PTH-related protein

Definition

PTH-related protein is a blood test that measures the amount of PTH-related peptide (a protein molecule similar to PTH).

How the test is performed

Adult or child:

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, and a tourniquet is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to fill with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. The tourniquet is then removed to restore circulation. After blood has been collected the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:

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

No special preparation is necessary.

How the test will feel

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

Why the test is performed

This test is used to determine whether hypercalcemia (high blood calcium levels) is caused by an elevation of PTH-related protein. PTH-related protein is produced by some cancers, including lung, breast, leukemia, and lymphoma. High levels of PTH-related protein are the cause of high calcium levels in about two thirds of cancer patients.

Normal Values

No detectable (or minimal) PTH-like peptide is normal. Normal value ranges may vary slightly among different laboratories.

What abnormal results mean

Elevated levels of PTH-related protein in a patient with hypercalcemia generally indicates that cancer is the underlying cause.

What the risks are

• Excessive bleeding
• Fainting or feeling lightheaded
• 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.

Page Content:

PTHrp ; pthrp