Saliva Tests for Infants May Identify Risk of Hearing Loss, Study Shows

June 2, 2011

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A simple saliva swab may help doctors better identify newborn babies born with an infection that is responsible for as much as 25 percent of hearing loss early in life, a study found.

The study, led by researchers from the University of Alabama at Birmingham, identified all babies infected with cytomegalovirus, or CMV, when using a wet saliva sample and about 97 percent when using a dried saliva sample. The research was published today in the New England Journal of Medicine.

One in 150 children born in the U.S., or about 30,000, are infected with CMV, the most common infection passed from mother to unborn child, according to the U.S. Centers for Disease Control and Prevention. About 10 percent to 15 percent of those will develop a disability such as hearing loss, said pediatrician and lead study author Suresh Boppana. While babies aren't currently screened for CMV, the study's findings could help make testing for the infection routine, he said.

"Most babies with CMV infection won't be identified at birth, unless you screen them for CMV infection, because they look like every other healthy baby," said Boppana, a professor of pediatrics at the University of Alabama at Birmingham in a May 31 telephone interview.

Studies estimate that about 20 percent of hearing loss at birth and 25 percent of hearing loss seen in 4-year-olds is due to CMV, Boppana said. A screening test for CMV would cost about $2.50 to $3, he said.

Understanding CMV

In a separate trial currently under way, researchers are following children with congenital CMV and monitoring their hearing every six months until they are 4 years old. Results from the study, designed to give doctors a better understanding of how CMV causes hearing loss, won't be available for several years, Boppana said.

"If our results confirm that congenital CMV is a major cause of hearing loss, then there's an impetus on the national agencies to think about considering making a recommendation that every baby needs to be tested for CMV," he said.

Researchers took saliva samples from almost 35,000 babies in seven U.S. hospitals from June 2008 to November 2009. Some of the saliva samples were stored in solution and some were air dried. The researchers then compared their results with another highly accurate test, called the rapid culture method, that isn't conducive for widespread use because it involves lengthy incubation and testing procedures.

Of 17,662 newborns screened with the saliva samples stored in solution, 85 were positive for CMV, a 100 percent match to the rapid culture method. Of 17,327 newborns screened by having their dried saliva tested, 74 were positive for CMV. The rapid culture method found 76.

"It's important for us to develop diagnostic tools to screen babies for congenital CMV infection so that those who test positive can be monitored for possible hearing loss and, if it occurs, provided with appropriate intervention as soon as possible," said James Battey Jr., director of the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health, which funded today's study, in a statement.