Leucine Aminopeptidase Test-Why am I having this test?

Leucine aminopeptidase test (LAP) is used to help diagnose liver disorders. You may have this test if you have symptoms of a liver disorder such as nausea or weight loss.

What is being tested?

This test checks for the presence of LAP in the blood. LAP is an enzyme in the liver, pancreas, and small intestine. When disease or injury affects these organs, LAP is released into the blood.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

This test may also be done using a urine sample. You may be asked to collect urine samples at home over a period of 24 hours. Follow instructions from a health care provider about how to collect the samples.

How do I collect samples at home?

When collecting a urine sample at home, make sure you:

• Use supplies and instructions that you received from the lab. 
• Collect urine only in the germ-free (sterile) cup that you received from the lab. 
• Do not let any toilet paper or stool (feces) get into the cup.
• Refrigerate the sample until you can return it to the lab. 
• Return the sample(s) to the lab as instructed.

How do I prepare for this test?

Follow instructions from your health care provider about eating or drinking restrictions. You may need to stop eating and drinking everything except water starting 8 hours before your test.

How are the results reported?

Your test results will be reported as a value that indicates how much LAP is in your blood. This will be given as units of LAP per milliliter of blood (units/mL) or units of LAP per liter of blood (units/L). If you had a urine sample tested, your results will be given as units of LAP in the urine during the 24-hour period.

Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• Blood:
  • Male: 80–200 units/mL or 19.2–48 units/L (SI units).
  • Female: 75–185 units/mL or 18–44.4 units/L (SI units).
• Urine: 2–18 units/24 hours.

What do the results mean?

Results that are within your reference range are considered normal. This means that there is a normal amount of LAP in your body, and your liver, pancreas, and intestines are not affected by disease or injury.

Results that are higher than your reference range mean that there is too much LAP in your blood. This may be caused by:

• Liver disease.
• Liver cancer.
• Liver failure.
• Drugs or medicines that are poisonous (toxic) to the liver.
• Gallstones (cholelithiasis).
• Pregnancy.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• The leucine aminopeptidase (LAP) test is used to help diagnose liver disorders.
• Your test results will be reported as a value that indicates how much LAP is in your blood.
• Results that are higher than your reference range mean that there is too much LAP in your blood.