PKU Test

What is it?

The PKU test is  another  common procedure performed by obtaining a newborn blood sample via heel stick to screen the baby for Phenylketonuria (PKU) and other metabolic disorders.  All states currently screen for PKU,  hypothyroidism and galactosemia and some screen for  sickle cell anemia and congenital adrenal hyperplasia (CAH)  as well.  In other states, as many as 30 metabolic disorders will be ruled out.

Why is it done?

This screening is used to determine the presence of serious metabolic disorders which can be fatal or debilitating if not caught and treated early.  PKU, or Phenylketonuria, is one of the primary offenders that is ruled out by this screening.  Other disorders can all have devastating effects if not caught and treated early.


When completed by a skilled nurse or phlebotomist, the baby may not even wake after the stick.  To ensure that the baby only needs one stick, make sure that the baby's heels are very warm to increase blood flow to the area.  This procedure will have to be repeated if a large enough sample isn't obtained the first time.


Koch R, Wenz E. Phenylketonuria. Annu Rev Nutr 1987;7:117-35.

Lenke RR, Levy HL. Maternal phenylketonuria and hyperphenylalaninemia. An international survey of the outcome of untreated and treated pregnancies. N Engl J Med 1980;303:1202-8.

Guthrie R. Blood screening for phenylketonuria. JAMA 1961;178:863.

Jew K, Kam K, Koch R, Cunningham GC. Validity of screening early collected newborn specimens for phenylketonuria using a fluorometric method. Screening 1994;3:1-9.

American Academy of Pediatrics Committee on Genetics. Newborn screening fact sheet. Pediatrics 1996;98:473-501.

Platt LD, Koch R, Azen C, Hanley WB, Levy HL, Matalon R, et al. Maternal phenylketonuria collaborative study, obstetric aspects and outcome: the first six years. Am J Obstet Gynecol 1992;166: 1150-60.

Koch R, Wenz E, Bauman C, Friedman EG, Azen C, Fishler K, et al. Treatment outcome of maternal phenylketonuria. Acta Paediatr Jpn 1988;30: 410-6.

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