Health Encyclopedia

Plasma amino acids

Definition

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.

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.

How the test will feel

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 Values

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.

What abnormal results mean

An increase in the total level of amino acids in the blood amino may be due to:

Eclampsia
Fructose intolerance
Ketoacidosis (from diabetes)
Kidney failure
Reye syndrome

A decrease in the total level of amino acids in the blood may be due to:

Adrenal cortical hyperfunction
Fever
Hartnup disease
Huntington's chorea
Malnutrition
Nephrotic syndrome
Phlebotomus fever
Rheumatoid arthritis

What the risks are

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)

Special 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:5/25/2007
Reviewed By:Daniel R Alexander, MD, Department of Internal Medicine, St. Mary's Hospital, Leonardtown, MD. Review provided by VeriMed Healthcare Network.

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