Alkaline phosphatase test (ALP)
The Alkaline Phosphatase (ALP) test is a blood test that measures the levels of alkaline phosphatase, an enzyme involved in digestion and bone development. ALP is present in various tissues throughout the body, with higher concentrations found in the liver, bones, bile ducts, kidneys, placenta, leukocytes, and intestines. This test is often part of a broader chemistry or liver panel and is used to identify potential liver or bone diseases, including cancer. Elevated ALP levels can indicate issues in these areas, although the test does not specify the source of the increased enzyme.
Preparation for the test may require fasting for six to twelve hours, and the procedure involves drawing blood from a vein or, in children, from a capillary. While generally safe, there are minor risks associated with blood collection, such as bruising or fainting. Results can vary based on factors like age, sex, and the specific analyzer used, with normal ranges determined by individual laboratories. If elevated ALP levels are detected, further tests may be needed to pinpoint the specific cause, including additional blood tests or imaging studies. Following treatment for any diagnosed condition, monitoring ALP levels can help assess the effectiveness of the intervention.
On this Page
Alkaline phosphatase test (ALP)
ALSO KNOWN AS: ALKP, alk phos, alkaline phosphatase total
DEFINITION: Alkaline phosphatase (ALP) is an enzyme that helps in the process of digestion and bone development. All tissues contain ALP. Higher concentrations are found in the liver, bone, bile ducts, kidney, placenta, leukocytes, and intestines. Various processes within the tissues release ALP into the blood. By measuring ALP blood levels, doctors can determine the presence of liver and bone disease, including cancer. There is also an indirect link between bone ALP levels and hearing loss. ALP levels are determined by testing serum or plasma on an automated chemistry analyzer.
Cancers diagnosed: Cancers of the bone, renal cells, liver, gallbladder, and bile ducts
Why performed: The test is done as a part of a chemistry or liver panel to detect liver or bone disease. Once a diagnosis has been made and treatment started, the test may be done to determine if treatment is effective or if the disease has progressed or returned.
Patient preparation: The patient may be asked not to eat or drink or take certain medications for six to twelve hours prior to the test.
Steps of the procedure: A small sample of blood is collected from a vein and placed in a tube. In children, blood may be obtained from a capillary in the heel or finger.
After the procedure: A small gauze or cotton ball is applied at the site of needle insertion. The patient is asked to apply pressure. The person collecting the blood observes the site for bleeding and may apply a bandage. The bandage may usually be removed in thirty to sixty minutes.
Risks: Risks from the procedure include bleeding, bruising, hematoma (bleeding under the skin), fainting, light-headedness, or the need for multiple needle sticks to obtain a sample.
Results: Normal ALP levels vary by the patient’s sex and age and by the analyzer used. Each laboratory establishes a set of normal ranges based on this information. The physician receives a report of the test results with the normal values established by the testing laboratory.
Elevated levels indicate the possibility of liver or bone disease, including the presence of a tumor. The test does not distinguish from which tissue the increased amount of alkaline phosphatase comes. The physician may order other blood tests, including an alkaline phosphatase isoenzyme test that determines if the increased ALP comes from bone, liver, or intestine. Other procedures such as X-rays, scans, or other imaging may also be ordered. Following cancer treatment, ALP levels are expected to decrease. If levels remain high or increase, then some cancer may remain or has returned.
Bibliography
Chernecky, Cynthia C., and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures. 6th ed. St. Louis: Elsevier, 2013. Print.
Dugdale, David C., III. "ALP - Blood Test." MedlinePlus. US Natl. Lib. of Medicine, 29 Apr. 2013. Web. 9 Oct. 2014.
Flamm, Steven L, and Norman Gitlin, eds. Approach to Consultations for Patients with Liver Disease. Philadelphia: Saunders, 2012. Print.
Goldman, Lee, and Andrew I. Schafer. Goldman's Cecil Medicine. 24th ed. Philadelphia: Elsevier, 2012. Print.
Lim, Z.W., and W.L. Chen. "Exploring the Association of Bone Alkaline Phosphatases and Hearing Loss." Scientific Reports 10, Article 4006 (2020). doi.org/10.1038/s41598-020-60979-3.
Pagana, Kathleen Deska, Timothy J. Pagana, and Theresa Noel Pagana. Mosby's Diagnostic and Laboratory Test Reference. 12th ed. St. Louis: Elsevier, 2014. Print.