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Tartrate-Resistant Acid Phosphatase

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. 

TRAP can appear in your blood if you have hairy cell leukemia, a kind of cancer that attacks your blood and bone marrow. It can also appear when bone is broken down in your body, as in the disease osteoporosis or in cancers that have spread to the bone.

If you have hairy cell leukemia, too many stem cells in your bone marrow develop into abnormal lymphocytes, a type of white blood cell. The abnormal cells build up in your marrow, leaving less room for health white blood cells. The abnormal lymphocytes make TRAP, which appears in your bloodstream.

In certain other types of cancer, you have a 50-50 chance that the cancer will spread to your bones. TRAP levels increase when this happens. Types of cancers that are likely to spread to the bones are breast, prostate, kidney, lung, pancreatic, colorectal, stomach, thyroid, and ovarian cancer.

Why do I need this test?

You may need this test if your doctor suspects that you have hairy cell leukemia. Symptoms of hairy cell leukemia include:

  • Fatigue or weakness

  • Fever or frequent infections

  • Skin that bruises easily

  • Shortness of breath

  • 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 doctor wants to find out if it has spread to your bones.

What other tests might I have along with this test?

Your doctor may also order other blood tests and a biopsy of your bone marrow.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning 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 your doctor has ordered 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, your doctor may order other tests to confirm another cancer or another cause, such as osteoporosis.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly 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 doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.