Leucine aminopeptidase - serum

Definition

Serum leucine aminopeptidase is a blood test that measures the amount of the enzyme leucine aminopeptidase (LAP).

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell 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 band 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.

In infants or young children:

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. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test

The health care provider may tell you to stop taking any drugs that could affect the test.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

LAP is an enzyme normally found in liver cells (hepatocytes). It is also released into the blood after damage to liver cells, such as from drugs or infection (for example, hepatitis). Measurement of LAP in blood may serve as an indicator of liver damage.

LAP may also be released into blood by tumors that arise in the liver, so it may also serve as a tumor marker or indicator.Other enzymes, such as ALT, AST, ALP, LDH, and GGT, are more commonly measured for the same purpose.

Testing serum LAP is generally not as sensitive or as convenient as testing 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

• Cholestasis
• Cirrhosis
• Hepatic (liver) ischemia (blood deficiency)
• Hepatic necrosis (tissue death)
• Hepatic tumor
• Hepatitis

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.

Illustrations

Blood test

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Serum leucine aminopeptidase