They say to leave things up to the experts. In this case, the experts at detecting autism may be the parents. A new study from Brigham Young University finds more than a third of psychologists failed to recommend a referral on the grounds that they believed the child they were observing was autistic.

Autism rates in the U.S. are climbing in a hurry. In 2000, the Centers for Disease Control and Prevention estimated one in every 150 children fell somewhere on the autism spectrum. In 2010, that rate had jumped to one in 68. Science hasn’t been able to pin down a singular cause behind the swell, and it is beginning to doubt one cause exists at all. As the latest study suggests, for example, years of missed diagnosis may have artificially lowered the actual rate.

Parents aren’t necessarily experts for their special powers of observation, says the study's lead author and BYU assistant professor Terisa Gabrielsen. Doctors just can’t spend as much time with the kids as their parents. These difficulties often persist until the children reach school age, by which point they may already face certain social and academic challenges.

"One of the biggest problems with early identification of autism is that many children aren't identified until they reach the school system," said Gabrielsen in a statement. "This means that they have missed out on some prime years for intervention that can change a child's outcome."

Gabrielsen and several of her colleagues collected data on 42 children between 15 and 33 months old. Some of the kids were "typically developing controls" — in other words, mostly normal children — and others who had "screened positive during universal autism screening within a large community pediatric practice." A group of psychologists watched each child for a period of 10 to 20 minutes, assigned with the task of judging autism symptoms and signs for abnormal behavior. Specifically, they looked for five key factors: Responding, Initiating, Vocalizing, Play, and Response to Name.

To the researchers’ surprise, the psychologists’ performance wasn’t so hot; they missed autism cases in 39 percent of their referrals. However, they may not be entirely to blame. By the researchers’ own admission, kids in the autism group exhibited typical behavior 89 percent of the time. That is, they looked exactly like the normally developing kids nearly nine out of 10 times.

"It's often not the pediatrician's fault that referrals are missed," Gabrielsen said. Parents get to spend many hours each day with their child, and doctors get access to only a thin slice of that enormous pool of information. That’s why she and her team recommend more parent involvement in formal autism screening, in addition to the methods that are already in place. The American Academy of Pediatrics, for instance, recommends screening at 9, 18, and 24 months during regular check-ups. In between, parents can use the CDC’s “Learn the Signs. Act Early” campaign to stay informed.

As the CDC’s campaign title hints, autism as developmental disorder isn’t totally immune to early action. Younger brains are more “plastic” than older brains, which means thoughtful parents and doctors can take steps to minimize social and behavioral setbacks. These changes may not be life-altering — some research has found autism starts developing while children are still developing inside their mothers’ bellies, suggesting what’s done is done. On the other hand, many therapies have been met with success, particularly in the realm of social skills, which autism generally stunts.

"Parents see their children at their very best and very worst," Gabrielsen said. "They're the experts for their children. They can be educated about signs and symptoms, and need to help their care providers by speaking up if there's a problem and being involved in referral decisions."

Source: Gabrielsen T, Farley M, Speer L, Villalobos M, Baker C, Miller J. Identifying Autism in a Brief Observation. Pediatrics. 2015.