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Plasma amino acidsDefinition Plasma amino acids 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 Infant should not be fed 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
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 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:
What the risks are Risks associated with having blood drawn are slight:
Illustrations
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