Does this test have other names?

Bone turnover marker, tartrate-resistant acid phosphatase 5b, TRAP

What is this test?

This test looks for the chemical tartrate-resistant acid phosphatase (TRAP) in your blood. This test can also be done on bone marrow.

TRAP can appear in your blood if you have hairy cell leukemia. This is a kind of cancer that attacks your blood and bone marrow. With hairy cell leukemia, too many stem cells in your bone marrow develop into abnormal lymphocytes. Lymphocytes are a type of white blood cell. The abnormal cells build up in your marrow, leaving less room for healthy white blood cells. The abnormal lymphocytes also make TRAP.

TRAP can also show up in your bloodstream when bone is broken down in your body. This can happen if you have osteoporosis or cancer that has spread to the bones. Types of cancers that are likely to spread to the bones are cancers of the breast, prostate, kidneys, lung, pancreas, colon/rectum, stomach, thyroid, and ovaries.

Why do I need this test?

You may need this test if your healthcare provider thinks that you have hairy cell leukemia. Symptoms of hairy cell leukemia include:

• Fatigue 

• Weakness

• Fever or chills 

• Frequent infections

• Skin that bruises easily with no clear cause

• Shortness of breath during normal physical activity

• Unexplained weight loss

• Pain below your ribs

• Painless lumps in the neck, underarm, stomach and groin

You may also need this test if you have another type of cancer and your healthcare provider wants to find out if it has spread to your bones.

What other tests might I have along with this test?

You may also need other blood tests, scans, and a biopsy of your bone marrow.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

A negative result means that TRAP wasn't found in your blood. You don't have hairy cell leukemia. A positive result means that your bones are breaking down for some reason. If you have other tests that show you have hairy cell leukemia, it will help confirm the diagnosis.

If you have a positive result but not hairy cell leukemia, you may have other tests to confirm another cancer or another cause, such as osteoporosis.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect my test results?

No other factors affect your test results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.