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Ency. home > Test > A > ALP

ALP   

Overview | Risks | Results

Alternative names:

Alkaline phosphatase

Definition:

A test that measures the amount of the enzyme ALP (alkaline phosphatase) in serum.

How the Test is Performed

Blood is drawn from a vein (venipuncture) or a capillary sample is obtained from a heel, finger, toe, or earlobe. The laboratory centrifuges the blood to separate the serum from the cells. The ALP test is done on the serum.

How to Prepare for the Test

Fast for 6 hours.

Your health care provider may advise you to discontinue drugs that may affect the test, such as:

  • antibiotics
  • narcotics
  • methyldopa
  • propranolol
  • cortisone
  • allopurinol
  • tricyclic antidepressants
  • chlorpromazine
  • oral contraceptives (birth control pills)
  • anti-inflammatory analgesics
  • androgens
  • tranquilizers
  • some antiarthritic drugs
  • oral antidiabetic drugs.

Why the Test is Performed

Alkaline phosphatase is an enzyme in all tissues. Tissues with particularly high concentrations include liver, bile ducts, placenta and bone. Since damaged or diseased tissue releases enzymes into the blood, serum ALP measurements can be abnormal in many conditions, including bone disease and liver disease. However, serum ALP is also increased in some normal circumstances (for example, during normal bone growth) or in response to a variety of drugs.

There are multiple varieties of ALP, called isoenzymes, which have slightly different structures. Different types of isoenzymes are in different tissues (for example, liver and bone ALP isoenzymes have different structures) and can be quantified separately in the laboratory. To differentiate the location of damaged or diseased tissue in the body, ALP isoenzymes must be done.

Ency. home > Test > A > ALP

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