Plasma amino acids

Alternative names:

amino acids - plasma

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:

Certain enzymes convert or combine with amino acids, creating other products that the body can use. If an amino acid enzyme is not present, that particular amino acid continues to accumulate. The increased levels show up in plasma amino acids and in the urine, as a test reveals. If the test is performed early enough on infants and the defect is treated, the severe mental retardation that can result may be prevented.