PCR testing for congenital CMV produces ‘delightfully surprising’ results
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Key takeaways:
- University CMV testing among newborns is not common.
- In Minnesota, the first state with universal CMV testing, a study showed how well it works.
PCR testing of dried blood spots demonstrated a high sensitivity to identify infants with congenital cytomegalovirus in a study conducted in Minnesota, the first state to mandate congenital CMV testing, researchers reported at IDWeek.
According to the CDC, approximately one out of every 200 babies born in the United States has congenital CMV (cCMV), and around 20% of them will develop symptoms or long-term health issues like hearing loss. The virus is the leading cause of birth defects in the country.
Experts have advocated for universal newborn screening for CMV. In February, Minnesota became the first state to require it.
“Most babies with CMV do pretty well, but ... you never know,” Mark R. Schleiss, MD, a professor of pediatrics at the University of Minnesota, told Healio. “This is an infection worth detecting in every baby if it's present.”
Schleiss said a study conducted in the early 2000s showed that testing dried blood spots (DBS) from newborns was not effective at identifying cCMV.
“Beginning [about a decade ago] the molecular techniques to recover DNA became better,” Schleiss said. “So, I thought, well, we have to look at this again, because [if] you can find this infection by testing that blood spot that is being collected on every newborn anyway, then that's much more convenient and cost effective and efficient. We took another look at the question to see if we could do better than people have done in the past.”
The goal is to identify infants with CMV early and be able offer them interventions, Schleiss said.
“Too many times over the years, I've seen toddlers come in developmentally delayed — they have hearing loss, they're impaired, they have a lot of disabilities — and I think to myself, ‘I wish we'd known that at birth because then we could have helped this baby from the beginning,’” he said.
Schleiss and colleagues at University of Minnesota and CDC labs used PCR tests to screen for cCMV among 23,644 neonates at six newborn nurseries in Minnesota. They compared a PCR of saliva with a PCR of DBS obtained for routine newborn screening.
“Congenital CMV is a DNA virus, and so it's quite amenable to detection using the PCR technique,” Schleiss said.
Among newborns screened from February 2016 to January 2023, 3.7 per 1,000 had cCMV, the researchers reported. They calculated the analytical sensitivity — whether PCR could identify an infection — of saliva to be 93.1%. For DBS, it was 73.6% according to tests done at the University of Minnesota lab and 77% according to testing at the CDC lab.
The clinical sensitivity of PCR testing — its ability to identify CMV disease — was higher: 95% for saliva and 75% and 85% for DBS at the University of Minnesota and CDC lab, respectively.
The results were “delightfully surprising,” according to Schleiss, who said the method “worked better even than we would have predicted.”
“Going in, we didn't really know what to expect,” Schleiss said. “We had a hypothesis, a notion, an idea that that we would do better than other studies have done in the past because of better technical advances in the field, but I think we were all a little surprised at how well it worked.”
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Schleiss MR, et al. Abstract 968. Presented at: IDWeek; Oct. 11-15, 2023; Boston.
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