Doubts raised about U.S. autism estimates

Researchers are questioning the federal government's estimates regarding the prevalence of autism spectrum disorder in U.S. children, contending that the method used to assess the condition may have led to a significant number of false positives or cases where a diagnosis was missed.

Statistics released by the Centers for Disease Control and Prevention last March estimated that one out of every 68 children in the U.S. were living with autism, which constituted a nearly 30% increase compared with 2012 figures.

The estimates were based on the collection of medical records of 8-year-olds in 11 U.S. states in 2010. A review of those records plus an examination of education records provides a determination of whether a child may be autistic. But in an editorial published this month in the journal Autism, researchers contend this method of identifying the disorder relies solely on the validity of the observations made by clinicians and educators to gauge the indicators of the condition, and is not based on the government health officials' own health assessment of the children studied.

“We agree these are likely sources of these observed differences,” the article states. “But if they are, then these studies are not measuring true prevalence and should not be advertised as such. They instead measure the extent to which clinicians and educators test for and document the symptoms of autism, regardless of whether the practitioner ultimately assigns that diagnosis.”

Researchers argue that the varied array of results found throughout each state was further reason for concern over the CDC's assessment methods. The CDC's report found autism to be nearly five times more common in boys, of whom 1 in every 42 had an ASD diagnosis, compared to 1 in every 189 girls, and that the condition was found to be more prevalent in white children than black or Hispanic children.

The prevalence of ASD ranged widely from 1 in 45 children in New Jersey to 1 in 175 in Alabama. “Simply put, without direct assessments of children, we will not know the extent to which the CDC-determined 'cases' include false positives, or the extent to which children who it was determined do not have autism are really false negatives,” researchers wrote.

In response to the criticism, the CDC wrote in an e-mail to Modern Healthcare that the agency was “committed to scientific integrity and a high standard of quality for the autism data” that it reports, adding that there were different methods for estimating autism and that each method had its own “strengths and limitations.”

“CDC stands behind the ADDM (Autism and Developmental Disabilities Monitoring) Network's autism tracking method for providing the most complete picture of autism in communities across the United States,” the agency wrote.

Follow Steven Ross Johnson on Twitter: @MHsjohnson