PKU TEST

What is the PKU test? 

The PKU test (phenylketonuria ) screens for certain metabolic and genetic disorders in the newborn, some of which can be treated with dietary changes.  It includes more than just the PKU test, depending upon which state you are in.  Phenylketonuria and congenital hypothyroidism are screened in all fifty states, however Kansas and Missouri include the following tests:

·        Phenylketonuria (PKU): PKU is a disorder where an essential amino acid (phenylalanine) cannot be broken down by the body due to a lack of a certain enzyme.  Symptoms do not appear until sufficient milk feedings have been ingested; usually a minimum of 24 hours of formula or mature breastmilk.  Breastfed babies must be tested again a month later.  Unseen problems such as brain damage may develop over a few weeks or months, but can be prevented by a special diet low in phenylalanine.  Other neurological problems may not be noticable until around 6 to 20 months of age. The disorder may also block normal pigmentation, thus albinoism may accompany PKU, as well as musty or mousy-odor urine, which does not begin until 4 to 6 weeks of age, after brain damage has already begun. PKU is most common in people of Northern Ireland or Western Scotland.  It occurs in about 1 of every 12,000 newborns.

·        Galactosemia: Galactosemia is caused by a deficient or defective liver enzyme. A milk sugar (galactose) cannot be broken down by the body due to the lack of an enzyme.  Symptoms such as failure-to-thrive, lethargy, sepsis, gastrointestinal upset, jaundice may appear in as little as a few days after milk feeding begins.  If left untreated, mental retardation, speech disorders, growth and developmental delays, and ovarian failure in girls may develop.  A diet low in galactose can prevent life-threatening complications.  Occurs in about 1 of every 60,000 newborns.

·        Hypothyroidism:  Inadequate production of a hormone (thyroxine) can lead to mental and growth retardation.  This is especially common in Down Syndrome babies.  Other symptoms at birth include an enlarged tongue, puffy face, distended abdomen and umbilical hernia.  Constipation, abdominal distention and vomiting, and jaundice may appear after 3 days of age.  Symptoms may be delayed in breastfed babies due to small amounts of thyroid hormone present in breastmilk.  Treatment is daily thyroxine tablets.  Occurs in about 1 of every 4,000 newborns.

·        Hemoglobinopathies: Presence of an unusual hemoglobin (red blood cell).  Most unusual hemoglobins do not require treatment.  Sickle cell disease is an unusual hemoglobin that requires antibiotic treatment to prevent life-threatening infections.

How is the test done?  The test is done by pricking the heel of the newborn, usually at the 3-day postpartum visit.  Enough blood must be let in order to fill five circles on the testing card.  This usually requires usage of a special lancet called a Tenderfoot (or similar device) that actually takes a small “slice” in the foot.  The test card is then allowed to dry and is mailed to the health department at the address on the card.  The results can either be mailed to the mother or to the pediatrician you list on the card.  I can complete this test for your child, but because I am philosophically opposed to intentionally harming a newborn, I ask that a parent be the one to lance the child.