Four days after my daughter was born in October of this year, I received a call from the hospital. They wanted us to take her daughter back right away to redo the newborn screening test. Her initial tests revealed that she had very few T cells, an important part of the immune system. All doctors assured us that this test was very likely to be a false positive, but they wanted us to avoid live virus vaccination while waiting for retesting.
I don’t want to alarm you all, but a retest two weeks later showed that it was indeed a false positive and she was perfectly fine. But her two weeks is a very long time for anxious new parents, and while waiting for answers, I spent a lot of time learning more than anyone ever wanted to know about the U.S. newborn screening program. spent. This is one of the most impressive achievements of our health care system, and it’s something parents usually never have to think about, unless there’s a compelling reason to do so.
The extraordinary balancing act of screening for rare diseases
When a baby is born in California, where my family lives, a nurse takes a small blood sample from a puncture wound in the leg and sends it to a lab. There, dried blood spots are tested for more than 80 serious but treatable genetic diseases. (Most states have similar systems, but the exact details of testing vary by state.) Here’s one of his: SCID, or severe combined immunodeficiency, you may have heard of it as “bubble boy” disease. Although SCID can be inherited, it is often the result of a genetic mutation; Affects 1 in 58,000 infants.
If SCID is not identified, babies with SCID may Death usually occurs within the first year of life due to infection. However, if caught early enough, there are now treatment options to properly treat your baby. Chance of survival is 80% to 95%. This is exactly the type of disease that newborn screening programs target. In other words, it is fatal if not detected early, but it is treatable if detected early.
But to understand the immense challenges of effectively screening for SCID, we need to take a look at the mathematics of rare disease screening. Imagine there is a test that identifies all his SCID babies in the entire United States, and the false positive rate is 1 percent. This means that if your baby is perfectly healthy, the test will return a 1 for “perfectly healthy” 99 percent of the time. The probability that a test will incorrectly determine that your immune system is weakened. For every 58,000 babies, we will find one actual case of SCID and 580 false positives. With doctors testing for about 80 different genetic disorders, nearly every family is at increased risk of being incorrectly told that their baby may have a serious illness. Masu.
To test for conditions that are sufficiently rare, it is not enough for a test to be 99% reliable. We want confidence on the order of 99.9%, but the number of false positives still outweighs the number of true positives by 60:1. This means that screening for rare conditions at a population level requires very high test reliability.
That’s not the only restriction. The test must be viable on a single spot of dried blood. Because the test is performed on every newborn, the test must be inexpensive. It also needs to be automatable, as tests need to be processed quickly.
By all these criteria, testing for SCID is a victory for medicine.only 0.08% of infants require a second test, which has a very low false positive rate. This test, like many other newborn screening tests, can be performed inexpensively on a single blood spot. And the test reliably identifies babies who would otherwise die before they can be saved.
As a result, a disease that was always fatal just a few decades ago now has such a high survival rate that most parents don’t even know their child has been tested for it.
Progress and rare diseases
Having a baby is a humbling experience. For us, part of the experience was a reminder of how much medical progress has been made behind the scenes. I had heard about “bubble boy” disease, but I had no idea it could now be treated so effectively. I had no idea how much engineering work went into getting these tests to an exceptionally reliable and affordable standard.
In the world of technology, while digital technology advances,Progress in the atomic world is limitedFrom airplanes to homes to schools, physical things make a big difference in our lives. But I think it’s easy to underestimate progress when it’s intentionally largely invisible.
Decades ago, SCID was a deadly diagnosis, but that is no longer the case. Until pilot studies began in 2008 and 2010, there were no inexpensive and reliable testing methods, but there are now. Until 2019, this test was not carried out nationally, but it is now being carried out. Unless your child has a rare genetic disease, you probably haven’t had a chance to think about how far we have come in detecting and treating such diseases – and in fact, researchers… has worked very hard to make sure you don’t have to think about it by designing tests that have extremely few false positives.
All of this progress can be measured in lives. The infant mortality rate for the entire United States was approximately 20 to 1,000. Number of live births in 1970then 7/1,000 Number of live births in 2000then 5.6/1,000 Number of births in 2022.
It’s still too expensive — Europe is doing better — but for about 15 out of 1,000 families who might otherwise have lost a child, this is a huge way the world is much better off than it was 50 years ago. Our progress in detecting and treating SCID, in particular, is such a rare disease that it is underrepresented in overall mortality statistics. many other rare diseases — Not to mention how much we did Improving care for premature babies.
Despite our fears, we are very grateful for the SCID test, which turned out to be unnecessary for our baby. For every dozen families like us who spent weeks worrying but turned out okay, there is another family who knew their baby was sick and was able to save their baby.
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