Health Encyclopedia

Leukocyte alkaline phosphatase

Definition

Leukocyte alkaline phosphatase is a test that tells how much alkaline phosphatase (ALP) you have inside your white blood cells. Leukocyte means white blood cell.

Alternative Names

ALP test - leukocytes

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, and an elastic band is placed around the upper arm. This causes veins below the band to fill 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 blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants and 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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

A laboratory specialist seperates the white blood cells from the rest of the blood sample and watches to see if any substances attach to certain colored dyes. Substances that contain phospate, such as ALP, attach to certain colored dyes.

How to prepare for the test

You should not eat or drink for 6 hours before the test.

Certain medicines can affect the test results. Your health care provider may tell you to stop taking such medications. These medications include:

Allopurinol
Androgens
Anti-inflammatory medicines
Birth control pills
Certain antibiotics
Certain arthritis drugs
Certain diabetes drugs (taken by mouth)
Chlorpromazine
Cortisone
Methyldopa
Narcotics
Propranolol
Tranquilizers
Tricyclic antidepressants

NEVER stop taking any medicine without first talking to your doctor.

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

ALP is found in different forms throughout the body. This test is done to confirm a number of different medical conditions, including certain types of anemia and leukemia.

Your doctor may also order this test if you have an increase in platelet levels in the blood.

Normal Values

A staining score of 20 to 100 (out of a maximum of 400) is considered normal.

What abnormal results mean

Higher-than-normal results may be due to:

Leukemoid (leukemia-like) reaction
Myelofibrosis
Polycythemia vera

Lower-than-normal results may be due to:

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.

References

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:803-804.

Goldman L, Ausiello D. Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders; 2004:987-988.

Review Date:3/8/2007
Reviewed By:Mark Levin, MD, Hematologist and Oncologist, Newark, NJ. Review provided by VeriMed Healthcare Network.

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