Yes, the Newborn Screen is often referred to as the PKU test, but this is an outdated term. PKU (PhenylKetonUria) was the very first condition screened for by newborn screening in 1965. Since this time, many more conditions have been added to the test, which is why it should be referred
to as the Newborn Metabolic Screen. Calling the screen the PKU test might be confusing for families or other providers, and children may be incorrectly initially labeled as having PKU when, in fact, they have a different condition on the Newborn Metabolic Screen.

 

Historically, the 2nd screen was initiated because many babies were discharged before 24 hours of age and, therefore, did not have a satisfactory initial screen. The 2nd screen is important in these cases so that a baby can have at least one satisfactory screen. Over the years, the two screen system has been supported by the fact that about 10% of congenital hypothyroidism is identified by testing the second (subsequent) screen. The 2nd screen may also pick up milder variants that are not evident at the time of the initial screen. The 2nd screen picks up several children each year with conditions that are not detectable on the initial screen.

 

Beginning in 2006, the state of Maryland began testing for cystic fibrosis (CF) by implementing the IRT/IRT system. Using this system, two elevated IRT levels are needed to determine if a baby is at increased risk for cystic fibrosis. This means that the two screen system is a vital part of CF testing

 

The first Newborn Metabolic Screen (NBS) should be collected when the baby has had 24 hours of feeding. Ideally, this is the day the baby is discharged from the hospital. The 2nd screen should be collected when a baby is greater than 7 days old, ideally between 10 days and two weeks. A screen collected at less than 24 hours is not a valid for several conditions on the NBS.

 

All babies admitted to the NICU should have a Newborn Metabolic Screen collected as soon as possible after admission. The Newborn Metabolic Screen should be collected prior to transfusion and initiation of antibiotics. Additional screens should be collected between 2-3 days of age, at the 10 day interval, and then again at 1 month or discharge (whichever comes first).

 

The cutoff values that the laboratory uses are only valid for babies that are 8 weeks of age or less. If you send a screen on a baby older than 8 weeks, the laboratory does not have appropriate cut-offs for interpretation. However, if there is an elevation, the follow-up staff will contact you to make recommendations.

 

There are over 50 conditions on the Newborn Screen. Click here to learn more.

 

Timing is crucial in newborn screening so that babies are identified and treated as soon as possible BEFORE they get sick. If you are contacted by someone at the health department about an abnormal screen, please do not delay and get the baby in as soon as possible. The follow-up team at the health department can give you more details when they call you about an abnormal result.

 

There are many specialists available to help if you have questions about a Newborn Screen or if you need to refer a baby. For a list of providers that can help you, click here. The staff of the Newborn Screening Follow-Up Program is also always available to assist you with these referrals.

 

Sometimes a level is elevated on the NBS, but it is not high enough to be considered an “urgent abnormal” result. In these situations, the text of the report itself will request that you collect a repeat Newborn Screen, and you will not receive a call from the follow-up team. IT IS IMPORTANT that you READ EACH REPORT to assure that you follow-up appropriately with borderline results. A borderline result is still not normal and should still be followed up promptly with a repeat screen. If you have questions the follow- up team members are always available to help you.

 

Results are not usually called out to providers when babies have an abnormal first screen for cystic fibrosis, represented by an elevated Immunoreactive Trypsinogen (IRT). The newborn metabolic screening result report is sent out calling the level ‘borderline’ and asking for a repeat to be collected. A baby is not considered to have a positive screen for cystic fibrosis until the baby has two abnormal IRT levels. Ideally the first is collected at the birth hospital and the 2nd should be collected after 10 days. IT IS IMPORTANT that you READ EACH REPORT to assure that the baby is followed appropriately.

 

If a baby has an unsatisfactory initial Newborn Metabolic Screen, you should recall the patient ASAP to get a repeat screen. Remember, the purpose of newborn screening is to identify babies before they ever get sick. Just because a baby looks well at a few days of age does not mean they will have a normal Newborn Screen. Many babies who have disorders on the Newborn Screen look healthy for a few days before they get sick.