NEW YORK -- A government survey of parents says 1 in 50 U.S. schoolchildren has autism, surpassing another federal estimate for the disorder.

Health officials say the new number doesn't mean autism is occurring more often, but it does suggest that doctors are diagnosing autism more frequently, especially in children with milder problems.

The earlier government estimate of 1 in 88 comes from a study that many consider more rigorous. It looks at medical and school records instead of relying on parents.

"With regard to the 1 in 50 study, a survey of parents -- I believe that the input of parents is important. Parents know their children better than anyone in most cases and are first line advocates for care of their children," said Jenny Knoderer, executive director of the Tailor Institute in Cape Girardeau.

The Tailor Institute works primarily with teenagers and young adults with autism.

"We work to prepare them for life after high school, whatever that looks like relative to their specific situation, while focusing on their strengths and areas of giftedness as avenues for living independence," Knoderer said.

She added that the institute has launched its first children's program, a pilot program called Creative Minds, which offers services to children ages 6 to 12.

Change of definition

For decades, autism meant children with severe language, intellectual and social impairments and unusual, repetitious behaviors. The definition has gradually expanded and now includes milder, related conditions.

The new estimate released last month by the Centers for Disease Control and Prevention would mean at least 1 million children have autism.

The number is important -- government officials look at how common each illness or disorder is when weighing how to spend limited public health funds.

It's also controversial.

The new statistic comes from a national phone survey of more than 95,000 parents in 2011 and 2012. Less than a quarter of the parents contacted agreed to answer questions, and it's likely that those with autistic children were more interested than other parents in participating in a survey on children's health, CDC officials said.

Still, CDC officials believe the survey provides a valid snapshot of how many families are affected by autism, said Stephen Blumberg, the CDC report's lead author.

The study that came up with the 1-in-88 estimate had its own limitations. It focused on 14 states, only on children 8 years old, and the data came from 2008. Updated figures based on medical and school records are expected next year.

"We've been underestimating" how common autism is, said Michael Rosanoff of Autism Speaks, an advocacy group. He believes the figure is at least 1 in 50.

Detection

There are no blood or biologic tests for autism, so diagnosis is not an exact science. It's identified by making judgments about a child's behavior.

Doctors have been looking for autism at younger and younger ages, and experts have tended to believe most diagnoses are made in children by age 8.

However, the new study found significant proportions of children were diagnosed at older ages.

Dr. Roula Choueiri, a neurodevelopmental pediatrician at Tufts Medical Center in Boston, said she's seen that happening at her clinic. Those children "tend to be the mild ones, who may have had some speech delays, some social difficulties," she wrote in an email. But they have more problems as school becomes more demanding and social situations grow more complex, she added.

For more information on the Tailor Institute, call 339-9552 or visit www.thetailorinstitute.org. For more information on the Southeast Missouri State University Autism Center, call 986-4985 or visit www.semo.edu/autismcenter.

Assistant managing editor Lucas Presson contributed to this story.

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Online:

CDC report: http://www.cdc.gov/nchs/