What is alkaline phosphatase?

Alkaline phosphatase (ALP) is an enzyme that catalyzes the cleavage of orthophosphate from orthophosphoric monoesters under alkaline conditions. There are differing forms of the enzyme that occur in normal and malignant tissues. The alkaline phosphatase enzyme is found in many tissues and organs, especially in the liver, bones, intestines, kidneys, and the placenta. The alkaline phosphatase enzyme has optimum function at pH levels of 8.6. Like all enzymes in the body, alkaline phosphatase is need in small amounts to trigger specific chemical reactions within the body. Abnormally high serum levels of alkaline phosphatase may indicate bone disease, liver disease, or that there is a bile duct obstruction. Alkaline phosphatase of the liver is produced by the cells lining the small bile ducts or ductoles in the liver. Each tissue, such as the liver, bone, placenta, and intestine produce a slightly different alkaline phosphatase. These variations are known as isoenzymes. Different types of alkaline phosphatase produced are also called isoenzymes.

Growing bones need alkaline phosphatase for proper formation. Any condition of bone growth will therefore cause alkaline phosphatase levels in the blood to rise. This condition is completely normal, such as that of childhood growth spurt or the healing of a broken bone, however sometimes the rise of alkaline phosphatase levels in the body may be due to diseases such as bone cancer, Paget’s disease, or that of rickets.


Why measure the level of alkaline phosphatase?

Alkaline phosphatase is measure to verify the correct functioning of the liver in a patient. In a healthy liver, fluid containing alkaline phosphatase and other substances is continually drained away through the bile duct. However in a diseases liver, the bile duct is often blocked, and hence this keeps fluid within the liver. Alkaline phosphatase and eventually escapes into the bloodstream. If the liver disease is that of an obstructive nature such as cholestatic, it then involves the biliary drainage system, and the alkaline phosphatase will be the first and foremost enzyme elevation. However if the disease is primarily that of the liver cells or hepatocytes, then the level of aminotransferases will rise greatly. Hence why these enzymes are so useful in the processes of distinguishing the type of liver disease, whether it is cholestatic or that of hepatocellular.  The level of alkaline phosphatase present within a person’s body or blood depend on their age and sex, and may also vary depending on the type of laboratory test used.


Standard of preparation

Sampling is usually done in the morning in the hospital. There are no special preparations needed for this test. The doctor will advise and recommend if you need to be fasting prior to the blood examination. You should inform your doctor of any medication you are taking prior to the exam, as some medical treatments may interfere with the blood results.


Is the examination painful or dangerous?

The examination is neither painful nor dangerous. The patient may feel a tingling sensation with the entrance of the needle in the arm when blood is being extracted for examination.


How is the exam performed?

The exam consists of a simple blood sample test.