To obtain a clean-catch urine sample, males should wipe clean the head of the penis and females need to wipe between the labia with soapy water and rinse well. Sometimes a special clean-catch kit is provided with cleansing solution and sterile wipes.

After urinating a small amount into the toilet bowl to clear the urethra of contaminants, collect a sample of urine in a clean or sterile container. About 1 to 2 ounces of urine is needed for a test. Remove the container from the urine stream without stopping the flow. You may finish voiding into the toilet bowl. Take the sample to the lab.

For infants:
Your infant's genital area will be cleaned and dried, then a collection device is attached to collect the urine. If you are asked to collect the urine, be sure the collection device is attached securely to prevent leakage. After your baby has urinated, the urine (at least 20 cc) is transferred to a sterile container.

This test is performed to assess amino acid levels in the urine. It is common for some of each amino acid to be in the urine, but elevated levels of individual amino acids indicates a possible inborn enzyme deficiency.

While this test shows increased levels of amino acids in the urine, a 24-hour quantitative urine chromatography is necessary to accurately measure the elevated levels of the specific amino acids.

The increased levels also show up in the blood plasma (see plasma amino acids). If the test is performed early enough on infants and the defect is treated, the severe mental retardation that can result may be prevented.