rhabdomyolysis
- Rhabdomyolysis may clinically present as:
- Local features
- Muscle pain
- Tenderness
- Swelling
- Bruising
- Weakness
- Systemic features
- Tea-colored urine
- Fever
- Malaise
- Nausea
- Emesis
- Confusion
- Agitation
- Delirium
- Anuria
Additional information
- Factors interfering with the test results include:
- Hemolyzed or lipemic sample
- Radioactive scan performed within 1 wk of test
- Intramuscular (IM) injections can cause false positive levels
- Recent angina, cardioversion, or improper timing of test
- Related laboratory tests include
- Apolipoprotein A and B
- Aspartate aminotransferase
- Atrial natriuretic peptide
- Blood gases
- B-type natriuretic peptide
- Calcium (blood and)
- Cholesterol (total,, and)
- C-reactive protein
- Creatine kinase and isoenzymes
- Glucose
- Homocysteine
- Ketones
- Lactate dehydrogenase and isoenzymes
- Lipoprotein electrophoresis
- Magnesium
- Pericardial fluid
- Potassium
- Troponin
- Urine myoglobin
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
| Conv. units (ng/mL) | SI units (µg/L) |
|---|---|
| <90 | <90 |
Conditions associated with elevated myoglobin levels (myoglobinemia / hypermyoglobinemia) include:
- Cardiac conditions
- Acute myocardial infarction
- Angina without infarction
- Skeletal muscle conditions
- Acute alcoholism with delirium tremens
- Idiopathic inflammatory myopathy
- Polymyositis
- Dermatomysitis
- Inclusion body myositis
- Intramuscular injections
- Myositis
- Progressive muscular dystrophy
- Rhabdomyolysis
- Trauma such as crush injury, surgical procedures, electric shock, burns, near drowning, prolonged immobilization
- After excessive muscular activity such as exercise, status epilepticus, status asthmaticus, dystonia, acute psychosis
- Envoirmental such as hypothermia (with prolonged shivering), malignant hyperthermia
- Metabolic such as hypokalemia, hyponatremia, hypernatremia, hypophosphatemia, diabetic ketoacidosis, hyperthyroidism etc.
- Myopathies, including systemic lupus erythematosus (SLE)
- Certain viral, bacterial and fungal infections
- Toxic mediated (substance abuse) such as cocaine, heroin, methanol, ethylene glycol, amphetamine, ectasy, lysergic acid diethylamide (LSD) etc
- Other toxins such as Malayan sea snake toxin, carbon monoxide, toluene, black widow spider etc
- Drugs:
- Aminocaproic acid
- Amphoterecin B
- Antihistamines
- Corticosteroids
- Fluvastatin & possibly other statins
- Neuroleptics
- Quinine
- Salicylates
- Theophylline
- Tricyclic antidepressants
- Thrombolytic therapy
- Renal insufficiency or renal failure
Conditions associated with decreased myoglobin levels include:
- Circulating antibodies to myoglobin, as in polymyositis patients
- Myasthenia gravis
- Rheumatoid arthritis
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