That assessment is not a thumbs-down for universal screening to detect newborn hearing problems, says study leader Diane C. Thompson, an epidemiologist at the Harborview Injury Prevention and Research Center in Seattle. "We're concerned that the media will interpret our report to say we are not in favor of universal screening, and that is not true. It's just that the evidence to show whether universal screening can improve language skills for these children is not clear," she says.
Hearing loss affects about one of every 900 to 2,500 babies born in the United States, and about 5,000 infants are born with moderate to profound deafness every year. Because hearing during the first six months of life is critical to development of speech and language, 33 states now mandate hearing tests for all newborns. Ohio, where a screening bill is moving through the legislature, may soon become number 34.
With financing from the U. S. Preventive Task Force, a federal organization, Thompson and her colleagues looked at 340 scientific articles, selecting 19 that offered solid evidence about the value of universal screening in preventing language problems. Their findings appear in the Oct. 24/31 issue of The Journal of the American Medical Association.
One thing that quickly became evident is that today's tests are highly effective, Thompson says. "Modern hearing tests make it possible to screen newborns with high specificity and sensitivity," she says. "They've gotten better and better in the last five or six years."
One kind of test measures response to sound through a small probe inserted in a baby's ear canal. Another uses electrodes placed on the scalp to detect activity in the brain stem's auditory region. Both tests are at least 80 percent effective in detecting moderate hearing loss and at least 90 percent effective in detecting profound deafness, the journal report says.
But the kind of studies needed to provide definitive proof that early detection and treatment are effective haven't been done, Thompson says. "What you want is studies that follow these children and look at language outcome. No one has done that. That is the key bit of evidence that has to be provided."
Several studies showed that children whose hearing problems were diagnosed in the first six months of life had less severe language difficulties than those diagnosed after six months, Thompson says. But the selection of children for those studies and the methods of assessing their progress were imperfect, she says.
"None of the studies had clear criteria for inclusion, none had blinded assessments, and all selected children for inclusion on the availability of a language assessment between 2 and 5 years," and "this could introduce bias," the journal report says.
But Elizabeth Thorp, director of the National Campaign for Hearing Health, a private organization, hears a different message. "Regardless of hard evidence, it makes sense to have hearing screening done on every baby before he or she leaves the hospital. Early intervention is the key," Thorp says.
Hearing loss "is our nation's number one birth defect," she says, and the screening test is neither difficult nor expensive. "I've seen little babies getting these tests, and they're out cold or sucking their thumbs. The tests cost only $20 to $50, and many states pay for them," Thorp says.
Even a minor hearing problem can make life difficult, says Thorp, who has a hearing impairment that was not diagnosed until she was 8 years old. "If you have a 10 percent hearing loss, that means you hear only nine words out of 20," she says.
What To Do
Parents can judge a child's hearing by watching his or her reaction, Thorp says. Up to 3 months of age, watch whether the baby responds when spoken to by smiling or turning the head. From 3 to 6 months, see whether the baby responds to words such as "no" or looks upward and turns around in response to sounds.