ALP - Alkaline Phosphatase (clinical analyzes)




Alkaline phosphatase (ALP) is an enzyme (substance that has the task of facilitating and accelerating a chemical reaction) present in various tissues of the body, in particular in the bones, liver, kidneys, intestines and placenta of women. pregnant. The highest concentration of ALP is found in bone and liver cells.

In the liver, alkaline phosphatase is present in the cells that line the bile ducts (small tubes that carry bile from the liver to the intestine and are necessary to facilitate the digestion of fats); in bones, however, it is produced by osteoblasts, cells involved in bone formation.

Depending on the type of tissue that produces them, there are different types of alkaline phosphatase that are called isoenzymes (enzymes of different shape and structure that facilitate and accelerate the same reaction).

The test to measure the concentration of alkaline phosphatase in the blood can be ordered by your doctor in the presence of signs and disorders (symptoms) attributable to liver or bone disease. The most common ailments include:

  • loss of appetite
  • nausea
  • He retched
  • weakness and fatigue
  • itch
  • abdominal bloating
  • abdominal pain
  • yellowing of the skin and whites of the eyes (jaundice)
  • dark urine
  • I made clear
  • bone pain
  • bone deformations
  • ease of fracture

The test consists in taking a small amount (sample) of blood from a vein in the arm. The sample is then subjected in the laboratory to the analysis of the alkaline phosphatase assay which allows to measure the concentration of the enzyme.

The test

The test

The examination (test) for checking the amount of alkaline phosphatase (ALP) present in the blood is very simple, has no contraindications and consists in taking a small amount of blood (sample) from the vein of an arm.

Although it is not necessary to fast, it is still recommended not to drink or eat before undergoing the test as food intake could alter the alkaline phosphatase concentration for a few hours, particularly the consumption of meat.

After the blood collection, you can immediately return to normal activities.

The use of certain drugs, such as oral contraceptives and anti-epileptics, can affect the results of the test, so if you are being treated with these drugs it is important to inform your doctor.

It is also good to know that pregnancy can affect the results of the examination, increasing the concentration of ALP, as well as temporary increases in the enzyme can also occur during the healing process of fractures. In children and adolescents the values ​​are more high because the bones are growing.

Alkaline phosphatase can also be elevated during menopause, a period in which the risk of osteoporosis increases.



Normally the concentration of alkaline phosphatase (ALP) in the blood varies according to the following ranges:

  • children up to 1 year, from 110 to 700 units per liter of blood (U / L)
  • children from 1 to 10 years, from 110 to 550 U / L
  • children from 10 to 15 years, from 130 and 700 U / L
  • adults, from 50 to 220 U / L

Reference values ​​may vary depending on the technique used by the laboratory.

If the doctor suspects liver disease, in addition to alkaline phosphatase, he usually also prescribes bilirubin and transaminase tests and evaluates the results obtained as a whole. If he suspects bone disease or if the ALP test results are normal, instead, it also prescribes tests to check for changes in phosphorus and calcium levels in the blood.

High levels of ALP in the blood may indicate liver damage or the presence of a disease that increases the activity of bone cells. They can therefore be associated with:

  • rheumatoid arthritis
  • lack of calcium
  • lack of vitamin D.
  • cirrhosis
  • excess fat
  • eclampsia
  • hepatitis
  • bone fracture in healing
  • pregnancy
  • Andexcessive functioning of the parathyroid glands (hyperparathyroidism)
  • leukemia
  • Paget's disease
  • bone metastases
  • mononucleosis
  • osteomalacia
  • biliary obstruction
  • pancreatitis
  • rickets
  • osteosarcoma
  • tliver mood
  • pancreatic cancer

Moderately elevated values ​​can result from other conditions, such as:

  • hyperparathyroidism
  • Hodgkin's lymphoma
  • Ulcerative colitis
  • lack of vitamin D.
  • congestive heart failure
  • bacterial infections

Low levels of ALP in the blood occur more rarely and can be caused by:

  • blood transfusions
  • heart bypass surgery
  • lack of zinc
  • malnutrition (especially a lack of protein)
  • celiac disease

The reading and evaluation of the results of the alkaline phosphatase (ALP) test must always be performed by the attending physician who, knowing the person's present and past state of health, will be able to interpret them.



Mayo Clinic. Liver function tests (English)

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