MedlinePlus Medical Encyclopedia: Plasma amino acids

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Plasma amino acids

Contents of this page:
Illustrations Alternative names Definition How the test is performed How to prepare for the test	How the test will feel Why the test is performed Normal Values What abnormal results mean What the risks are

Illustrations

Amino acids

Alternative names Return to top

Amino acids - plasma

Definition Return to top

This is a screening test performed on infants that detects problems with amino acid metabolism.

How the test is performed Return to top

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 Return to top

Fast for 4 hours before the test, or the test results may be altered and invalidated.

How the test will feel Return to top

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 Return to top

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 Return to top

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

Note: all measurements in micro mole per liter (micro mol/L); The normal range of values may vary between different laboratories, and the laboratory performing the test should therefore be consulted in interpretation of the test result.

What abnormal results mean Return to top

An elevated level of a particular amino acid is highly suggestive of an inherited defect in metabolism of that amino acid. The test for an individual amino acid may also be used for following the effectiveness of a particular treatment.

If the total amino acid level is elevated, several diseases or conditions may be the cause:

If the total amino level is decreased, the following conditions may be responsible:

fever
malnutrition
rheumatoid arthritis
Hartnup disease
Huntington's chorea
phlebotomus fever
nephrotic syndrome
adrenal cortical hyperfunction

What the risks are Return to top

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)

Update Date: 9/3/2003

Updated by: Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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