After Lucas’s newborn screen, I wanted an answer. I wanted to know what they’d found and what it meant for him. It took me a while to understand how many different questions were wrapped up in that. If the word you’ve just heard is “borderline,” start by asking which result the team is talking about.
Here are the questions I’d start with. What exactly came back borderline? What could the next test tell us? When do we need to do it, and when should we expect to hear back? It helped me to know which question we were trying to answer first.
Why might my baby need a repeat sample?
Some screening programs use a cutoff for a measured substance in the blood. A result may be in range, out of range, or borderline, depending on the program and condition. The cutoff helps the program decide who needs another sample or a referral. Your baby’s team can explain what the result means and how quickly to follow up. HRSA’s screening results guide
The NHS newborn blood spot guidance for congenital hypothyroidism gives one example. An initial thyroid-stimulating hormone result in its borderline range generally calls for another blood spot sample. A result in its positive range calls for referral. Those are rules for that program and condition. Ask your own team which rules apply to your baby. UK congenital hypothyroidism referral guidance
Borderline results, false positives, and uncertain genetic findings
Sometimes follow-up shows the baby does not have the condition the screen flagged. That’s a false positive. In some cases, uncertainty remains after follow-up. In cystic fibrosis, for example, a positive screen and inconclusive diagnostic testing can lead to a designation called CRMS/CFSPID. There is specific follow-up guidance for those children. Cystic Fibrosis Foundation guidance
A variant of uncertain significance, or VUS, describes uncertainty about a change found in a gene. A VUS by itself does not establish a diagnosis. That’s a different question from whether a screening measurement fell near a cutoff. There can also be uncertainty about if or when symptoms will develop, even after a condition is confirmed. For ALD, an initial screen cannot tell you which symptoms a child might develop. MedlinePlus on genetic test results · International ALD recommendations
Related guide: ALD newborn screening guide.