Correction: In a previous version of this story, the Journal of Pediatrics link led to an unrelated study. The link has been updated to point to the Journal of Pediatrics study.

Pediatricians could diagnose children with autism earlier by asking parents to fill out a simple, five-minute checklist when they take their babies in for their first-year checkups, according to research released Thursday.

The federally funded study involving more than 10,000 infants found that the questionnaire appeared to identify about half of children who eventually would be diagnosed with the brain disorder.

Early diagnosis would allow doctors to treat children with autism sooner, when therapy appears to be much more effective. By allowing scientists to study children with autism when they are younger, it could also provide crucial new insights into the disease’s causes, further dispelling discredited theories about vaccines and other supposed risk factors, as well as leading to better ways to diagnose and treat the disorder.

“This study is enormously important from the practical standpoint of helping families out,” said Karen Pierce of the University of California at San Diego, who led the research. “And from a scientific standpoint, it is undeniably important because for the first time you can study autism before the full-blown symptoms come on line.”

More than 36,000 children are diagnosed each year in the United States with autism spectrum disorder, a condition marked by social, communication and behavioral problems. Most are not identified until about age 5. Researchers have been trying to find the signs in younger children in order to start intensive therapy sooner and try to minimize abnormal behaviors.

In the new study, published in the Journal of Pediatrics , Pierce and her colleagues recruited 137 pediatricians in San Diego County to ask all parents of 1-year-olds coming in for well-baby check-ups to fill out the 24-item questionnaire while in the waiting room. The checklist was originally developed to identify language and developmental delays by asking parents questions about subtle variations in their child’s gaze, sounds, words, gestures and other behaviors.

Out of 10,479 infants who were screened between 2005 and 2009, 184 were referred for more specialized testing based on the results. Of those, 37 were diagnosed with autism. After following the children for about three more years, the researchers found that 32 still met the criteria for autism.

Because autism occurs in about 65 out of every 10,000 children, Pierce said, the results indicate that the screening can catch about half of children with autism. While that is far from perfect, it is much better than what usually happens, she said.

“Half is better than none. Most pediatricians still aren’t doing any screening,” Pierce said. “With this, you can detect cases of autism and other disorders and get these children into early treatment. If you catch these kids at 12 months, who knows what a huge positive impact that’s going to have on that child and the family and society at large?”

Overall, the screening tool was about 75 percent accurate at picking up autism or some other kind of developmental delay.

Other experts said that the findings were very promising.

“Beyond this exciting proof of concept, such a screening program would answer parents’ concerns . . . with more confidence than has ever been done before,” said Thomas R. Insel of the National Institute of Mental Health, which funded the study.

Advocates for families said better testing could help many parents, who often suspect their child may have autism years before receiving an official diagnosis. A reliable method to diagnosing autism earlier would ease unfounded fears or confirm well-founded suspicions.

“Too often parent concerns are brushed aside by pediatricians,” said Wendy Fournier, president of the National Autism Association. “Any tool that can help doctors recognize signs of developmental delays and get children access to early intervention services should be implemented.”

Other research has shown that intensively engaging children suspected of having autism in various ways, such as repeatedly prompting them to make eye contact with other people, can help ameliorate the symptoms.

Some experts, while praising the study and agreeing the approach was promising, said more research is needed before recommending routine use of the questionnaire.

“Given the negative implications if parents and pediatricians find a screening isn’t effective, what about a replication of this study somewhere” else, said Catherine Lord of the University of Michigan.

Pierce and others said the approach would only be useful in areas where parents have access to specialized testing centers in which children could undergo further testing to confirm a diagnosis and get appropriate treatment.

“Screening is only effective and ethical if you have someplace to send a parent,” Pierce said. “The downside would be stress on the family knowing there might be a concern and not really have an opportunity to get the child into treatment.”