Plasma amino acids is a screening test done on infants that looks at the amounts of amino acids in the blood. Amino acids are the building blocks for proteins in the body.
See also:
Amino acids - urine
Inborn errors of metabolism
Newborn screening tests
Alternative Names
Amino acids blood test
How the Test is Performed
A blood sample is needed. The area (usually the heel) is cleansed with germ-killing solution, and the skin is punctured with a sharp needle or a lancet. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
The blood sample is sent to a lab. Chromatography is used to determine the amino acids levels in the blood.
How to Prepare for the Test
The baby should not be fed for 4 hours before the test.
The needle stick will probably cause the infant to cry.
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
This test is done to measure the level of amino acids in the blood.
An increased level of a particular amino acid is a strong sign that there is a problem with the body's ability to break down (metabolize) that amino acid.
The test may also be used to look for decreased levels of amino acids in the blood, which may occur with fevers, inadequate nutrition, and certain medical conditions.
Normal Results
All measurements are in micromole per liter (micro mol/L). Normal values may vary between different laboratories. Talk to your doctor about your specific test results.
Alanine
Children: 200 to 450
Adults: 230 to 510
Alpha-aminoadipic acid
Children: not measured
Adults: not measured
Alpha-amino-N-butyric acid
Children: 8 to 37
Adults: 15 to 41
Arginine
Children: 44 to 120
Adults: 13 to 64
Asparagine
Children: 15 to 40
Adults: 45 to 130
Aspartic acid
Children: 0 to 26
Adults: 0 to 6
Beta-alanine
Children: 0 to 49
Adults: 0 to 29
Beta-amino-isobutyric acid
Children: not measured
Adults: not measured
Carnosine
Children: not measured
Adults: not measured
Citrulline
Children: 16 to 32
Adults: 16 to 55
Cystine
Children: 19 to 47
Adults: 30 to 65
Glutamic acid
Children: 32 to 140
Adults: 18 to 98
Glutamine
Children: 420 to 730
Adults: 390 to 650
Glycine
Children: 110 to 240
Adults: 170 to 330
Histidine
Children: 68 to 120
Adults: 26 to 120
Hydroxyproline
Children: 0 to 5
Adults: not measured
Isoleucine
Children: 37 to 140
Adults: 42 to 100
Leucine
Children: 70 to 170
Adults: 66 to 170
Lysine
Children: 120 to 290
Adults: 150 to 220
Methionine
Children: 13 to 30
Adults: 16 to 30
1-methylhistidine
Children: not measured
Adults: not measured
3-methylhistidine
Children: 0 to 52
Adults: 0 to 64
Ornithine
Children: 44 to 90
Adults: 27 to 80
Phenylalanine
Children: 26 to 86
Adults: 41 to 68
Phosphoserine
Children: 0 to 12
Adults: 0 to 12
Phosphoethanolamine
Children: 0 to 12
Adults: 0 to 55
Proline
Children: 130 to 290
Adults: 110 to 360
Serine
Children: 93 to 150
Adults: 56 to 140
Taurine
Children: 11 to 120
Adults: 45 to 130
Threonine
Children: 67 to 150
Adults: 92 to 240
Tyrosine
Children: 26 to 110
Adults: 45 to 74
Valine
Children: 160 to 350
Adults: 150 to 310
What Abnormal Results Mean
An increase in the total level of amino acids in the blood amino may be due to:
High or low concentrations of individual plasma amino acids must be interpreted along with other clinical information. Abnormal results may be due to diet, hereditary problems with the ability of the body to handle the amino acid, or to drug effects.
Risks
Risks associated with having blood drawn are slight:
Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Considerations
Screening infants for increased levels of amino acids can lead to early diagnosis of inborn errors of metabolism. Early treatment for such conditions may prevent complications such as severe mental retardation.
Review Date:
5/20/2009
Reviewed By:
Frank A. Greco, M.D., Ph.D., Director, Biophysical Laboratory, The Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.