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.
Why Is the Test Ordered?
Your doctor may order this test if they think you’re having a
heart attack. Most of the time, heart attacks are clinically 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 trauma. 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The serum myoglobin test has, for the most part, been replaced by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, troponin levels must also be measured, while also
obtaining a cardiac EKG.
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.
How Is the Test Administered?
The test is typically given in an emergency healthcare setting
when a person experiences symptoms of a heart attack. People 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
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, your
doctor will stick you with the needle 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. The elastic band is then released, and a
cotton ball or gauze is used to apply pressure to the site of entry.
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 eight to 12 hours. Myoglobin levels typically return to normal
within 24 hours. This allows the physician to compare changes in myoglobin
levels, if necessary.
Preparation for the Test
Since the test is often given in emergency situations, it’s
unlikely that you’ll be able to prepare for this.
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 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.
What Are the Risks of the Test?
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
What Do The Results Tell Us?
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 ng/mL. Normal
results will allow your doctor to rule out a heart attack
Abnormal (above 85) results can also be seen in:
- muscular inflammation (myositis)
- muscular dystrophy (hereditary disorders that
have muscles wasting and weakness)
- rhabdomyolysis (breakdown of muscle tissue from
prolonged coma, certain drugs, inflammation, prolonged seizures, and alcohol or