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Blood test
Blood test

Leucine aminopeptidase - serum
Definition:
A test that measures the amount of the enzyme leucine aminopeptidase (LAP) in the blood.

Alternative Names:
Serum leucine aminopeptidase

How the test is performed:
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test:
The health care provider may advise you to discontinue drugs that can affect the test (see "Special considerations").

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed:

LAP is a proteolytic enzyme that breaks chemical bonds in proteins at specific sites next to leucine amino acids.

LAP is normally found in liver cells (hepatocytes). However, LAP is released into the blood after damage to liver cells such as from drugs or infection (i.e., hepatitis). Measurement of its level in blood may serve as an indicator of liver damage. This enzyme can also be released into blood by tumors that arise in the liver possibly serving as a tumor marker.

Other enzymes such as ALT, AST, ALP, LDH, and GGT are more commonly measured for the same purpose. Serum LAP is generally not as sensitive or as convenient as other liver enzymes to detect some liver problems. Unlike other liver enzymes, LAP can be measured in the urine (see LAP - urine).
Normal Values:
  • male: 80 to 200 U/ml
  • female: 75 to 185 U/ml
Note: U/ml = units per milliliter
What abnormal results mean:
What the risks are:
  • excessive bleeding
  • fainting or feeling light-headed
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins
Special considerations:

Drugs that can affect LAP measurements include estrogens and progesterones.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Review Date: 11/26/2001
Reviewed By: Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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