Plasma amino acids
Key points
- This is a screening test performed on infants that detects problems with amino acid metabolism.
- The area (usually the heel) is cleansed with antiseptic and the skin is punctured with a sharp needle or a lancet.
- Fast for 4 hours before the test, or the test results may be altered and invalidated.
- When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation.
Alternative names
Amino acids - plasma
Definition
This is a screening test performed on infants that detects problems with amino acid metabolism.
How the test is performed
The area (usually the heel) is cleansed with antiseptic and the skin is punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
Chromatography is then used to analyze the amino acids in your child's blood.
How to prepare for the test
Fast for 4 hours before the test, or the test results may be altered and invalidated.
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation.
The needle insertion will probably make your infant cry briefly.
Why the test is performed
Amino acids are the building blocks for proteins in the body. Accumulation of amino acids can occur due to abnormalities in the normal mechanisms for their metabolism or elimination. The increased levels show up in plasma (the liquid portion of blood) and urine.
If the test to identify and measure their quantities is performed early enough on an infant with an inherited defect in amino acid metabolism, treatment can often be administered to prevent the severe mental retardation that may otherwise result.
Normal Values
- alanine
o children: 200 to 450
o adults: 230 to 510 - alpha-aminoadipic acid
o children: not measured
o adults: not measured - alpha-amino-N-butyric acid
o children: 8 to 37
o adults: 15 to 41 - arginine
o children: 44 to 120
o adults: 13 to 64 - asparagine
o children: 15 to 40
o adults: 45 to 130 - aspartic acid
o children: 0 to 26
o adults: 0 to 6 - beta-alanine
o children: 0 to 49
o adults: 0 to 29 - beta-amino-isobutyric acid
o children: not measuredo adults: not measured
Written and revised by
David Cohen, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
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