Definition

The leucine aminopeptidase (LAP) test measures how much of this enzyme is in your blood.

Your urine can also be checked for LAP.

Alternative Names

Serum leucine aminopeptidase; LAP - serum

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

You need to fast for 8 hours before the test. This means you can't eat or drink anything during the 8 hours.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

LAP is a type of protein called an enzyme. This enzyme is normally found in cells of the liver, bile, blood, urine and the placenta.

Your health care provider may order this test to check if your liver is damaged. Too much LAP is released into your blood when you have a liver tumor or damage to your liver cells.

This test is not done very often. Other tests, such as gamma-glutamyl transferase, are as accurate and easier to get.

Normal Results

Normal range is:

• Male: 80 to 200 U/mL
• Female: 75 to 185 U/mL

Normal value ranges may vary slightly. Some labs use different measurement methods. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result may be a sign of:

• Bile flow from the liver is blocked (cholestasis)
• Cirrhosis (scarring of the liver and poor liver function)
• Heart Failure
• Hepatitis (inflamed liver)
• Liver cancer or tumor
• Liver ischemia (reduced blood flow to the liver)
• Liver necrosis (death of liver tissue)
• Use of medicines that are toxic to the liver

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Daniels L, Khalili M, Gordstein E, Bluth MH, Browne WB, Pincus MR. Evaluation of liver function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 22.

Korneblat KM, Berk PD. Approach to the patient with jaundice or abnormal liver tests. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 138.