What is a serum myoglobin test?
A serum myoglobin test is used to measure the level of myoglobin in your blood.
Myoglobin is a protein that’s typically found in heart and skeletal muscle tissues. The only time that myoglobin is found in the bloodstream is when injury to a muscle has occurred. In particular, injury to the heart muscle results in the release of myoglobin. When detected through a blood test, the presence of myoglobin is clinically significant.
Your doctor may order this test if they think you’re having a heart attack. Most of the time, heart attacks are obvious, based on symptoms and family history. There are times, however, when a heart attack is not outwardly clear. Serum myoglobin levels may be elevated in cases of inflammatory and degenerative muscle diseases and following muscle injury. This can help your healthcare provider make a diagnosis.
The serum myoglobin test has, for the most part, been replaced by the serum troponin level test. The troponin level test can provide a positive diagnosis of a heart attack. This is because troponin levels are more specific to heart damage than myoglobin levels. Troponin levels will also stay higher than myoglobin levels for longer time periods, when there’s a heart attack.
Serum myoglobin is still used in some cases, though. The test is commonly ordered alongside other tests for cardiac biomarkers. Cardiac biomarkers are substances released into the bloodstream when damage to the heart takes place. A serum myoglobin test may also be taken with tests measuring troponin, creatine kinase (CK), and creatine kinase-MB (CK-MB).
Negative results can be used to rule out a heart attack. Positive results don’t confirm that a heart attack has happened, though. In order to definitively diagnose a heart attack, a doctor will look at your troponin levels and have you undergo an electrocardiogram (EKG). An EKG is a test that measures the electrical activity of your heart.
If you’ve been diagnosed with a heart attack, your doctor may still order a serum myoglobin test. Once damage to the heart muscle has been confirmed, values obtained from the test can help your doctor estimate the amount of muscle damage that has occurred. A serum myoglobin test may also be ordered if you have symptoms of kidney disease or kidney failure.
The test is typically given in an emergency healthcare setting when a person experiences symptoms of a heart attack. Those admitted to the emergency room with symptoms of a heart attack will likely have the test administered immediately.
The test requires a blood sample. First, your healthcare provider will use an antiseptic to clean the area for the needlestick. Common locations are the inside of the elbow and the back of the hand. Then, they will insert the needle into a vein and begin to draw blood.
An elastic band is tied around the arm in order to slow the flow of blood. The blood is drawn into a tube that is connected to the needle and sent to the laboratory for analysis. Your healthcare provider will then release the elastic band and apply pressure to the site of the blood draw using a cotton ball or gauze.
This test should be performed every two to three hours for up to 12 hours following admission. Serum myoglobin levels begin to increase within two to three hours following a heart attack. These levels reach their highest values within 8 to 12 hours. Myoglobin levels typically return to normal within 24 hours. This allows your healthcare provider to compare changes in myoglobin levels, if necessary.
Because the test is often given in emergency situations, it’s unlikely that you’ll be able to prepare for it.
If possible, you should tell your healthcare provider about recent health issues or testing you may have undergone.
People who have recently experienced an angina attack may have increased myoglobin levels. Additionally, people who have undergone cardioversion — a procedure for restoring heart rhythm back to normal — may also have increased levels of the protein. People who have kidney disease should report this medical issue, because kidney disease will result in high levels of myoglobin in the bloodstream.
You should also inform healthcare providers about any drug and alcohol use. Heavy alcohol consumption and the use of certain drugs can cause muscle injury, which also increases myoglobin levels.
The serum myoglobin test has minimal risk. The risks of this test are common to all blood tests and include the following:
- difficulty obtaining a sample, resulting in the need for multiple needlesticks
- excessive bleeding from the needle puncture site
- fainting as a result of blood loss
- the accumulation of blood under the skin, known as a hematoma
- development of infection where the skin has been broken by the needle
The range of normal results for the serum myoglobin test will vary slightly based on the laboratory completing the analysis. In most instances, the normal (or negative) range for the serum myoglobin test is 0 to 85 nanogram per milliliter (ng/mL). Normal results will allow your doctor to rule out a heart attack.
Abnormal (above 85 ng/mL) results can also be seen in:
- muscular inflammation (myositis)
- muscular dystrophy (hereditary disorders that cause muscle wasting and weakness)
- rhabdomyolysis (breakdown of muscle tissue from prolonged coma, certain drugs, inflammation, prolonged seizures, and alcohol or cocaine use)
Your doctor may suggest additional tests to reach a diagnosis if your results are outside of the normal range.