Received a Positive Newborn Screening Test? It May Be A False-Positive!

Last Updated: Dec 21, 2023

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To prepare ourselves for the arrival of our daughter (our first child), my wife and I took a few baby and parenting classes. We read books on the subject, and we researched on the internet.

What we discovered is that the amount of information (and misinformation) available to new parents today is overwhelming. So we had to be selective and hence didn’t pay too much attention to “stuff that could go wrong,” such as diseases and complications.

With no family history of major disorders or genetic defects, we figured the chances were good that everything would be just fine.

But we did become aware of common procedures for newborns such as:

  • Newborn hearing tests (to make sure the baby’s hearing is OK, which is important for speech development).
  • Newborn screening tests (to catch genetic or metabolic diseases early).
  • Vitamin K shots (to help with blood clotting until the baby’s own Vitamin K production kicks in).
  • Antibiotic eye ointment (to prevent infection caused by bacteria in the birth canal).
  • Initial assessment of the baby’s vital functions at 1 minute and 5 minutes after birth.

We also knew to be on the lookout for:

  • Elevated bilirubin levels (Jaundice or yellow coloring of the skin caused by immature liver).
  • Other minor skin defects (pimples, spots, etc.).
  • Hair growth on body parts other than head (this is called lanugo, is completely normal, and disappears after a few weeks).
  • Enlarged genitalia (due to the mother’s hormones being passed on to the baby).

Of course, every time I read something like, “Some babies may have XYZ condition,” I naturally assumed that would only to other babies, not ours.

The Standard Newborn Screening Test

According to Baby’s First Test:

“Newborn screening is a state public health service that reaches each of the more than 4 million babies born in the United States every year. It ensures that all babies are screened for certain serious conditions at birth, and for those babies with the conditions, it allows doctors to start treatment before some of the harmful effects happen.

Newborn screening is performed soon after the birth of your baby, and in most cases, while you are still in the hospital. All it takes is a few drops of blood and a simple hearing test.”

— “Newborn Screening 101”

Then, in the book “Baby 411: Clear Answers & Smart Advice For Your Baby’s First Year,” we read that a pediatrician is unlikely to discuss the test results unless at least one of the tests is positive. So we expected not to hear anything about our newborn screening after our baby’s blood was drawn at the hospital, one day after birth.

After all, we assumed that everything would be fine.

During the first week of our daughter’s life, we had appointments with our pediatricians, Dr. Michael Papciak and Dr. Rebecca Clements of Preston Ridge Pediatrics (who I highly recommend), almost every day for checkups. In particular, we were checking to make sure her weight was increasing and her bilirubin levels were decreasing.

Jaundice is caused by elevated bilirubin levels and causes newborns to be sleepier than usual, so they may not eat as much as they should.

Fortunately, both checks went according to plan. But on Day 10, our pediatricians ordered an extra blood test and a second newborn screening test. They told us not to worry, but explained that one of the newborn screening tests was positive.

More specifically, we were told that our daughter’s 17-OHP levels were elevated, which caused a test for Congenital Adrenal Hyperplasia (CAH) to come back positive.


Congenital Adrenal Hyperplasia

I had never heard CAH, and I asked Dr. Papciak for a copy of the test report so I could do some research. We were still at the the doctors’ office when I googled for CAH. The first hit was this Wikipedia article that summarized CAH as follows:

“Congenital adrenal hyperplasia (CAH) refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands (steroidogenesis).
Most of these conditions involve excessive or deficient production of sex steroids and can alter development of primary or secondary sex characteristics in some affected infants, children, or adults.”

— Wikipedia

When I read “a genetic disorder involving sex steroids resulting in potentially altered sex characteristics,” I felt like I had been hit by a train. And I wasn’t sure how to tell my wife what I had just learned.

Back at home, I started doing some more research and learned that the most common form of CAH is caused by a deficiency in an enzyme called 21-hydroxylase. Within this particular form there are three different types of CAH, which vary by severity level:

Salt-Wasting CAH (Classic Form).

This is the most severe and common form (75% of patients affected by 21-hydroxylase deficiency have this form). It can lead to death within weeks, caused by the body excessively wasting certain electrolytes. That’s why our pediatrician had our daughter’s potassium and sodium levels tested right away. Since the levels were normal and she didn’t show any of the other symptoms (such as vomiting and lethargy) we concluded that she was probably not suffering from this form of CAH.

Simple Virilizing CAH (Classic Form).

This form of CAH is less severe and typically manifests in ambiguous genitalia (i.e., girls may have an enlarged clitoris that looks like a penis), excessive hair growth, etc. Despite not being life-threatening, it can lead to accelerated growth. But since the epiphyses fuse early, affected patients are often of a short stature. It can also cause infertility and other issues.

We were told in the hospital, as well as by our pediatrician, that our daughter was physically OK (i.e., no penis and normal hair growth). But given the positive newborn screening test, I couldn’t help but relate the hair on her back (lanugo) and her slightly enlarged genitalia (normal for a newborn) to CAH.

I even read a study called “Penile and Clitoral Sizes of Normal Full-Term Newborns in Korea” to make sure our daughter’s genitalia was within the normal range. It turned out to be within normal range, which meant she could only have a very mild form of Simple Virilizing CAH, if at all.

Late-Onset CAH (Non-Classic Form).

Late-onset CAH is the mildest form of CAH. And as the name implies, it manifests later in development and doesn’t necessarily and/or immediately affect newborns.

The more research I did, the more it became clear that reliable testing for CAH in newborns is not a simple task, and that the false-positive rate is quite high.

Even Baby’s First Test points out the following:

“It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition

Dr. Philip M. Farrell, a professor of pediatrics and population health sciences at the University of Wisconsin School of Medicine and Public Health, estimated that 1 in 50 newborn screening tests are false-positives. But for CAH, there are between 100 and 200 false positives for every child truly affected.”

That’s a very high false-positive rate, and it gave us hope that our daughter’s test could also be a false-positive.

To get more information about test procedures in Georgia, I sent an email to Joanna Pringle, a program consultant at the Newborn Screening Unit of the Georgia Department of Public Health. She called me back within a few hours, and also forwarded my email to Angela Wittenauer, a registered nurse at the Genetics Lab of Emory University. She too called me back and confirmed that there are many false-positives and that there was no need to be worried.

We just needed to wait for the results of the second test.

Our Baby’s Negative Test Result

About two weeks after the pediatrician sent in the blood sample for the second test, we got the good news that it was negative and hence the first test was a false-positive caused by high cortisol levels in our daughter’s bloodstream a day after birth.

The elevated cortisol levels were most likely caused by the stress of being born.

Who knew that the delivery process was as stressful for the baby as for the parents!

Bottom line: Every newborn is different, and a positive newborn screening or a failed hearing test may not mean anything. So stay calm, enjoy the nightly feedings and diaper changes, and wait for the second test before freaking out.

Medical Disclaimer

The information shared on this blog is for educational purposes only, is not a substitute for the advice of medical doctors or registered dieticians (which we are not) and should not be used to prevent, diagnose, or treat any condition. Consult with a physician before starting a fitness regimen, adding supplements to your diet, or making other changes that may affect your medications, treatment plan or overall health. MichaelKummer.com and its owner MK Media Group, LLC are not liable for how you use and implement the information shared here, which is based on the opinions of the authors formed after engaging in personal use and research. We recommend products, services, or programs and are sometimes compensated for doing so as affiliates. Please read our Terms and Conditions for further information, including our privacy policy.

10 thoughts on “Received a Positive Newborn Screening Test? It May Be A False-Positive!”

  1. Thanks for sharing this! We just got the call from the pediatrician that our 2,5 week old needs to be re-tested for PKU disorder :( Im devastated and cant keep myself from thinking about what this disorder would do to our seemingly perfect little girl. I pray it turns out to be a false positive!

  2. After I was called and informed my little one tested positive for Biotinidase deficiency just 5 days into her new life…. my heart dropped and I just wanted to crawl in a hole. So much went through my mind and trying to cope with a newborn as first time parents. I ended up researching and learning so much about this disorder that most doctors who practice 45 years never came across. I knew more about it then any doctor I spoke to. We were told to bring the little one to have her tested to confirm at Sick Kids in Toronto. The results will come in 2 weeks. The wait in those two weeks was stressful. Little redness or spots on the baby had me going nuts…. thinking it is signs and symptoms. Finally the test results came back and my little one was a false positive. No further follow up needed and instantly discharged by Sick Kids. I felt like I won the lottery. So for any parent who gets this positive screen call…. I know what you are going through. I did a lot of reading online and the confirmed case for all those positive calls are extremely low. Like Biotinidase which was my case. 5000 positive screen and only 32 were confirmed. You still have the odd ironically. Hope my stories help shine some hope for those going through this.

  3. We have almost the same experience when my daughter was screened! My LO is a preemie. Initially, tested positive for CAH but after 2 more repeat NBS she tested negative. It was really heart-breaking and i spent hours of searching about CAH. Thank God all is well…

  4. Thanks for writing this. It’s nice to ready about someone else going through the same thing! We just had our little boy’s retest done today. Hopefully it will be negative. He had an extra stressful birth (shoulder dystocia) so hoping that’s the reason for his positive result!

  5. Thank you for sharing this. I as well got positive results for this condition on my daughters labs but I’m very confused as she doesn’t have any of the symptoms? I’m so heartbroken. Today we had her second newborn screening sent off to the lab … Im really beside myself.

  6. Omg, this is exactly what I went through all day yesterday! I was told my preemie baby girl was positive for CAH. I googled and tried to find anything I could on it and searched for images to compare her to and was driving myself insane! I felt so many emotions and later I was told by the dr. not to worry because it was very common for preemie babies to have abnormal newborn screenings as you said. But, I’m glad I found this so I know I’m not a crazy overreacting parent! I knew it would be hard but man is this a roller coaster!!

  7. I’m waiting for the results of the second screen after my baby got a borderline positive on the first test?.He seems so healthy I’m just praying that it was a false positive.???

  8. Thank you so much for writing this. I’m waiting for the results of the second screen after my baby got a borderline positive on the first test. He seems so healthy I’m just praying that it was a false positive. They need to work on improving the ppv of these tests. It’s so hard on new moms!!!


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