Leucine aminopeptidase - serum

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:
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 experience, 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 it Feels:
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 .

Risks:

  • excessive bleeding
  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins



Why this Test is Performed:
Serum LAP is measured to diagnose liver ( hepatic ) dysfunction.

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

Other enzymes such as ALT , AST , ALP , LDH , and GGT are measured for the same purpose, but LAP is thought to be a liver-specific enzyme. For example, if a person has an elevated serum ALP or LDH, the physician may order an LAP test to determine whether the abnormality is localized to the liver vs. the bone or muscle . Serum LAP is not as sensitive or as convenient as other liver enzymes to measure for some liver problems, but it does seem to be a sensitive measure of cholestasis (that is, congestion of the bile ducts). Also, 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

Abnormal Results:



Cost:
Information not available.

Special Considerations:
Drugs that can affect LAP measurements include estrogens and progesterones (see Progestins - oral).

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.