Alkaline phosphatase examination: what it is, what it is for and results

The alkaline phosphatase test is generally used to investigate diseases in the liver or bones, when signs and symptoms are present such as pain in the abdomen, dark urine, jaundice or bone deformities and pain, for example. It can also be performed as a routine exam, along with other exams, in order to assess liver health.

Alkaline phosphatase is an enzyme that is present in several tissues of the body, being in greater quantity in the cells of the bile ducts, which are channels that lead the bile from the inside of the liver to the intestine, making the digestion of fats, and in the bones being produced by the cells involved in its formation and maintenance.

Although in lower amounts, alkaline phosphatase is also present in the placenta, kidney and intestine and may therefore be elevated in pregnancy or in cases of renal failure.

What is it for

The alkaline phosphatase test is used to investigate liver or bone disorders and its result can identify:

1. High alkaline phosphatase

Alkaline phosphatase can be elevated when there are liver problems such as:

• Obstruction of bile flow, caused by gallstones or cancer, which block the channels that lead bile to the intestine;

  Hepatitis, which is an inflammation in the liver that can be caused by bacteria, viruses or toxic products;

  Cirrhosis, which is a disease that leads to the destruction of the liver;

  Consumption of fatty foods;

  Renal insufficiency.

In addition, this enzyme may be very high in situations where there is an increase in bone formation activity, such as in some types of bone cancer or in people with Paget's disease, which is a disease that is characterized by the abnormal growth of certain bone parts. Learn more about Paget's disease.

Slight changes can also occur during periods of fracture healing, pregnancy, AIDS, intestinal infections, hyperthyroidism, Hodgkin's lymphoma, or even after a high-fat meal.

2. Low alkaline phosphatase

Alkaline phosphatase levels are rarely low, however this enzyme may be decreased in the following situations:

• Hypophosphatasia, which is a genetic disease that causes deformations and fractures in the bones;

  Malnutrition;

  Magnesium deficiency;

  Hypothyroidism;

  Severe diarrhea;

  Severe anemia.

In addition, some remedies such as the birth control pill and remedies for hormone replacement therapy used in menopause, may also cause a slight decrease in alkaline phosphatase levels.

When to take the exam

The examination of alkaline phosphatase should be done when signs and symptoms of liver disorders such as enlarged abdomen, pain in the right side of the abdomen, jaundice, dark urine, light stools and generalized itching are present.

In addition, this test is also indicated for people who have signs and symptoms at the level of bones such as generalized bone pain, bone deformities or who have suffered fractures.

How the exam is done

The test can be performed in a laboratory, where a healthcare professional takes about 5 ml of a blood sample from a vein in the arm, which is placed in a closed container, to be analyzed.

Reference values

Reference values ​​for the alkaline phosphatase test vary with age, due to growth:

Children and adolescents:

• <2 years: 85 - 235 U / L2 at 8 years: 65 - 210 U / L9 at 15 years: 60 - 300 U / L16 at 21 years: 30 - 200 U / L

Adults:

• 46 to 120 U / L

In pregnancy, blood values ​​of alkaline phosphatase may be slightly altered, due to the growth of the baby and because this enzyme is also present in the placenta.

Along with this examination, the examination of other enzymes found in the liver, such as alanine aminotransferase, aspartate aminotransferase, gamma glutamyl transpeptidase and bilirubins, imaging tests or even a liver biopsy can also be performed. See how these exams are done.