BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuSerum phenylalanine screeningPhenylalanine - blood test; PKU - phenylalanineSerum phenylalanine screening is a blood test to look for signs of the disease phenylketonuria (PKU). The test detects abnormally high levels of an amino acid called phenylalanine.PhenylketonuriaPhenylketonuria (PKU) is a rare condition in which a baby is born without the ability to properly break down an amino acid called phenylalanine....Read Article Now Book Mark Article How the Test is Performed The test is most often done as part of routine screening tests before a newborn leaves the hospital. If the child is not born in a hospital, the test should be done in the first 48 to 72 hours of life.An area of the infant's skin, most often the heel, is cleaned with a germ killer and punctured with a sharp needle or a lancet. Three drops of blood are placed in 3 separate test circles on a piece of paper. Cotton or a bandage may be applied to the puncture site if it is still bleeding after the blood drops are taken.The test paper is taken to the laboratory, where it is mixed with a type of bacteria that needs phenylalanine to grow. Another substance that blocks phenylalanine from reacting with anything else is added.Newborn screening tests is a related article.Newborn screening testsNewborn screening tests look for developmental, genetic, and metabolic disorders in the newborn baby. This allows steps to be taken before symptoms ...Read Article Now Book Mark Article How to Prepare for the Test For help preparing your baby for the test, see infant test or procedure preparation (birth to 1 year).Infant test or procedure preparationBeing prepared before your infant has a medical test can help you know what to expect during the test. It will also help reduce your anxiety so that...Read Article Now Book Mark Article How the Test will Feel When the needle is inserted to draw blood, some infants feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Infants are given a small amount of sugar water, which has been shown to reduce the painful sensation associated with the skin puncture. Why the Test is Performed This test is done to screen infants for PKU, a fairly rare condition that occurs when the body lacks a substance needed to breakdown the amino acid phenylalanine.If PKU is not detected early, increasing phenylalanine levels in the baby will cause intellectual disability. When discovered early, changes in the diet can help prevent the severe side effects of PKU. Normal Results A normal test result means that phenylalanine levels are normal and the child does not have PKU.Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your baby's test results. What Abnormal Results Mean If the screening test results are abnormal, PKU is a possibility. Further testing will be done if the phenylalanine levels in your baby's blood are too high. Risks The risks of having blood drawn are slight, but include:Excessive bleeding Fainting or feeling lightheaded Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken) Multiple punctures to locate veinsOpen ReferencesReferencesKonczal LL, Zinn AB. Inborn errors of metabolism. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 90.McPherson RA. Specific proteins. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 20.Pasquali M, Longo N. Newborn screening and inborn errors of metabolism. In: Rifai N, ed. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. St Louis, MO: Elsevier; 2018:chap 70.AllVideoImagesTog Tests for Serum phenylalanine screening Serum phenylalanine screeningRelated Information Phenylketonuria(Condition) Review Date: 5/24/2021 Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- © 1997- All rights reserved. A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.Content is best viewed in IE9 or above, Firefox and Google Chrome browser.