Tartrate resistant acid phosphatase (TRAP) is a test performed on blood cells or bone marrow (biopsy) to confirm a diagnosis of hairy cell leukemia. This test can also be done on blood plasma to look for signs of bone breakdown.

Type 5b acid phosphatase test; TRAP test

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

This test also can be done on a bone marrow biopsy.

No special preparation is needed for the blood test.

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.

Your doctor may order this test if you have signs of hairy cell leukemia. Hairy cell leukemia is a type of blood cancer in which TRAP levels are very high.

This test may also be done to monitor the activity of cancers that have spread to your bones. These cancers include multiple myeloma, and breast, lung, or prostate cancers. However, the test is not yet widely used for this purpose.

Review Date: 06/02/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)