Leucine aminopeptidase - urine

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Alternative names
LAP - urine; Urine LAP

Definition
This is a test that measures the amount of leucine aminopeptidase (LAP) in urine.

How the test is performed
A 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test (see special considerations).

• On day 1, urinate into the toilet upon arising in the morning.
  
• Collect all subsequent urine (in a special container) for the next 24 hours.
  
• On day 2, urinate into the container in the morning upon arising.
  
• Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

For an infant, thoroughly wash the area around the urethra. Open a Urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all).

The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts—lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to prepare for the test
No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel
The test involves only normal urination, and there is no discomfort.

Why the test is performed
Unlike other liver enzymes, LAP can be measured in the urine. This test may be appropriate in some cases as a screening test or to avoid the risks of having blood drawn. This test is performed much less commonly than the LAP blood test (leucine aminopeptidase - serum).

LAP is a proteolytic enzyme that breaks chemical bonds in proteins at specific sites next to leucine amino acids. Serum (blood) LAP is measured to diagnose liver dysfunction. However, LAP is made by virtually all tissues. Elevations are also seen in several cancers and systemic lupus erythematosus (SLE).

Normal Values
Normal values range from 2-18 units per 24 hours.

What abnormal results mean

Elevated levels of LAP can be seen in several conditions:

• Cholestasis
  
• Cirrhosis
  
• Hepatic (liver) ischemia (blood deficiency)
  
• Hepatic necrosis (tissue death)
  
• Hepatic tumor
  
• Hepatitis
  
• Breast cancer
  
• Endometrial cancer
  
• Ovarian cancer
  
• Germ cell tumors of the ovary and testis
  
• Systemic lupus erythematosus

What the risks are
There is essentially no risk.

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

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