Newborn Screening for Spinal Muscular Atrophy
Crystal Proud, MD: You mentioned a little bit about newborn screening, and I think we can shift our focus to talk about that and why it's so important and what it means to us. Newborn screening has begun in some states, and this means screening babies who were born in a particular state at birth to determine whether they have SMA [spinal muscular atrophy]. Julie, I'd like to ask you about your experience with this, if your state participates in newborn screening, and can you share with us the potential value that this might bring, screening babies for SMA?
Julie Parsons, MD: We are very lucky in Colorado that we screen all of the babies for Colorado and Wyoming, and our state started screening as of January this year. We've already actually had 5 babies who have been identified. I think that newborn screening is extremely important. As of last month, 23 out of our 52 states actually have pilot or implemented newborn screening programs already in place. This is something that many providers don't really understand much about or know much about, but every state has an individual process or program for setting up newborn screening.
Although the recommended uniform screening panel added SMA as a disorder to be screened for in the United States, every single state has to fund and develop and implement their own program to be able to have this process in place. In Colorado and Wyoming, all of our test results come into a single laboratory and a single provider. That certainly is different from other states that have higher populations. For instance, in Colorado we have about 60,000 to 70,000 births a year. A state like Texas would have 400,000 births. Figuring out a system for each state to manage the positive screens, I think, is important.
The newborn screen is just a blood spot. It's a done and added to the regular newborn screening that is done on every baby at the very beginning. As Nancy said, it is extremely important to be able to identify these patients early. The severe infantile form typically would present under 6 months of age, but some of the milder phenotypes, like the type IIs or the sitters or ambulatory patients, might not be identified until they're 3 or 4 years of age or even older.
We know that motor neurons are being lost during this period. As we’re going to be speaking about a little bit later, we now, fortunately, have multiple treatments that are very successful for SMA. We know that the earlier we treat the babies, the better the outcomes are, and we have seen that in the results of almost every clinical trial that has been done. So early identification is extremely important.
We also each need to work on a system of anticipating when we have a positive newborn screen how we are going to act on that positive screen and having a system in place that once the baby is identified to a primary care provider that we are able to act very quickly to implement treatment for those babies. I think that in general, we're looking at being able to identify and treat babies within about 21 days. So things need to work very quickly and efficiently to be able to effect change for these babies.
Nancy L. Kuntz, MD: Crystal, one of the things that I’m thinking that you or the others could comment on is the important continuing role for clinicians. We were talking, John and I, about the phenotype in the presentation. But newborn screening is, like the genetic testing for spinal muscular atrophy, very accurate in the greater scheme of things. It detects 95% to 98% of all infants, because it depends on the actual absence of the SMN1 gene, both copies, rather than just dysfunction.
People who have a compound heterozygote state, and therefore 1 missing and 1 nonfunctioning SMN1 gene, can still have spinal muscular atrophy. There is a role for clinicians still to be very vigilant. And if they suspect that a patient who they're seeing might have any form of spinal muscular atrophy from the infantile through the milder forms, even if there has been negative or normal newborn screening, it's important that the clinician proceed very quickly to do additional testing.
Crystal Proud, MD: I think that's a really important point to be made. In the cases where states have not yet implemented newborn screening, it is still important for us to keep in mind as we move forward that for these children who present to their pediatrician with failure to meet motor milestones, particularly if they are meeting their cognitive and social milestones and those are in contrast to their physical capacity, it's really important for those children to be referred to a neurologist for further evaluation.
I know that we all have talked extensively about the consideration of this diagnosis as a neurologic emergency. We'll talk more about therapy in a while. But we know that the sooner we intervene, potentially, the better the outcome. It is critical to be able to identify children who aren’t symptomatic and get them to be seen in a clinic on an urgent basis. This is the rationale, obviously, behind initiating newborn screening.
