Definition This is a test to measure the level of amino acids in the urine. Amino acids are the building blocks that combine to form proteins.
Who is a candidate for the test? This test is usually ordered when a doctor suspects an inborn error of metabolism. These disorders can affect the level of certain amino acids in the urine. There are over 20 different amino acids. Each disorders can affects the level of different amino acids in the urine. This test is generally performed on infants and young children, because most of these disorders tend to cause symptoms shortly after birth.
This test may also be done to monitor persons with known amino acid disorders.
How is the test performed? To perform this test, a urine sample is needed. A person is asked to supply urine in a special container. Advice on how to get a urine sample from an infant is provided if needed. The urine sample is taken to a laboratory for testing.
What is involved in preparation for the test? Generally, no preparation is needed. The doctor will give instructions if needed.
What do the test results mean? There are over 20 different amino acids in the urine. A low level of amino acids is normal in the urine. If the level for one or more amino acids is higher than normal, there may be an inherited disorder present.
In some cases, early detection in the first year of life can prevent problems such as brain damage from occurring.
The exact levels of each of the amino acids in the urine helps figure out the specific disorder. Further tests, such as blood tests, may be needed to confirm the suspected disorder.
Examples of specific disorders that can cause abnormal test results include:
phenylketonuria (PKU). This disorder can cause severe mental retardation in the first year of life, which can be prevented with treatment. In Australia, babies are screened for this disorder at birth. This allows the earliest possible detection and treatment.
cystinuria. This is a fairly common disorder that causes few health problems. Affected people are more likely to form kidney stones.
Hartnup disease. This disorder may cause brain damage when untreated. However, appropriate treatment with vitamins can prevent problems.
There are many other rare inherited disorders that can cause abnormal test results. Other diseases of the kidney can also cause abnormal test results. Results should be discussed with the doctor.
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 25/05/2005 Contributors Potential conflict of interest information for reviewers available on request
