New research provides further evidence that some babies who pass their newborn hearing tests are found to be deaf or hard of hearing as young kids.

Some of those newborns may receive passing grades incorrectly, researchers said, but others can be born with good hearing but develop progressive hearing loss as babies and toddlers.

"A parent or a physician may think, ‘Oh, this child had passed the screen, so they must not have hearing loss,'" said Dr. David Chi, the study's lead author from the University of Pittsburgh Medical Center in Pennsylvania.

"Don't depend on just the fact that (your child) passed the screen, especially if there are any concerns about hearing loss or speech concerns," he told Reuters Health.

Chi and his colleagues analyzed the medical records of 923 kids who came to their medical center with hearing loss between 2001 and 2011, and were between four and five years old, on average. The children included 78 who had passed their initial newborn screening.

Of those kids, 28 were brought in because of parents' concerns about their hearing and 25 had failed school hearing tests, according to the findings published Thursday in JAMA Otolaryngology-Head and Neck Surgery.

There was no identifiable cause of hearing problems in more than half of the kids' medical records. The rest had deafness related to genetics, structural problems with their ears or complications from childhood such as infection.

It wasn't clear how long those kids had been hard of hearing before they were brought in and diagnosed.

"We don't know, ‘what is the false negative rate (of newborn screening) versus the delayed onset rate?'" said Dr. Nancy Young, a pediatric otolaryngologist from Lurie Children's Hospital of Chicago and the Northwestern University Feinberg School of Medicine.

Either way, she told Reuters Health, parents shouldn't be "falsely reassured" by their child having passed the newborn screening if they notice problems with the child's hearing or language.

Having deafness spotted and treated early, such as with cochlear implants, is important for children's future language development, she noted.

"We need to stay on the lookout and be vigilant and refer these children in," said Young, who wasn't involved in the new research.

Two or three out of every 1,000 U.S. children are born deaf or with hearing problems, according to the National Institutes of Health, and more go on to become hard of hearing.

The U.S. Preventive Services Task Force, a government-backed panel, recommends screening all newborns for hearing loss, based on "at least fair evidence" that the benefits of screening outweigh any possible harms.

Universal newborn hearing screening was instituted in Pennsylvania in 2001. Before that, hearing loss was typically diagnosed at around 26 months and hearing aids implemented at 30 months, Chi's team notes in its report. Since universal screening, interventions happen much earlier, by about six months of age.

Chi told Reuters Health that he and his colleagues are looking into strategies for screening young kids after the initial newborn test, such as with a second round of screening at three months of age.

But Young cautioned against going forward with such a plan until researchers have a better idea of when hearing loss is actually occurring for kids who pass their newborn tests but end up having problems.

"If a lot of this is driven by poorly done testing (and) equipment issues, then the focus should be on improving our current program, not on finding another time to screen," she explained.

"This paper is wonderful in raising awareness of the shortcomings of newborn hearing screening, but I really think we need to take it to another level to sort out, who are these children, and why did they pass?"