Alkaline Phosphatase (ALP)
Why this test?
Usually, this test is prescribed to detect diseases of the liver or bones. In addition, alkaline phosphatase increases in gallstone disease, when there is obstruction of the biliary tract due to stones in the bile ducts or tumors of the pancreas.
The test for alkaline phosphatase, as well as gamma-glutamyltransferase, is performed in order to diagnose diseases affecting the biliary tract: primary biliary cirrhosis and primary sclerosing cholangitis. Any conditions that are associated with bone growth or increased activity of bone cells increase the activity of alkaline phosphatase.
Therefore, the alkaline phosphatase test can be used to determine whether the tumor has spread beyond the primary focus - into the bones.
Repeated assignment of alkaline phosphatase is used to control the activity of diseases in which it is elevated, or to evaluate the effectiveness of treatment.
In what cases is it prescribed?
The alkaline phosphatase test can be part of standard diagnostic panels used in routine medical examinations and in the preparation of a patient for surgery. It is also commonly included in «liver tests» used to assess liver function.
This study is carried out when the patient complains of weakness, fatigue, loss of appetite, nausea, vomiting, abdominal pain (especially in the right hypochondrium), jaundice, darkening of urine or lightening of feces, itching of the skin. In addition, the analysis is prescribed for symptoms of bone damage: pain in the bones, their deformation, frequent fractures.
Alkaline phosphatase is an enzyme that is located in the cells of the liver and biliary tract and is a catalyst for certain biochemical reactions in these cells (it does not work in the bloodstream). When cells are destroyed, their contents enter the blood.
Normally, part of the cells are renewed, so a certain activity of alkaline phosphatase is detected in the blood. If many cells die, a significant increase in the level of this enzyme is observed.
The activity of alkaline phosphatase increases with obstructions to the outflow of bile, for example, stones in the bile ducts. This stagnation of bile is called cholestasis. In bones, alkaline phosphatase is formed in special cells - osteoblasts, which play an important role in the formation and renewal of bone tissue.
The higher the activity of osteoblasts, the higher the activity of alkaline phosphatase in the blood, therefore, in children and people who have suffered bone fractures, the activity of alkaline phosphatase is at a high level. Alkaline phosphatase is also found in intestinal and placental cells.