Myoglobin - serum

Definition

Serum myoglobin is a test that measures the amount of myoglobin in the blood.

Myoglobin is a protein in heart and skeletal muscles. When a muscle is exercised, it uses up available oxygen. Myoglobin has oxygen bound to it, thus providing an extra reserve of oxygen so that the muscle can maintain a high level of activity for a longer period of time.

When muscle is damaged, myoglobin is released into the bloodstream. Ultimately, it is excreted in the urine (see urine myoglobin).

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test

There is no special preparation.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Myoglobin levels may be obtained to confirm suspected muscle damage, including heart and skeletal muscle damage.

Normal Values

The normal range is 0 to 85 ng/ml (sometimes a normal result is reported as "negative").

Ng/ml = nanograms per milliliter

Normal value ranges may vary slightly among different laboratories.

What abnormal results mean

Greater-than-normal levels (a "positive" result) may indicate:

• Skeletal muscle ischemia (blood deficiency)
• Skeletal muscle trauma
• Skeletal muscle inflammation (myositis)
• Heart attack
• Muscular dystrophy
• Rhabdomyolysis
• Malignant hyperthermia (very rare)

What the risks are

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Special considerations

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

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Serum myoglobin