Biochemistry Test

Test : Alkaline phosphatase


Indications : ALP test is ordered along with a group of other tests called 'liver profile' or 'liver panel'. It is also recommended when a person is suspected to have liver disease or bone disease.

In case of liver disease, damaged liver cells release high amounts of ALP into the blood stream. High alkaline phosphatase level could also indicate bone disease such as Paget’s disease or even conditions such as Vitamin D deficiency.

A person with liver disease may show signs of fatigue, loss of appetite, vomiting, nausea, abdominal swelling, abdominal pain or dark urine. Bone disease on the other hand may show pain in the bones or joints, increased frequency of fractures and deformed bones.

If after the test the cause of the elevated ALP levels is undetected a GGT test may be done. GGT is an enzyme whose levels are raised in liver disease but not in the case of bone disease.

Physiology : Alkaline phosphatase (ALP) is an enzyme that is present in all body tissues, notably in the liver, bones, intestine and the placenta.

It is a hydrolase enzyme that is responsible for removing the phosphate group through a process known as dephosphorylation. ALP has found tremendous use as a tool in molecular biology labs.

ALP levels also act as a diagnostic tool in identifying the presence of certain diseases. It is used to detect liver disease and also bone diseases such as Paget’s disease and bone cancer.

Normal Range : 44-77IU/l

Interpretation : The normal level of ALP ranges from 20 to 140 IU/L.

High ALP indicates the following-

• Liver damage - Alkaline phosphatase levels are high in the case of liver disease. Although conditions of the liver such as hepatitis cause increase in ALP levels it is much higher when a person has blocked bile ducts

• Bone disease - ALP levels are high in cases of bone disease such as Paget’s disease or, in cancers of the bone.

• Pregnancy can cause temporary increase in ALP levels

• Children and adults during their growth phase will have increased ALP levels

If there is difficulty in coming to a specific conclusion then the levels of GGT or 5'-nucleotidase is analyzed. If that too is increased, then the increased ALP is due to liver disease. If on the other hand the levels of calcium and phosphorus is increased then the increased ALP levels are due to bone disease.

If a person is successfully treated for Paget’s disease or bone cancer the ALP levels could decrease.

Low ALP level is seen in the following cases-

• Seen temporarily after blood transfusions / heart bypass surgery.
• Zinc deficiency
• Hypophosphatasia - A rare genetic disorder of bone metabolism

More Information

Some drugs may impact ALP levels. Oral contraceptives may bring about a decrease while anti-epileptics may increase ALP levels.

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