Spotting newborns at risk of hearing loss

A simple DNA test of saliva from a newborn can reveal whether the baby has a viral infection that can cause deafness in some cases. The DNA test is simpler and faster than the assay currently available and catches more than 97 percent of such infections, researchers report in the June 2 New England Journal of Medicine.

“This is really exciting,” says Elizabeth Stehel, a pediatrician at the University of Texas Southwestern Medical Center at Dallas, who wasn’t involved in the study. Such a test “would fill the need that many people feel we have — to screen babies to detect a virus that contributes to so much hearing loss.”

Cytomegalovirus is in the herpes virus family. Although it is common in the population and typically innocuous, cytomegalovirus can be dangerous to babies born with the infection, causing hearing loss in 10 to 15 percent of infected newborns. It is among the leading causes of deafness in children.

Hospitals can spot some cytomegalovirus infections, particularly those that cause severe disabilities. Doctors routinely test all newborns for genetic conditions such as sickle cell disease by sending dried blood samples to a state’s central laboratory. Yet few hospitals test for congenital cytomegalovirus in babies who appear healthy, even though it is present in about 0.5 to 1 percent of such newborns.

Researchers at the University of Alabama at Birmingham recently found that blood tests of newborns often can’t predict whether the child is infected with the virus. Cytomegalovirus apparently doesn’t always get into the bloodstream in newborns, says Suresh Boppana, a pediatrician and infectious disease researcher at the UAB School of Medicine.

But it does show up reliably in saliva. In the new study, Boppana and colleagues at seven U.S. hospitals double-tested saliva from more than 17,000 newborns in 2008 and 2009, nearly all of whom appeared healthy. The scientists compared the DNA test against a standard test in which saliva is placed on cells grown in a lab. The cells are then exposed to an antibody that reacts to cytomegalovirus. The DNA test detected all 85 virus-positive cases that were also caught by the standard test, with only a handful of false-positive findings.

The researchers then repeated the test on another 17,000-plus newborns, this time using dried saliva samples. Of infections detected by the standard test, the DNA assay spotted more than 97 percent, again with few false positives.

“This saliva test is simple, it appears to be cost-effective and … reliable,” says geneticist Bracie Watson at the National Institute on Deafness and Other Communication Disorders, in Rockville, Md., which funded the study. The researchers are continuing the project, with the goal of testing 100,000 newborns.

Screening for cytomegalovirus in newborns “is hardly ever done,” Boppana says. “I think this [DNA test] could be further automated so you could screen large numbers of babies.” For that to begin, public health regulators at the federal level would need to endorse the idea, he says.

Drugs to treat cytomegalovirus infection in newborns are still in the testing stage as is a vaccine against the virus (SN: 4/29/09, p. 11 ). And although all newborns are checked for deafness at birth, a silent infection with cytomegalovirus can cause hearing loss months or years later, Stehel says. 

Boppana adds, “The sooner you detect hearing loss, the sooner you can intervene.” Hearing aids and cochlear implants at an early age can preserve an infant’s ability to develop speech, he says.