PCR-based saliva test can accurately identify cytomegalovirus infection in newborns

Although cytomegalovirus infection is a known cause of birth defects, including permanent hearing loss, most CMV infections in infants are not identified early, when interventions can lessen the effects of hearing loss.

Now, Suresh Boppana, M.D., and Karen Fowler, Dr.P.H., from the University of Alabama at Birmingham and colleagues from other academic medical centers report that a polymerase chain-reaction (PCR)-based saliva test can identify CMV in newborns with greater than 97 percent accuracy. The traditional testing method, a "rapid culture" saliva test, is also accurate, but Boppana says it is not feasible to screen a large number of babies because of its expense, the time it takes for results and the requirement for a tissue culture facility.

The findings from their multi-center study will be published in the June 2, 2011, issue of the New England Journal of Medicine.

"Our objective was to find what method could test for CMV in a larger sample, rapidly, reliably and relatively inexpensively, we found that testing saliva works well," says Boppana, a professor of Pediatric Infectious Diseases and the paper's corresponding author.

According to the Centers for Disease Control and Prevention, one in 150 babies will be born with CMV. "When you look at babies in the nursery, you don't even know which ones are infected; they're like any other baby in there," Boppana says.

There is currently no cure for CMV infection or even a clear connection between CMV and hearing loss. But Boppana says babies should still be tested within the first two to three weeks of birth. The sooner doctors know a baby is infected with CMV, the better they can monitor and intervene if a child develops hearing loss. Those interventions include speech therapy, hearing aids, cochlear implants and physical therapy.

CMV is the most common infection passed from a mother to her unborn child, and there is no vaccine for it. "If a pregnant woman acquires CMV for the first time during pregnancy, then the chances of her passing it on to the baby are 30 to 60 percent," Boppana says.

Fowler says there are a variety of ways that a mother can contract CMV.

"Often mothers get the virus through exposure to young children — children in the household or their friends' children or children who have been in day care. But CMV also can be transmitted between adults sexually," says Fowler, also a professor of Pediatric Infectious Diseases.