What is an Alkaline Phosphatase ALP test?
Written by Kimberly Vaughn, MD   
Sunday, 04 October 2009

This test measures an enzyme called alkaline phosphatase (ALP) in the blood. ALP occurs in all tissues, especially liver and bone.

Diseased or damaged tissues release ALP into the blood.
Who is a candidate for the test?

The alkaline phosphatase test is often used to help diagnose certain liver diseases and bone disorders.
How is the test performed?

To measure serum levels of ALP, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This restricts blood flow in the veins in the lower arm and enlarges them.

A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.