Newborn Screening
The newborn screen – also known as the ‘PKU’ or ‘heel stick’ – is a test done on all babies born in the US at about 24 hours old, and again at about two weeks old. Most people know that it’s important, but not everyone knows what it’s actually for.
First, what do we mean by ‘screening’?
A ‘screen’ is a very specific kind of test where a large number of apparently healthy people are checked for a particular condition – blood pressure checks and mammograms are examples of screens. The condition has to be something that, if detected early, can be fixed or treated so the person can have a better, healthier life. The condition should be a big enough problem, and be common enough that screening is cost effective. The screening test itself needs to be good enough that it will identify most people with the disease, but not falsely identify healthy people as positive. There will always be some false positives, to get as many affected people as possible.
Why did we start screening?
In the 1970’s it was noted that while children with phenylketonuria (PKU) became severely mentally delayed, if they were treated with a particular diet starting from birth, most of that could be avoided. Thus, the newborn screen was started.
Who does the screening?
Each state is responsible for their own newborn screening program. They decide what to screen for, where the screens are sent to be processed, and what official follow up to take. They are also responsible for funding.
What is screened?
Since each state chooses their own screening panel, the Advisory Committee on Heritable Disorders in Newborns and Children was developed to give expert guidance. So far, they recommend 35 conditions in the uniform panel. The conditions recommended can change or be added to depending on the committee’s recommendations.
The conditions can be loosely grouped in a few different categories:
–Inborn errors of metabolism (IEB). Your cells use and store energy in a complex series of steps. A problem with any of these steps can make it hard for the body to get energy and/or cause buildup of byproducts that can damage the body.
–Abnormal hemoglobin. Hemoglobin helps your blood carry around oxygen to all the organs. If the hemoglobin is abnormal, it can’t carry as much oxygen, and is often broken down quicker.
–Other. This includes a few conditions that don’t fit into the other two categories. These are things like congenital hypothyroidism, cystic fibrosis, critical congenital heart defects (CHD), and hearing loss.
How are they tested?
The hearing screen and CHD tests are easily done in the nursery. The hearing screen is done by sensing the baby’s response to a noise made in the ear. The CHD screen is done by comparing the baby’s blood oxygen levels in the hand and the foot. A nurse uses a soft band around the hand or foot to check the level.
The rest of the tests are blood tests. The baby’s heel is stuck, and the blood is used to fill circles on the screening card. The card is then sent to a lab for testing.
How long does it take to get the results?
The results of the hearing screen and heart disease screening will be known before the baby is discharged. Otherwise if a baby turns out to have an abnormal test, you and your pediatrician will be notified within a few days. If the test is normal, it often takes several weeks.
What happens if a child has an abnormal test?
For many abnormal tests, we can just wait for the second newborn screen to be done. Often the second one will come back normal. If the test is significantly abnormal, or still abnormal at the second screen, then confirmatory testing may be done and the child will be referred to the appropriate specialist.
Bottom line.
Newborn screening is an important way to identify some children who need special treatment before their conditions become a problem.
Links.
Recommended uniform screening panel.
Congenital heart disease screening.
