Newborn screening, often referred to as the “PKU test,” is a simple, inexpensive blood test performed on babies in the first 48 hours after birth to look for serious and often life-threatening disorders. At least 4 million babies in the United States are tested every year, and severe disorders are detected in about 3,000. Most state-required screening is free or costs a nominal fee.
Standard newborn screening consists of a small sample of blood being taken from your baby before being discharged from the hospital. The heel used to be the most common place to take the sample, so it is often called a “heel stick,” but the blood may also be drawn from the inside of the elbow. The blood should be taken around 48 hours after birth. Some tests, such as the one for PKU, may not give accurate results if it is performed too early. Because many babies are discharged early from the hospital, some babies are tested within the first 24 hours and then must be retested 1 to 2 weeks later. The blood is placed on a piece of filter paper, allowed to dry for 4 to 6 hours, and is then sent to a laboratory for analysis. The results of the screening usually take a few weeks to come back. Many labs will call the physician in the case of abnormal results, while normal results will be sent in the mail.
Newborn screening tests for disorders that can cause mental retardation, severe illness, and premature death if not detected at birth. For example, hypothyroidism is the most common disorder identified by routine screening, affecting 1 baby in 3,000. Congenital hypothyroidism is a thyroid hormone deficiency that retards growth and brain development; but if it is detected in time, the baby can be treated with oral doses of thyroid hormone to permit normal development.
If your baby’s test results come back as abnormal, try not to be overly alarmed; the initial screening tests give only preliminary information that must be followed up by more precise testing. False-positive results are possible with newborn screening and most babies turn out to be normal after further testing.
There is currently no federal standard for which disorders newborns are tested, and as a result, screening varies widely from state to state. However, all states screen for at least two disorders: phenylketonuria (PKU) and hypothyroidism, and many states include sickle cell anemia, galactosemia, and homocystinuria.
Expanded newborn screening (ENBS) is available through private companies and laboratories for an additional charge and uses Tandem Mass Spectrometry (MS/MS) to test for up to 40 rare disorders. ENBS is expensive and most states don’t have the highly-trained experts required to run the very specialized screenings and then effectively and accurately interpret the results; therefore, it is not available in all areas. In addition, there are no cures or known treatments for many of the disorders for which ENBS screens.
However, you can request ENBS if you feel you are at a higher risk for a disorder. If you answer yes to any of the following questions, you may want to discuss ENBS with your doctor:
- Do you have a family history of an inherited disorder?
- Have you previously given birth to a child who’s affected by a disorder?
- Did an infant in your family die because of a suspected metabolic disorder?
- Do you have another reason to believe that your child may be at risk for a certain condition?
To find out which disorders your state screens for, visit the National Newborn Screening & Genetics Resource Center Website.