Researchers Question Autism Prevalence Rates From CDC
Earlier this year, the Centers for Disease Control and Prevention said that autism spectrum disorder was now found in 1 in 68 children, based on monitoring that the agency conducts in ten states.
The numbers marked an upward spike in autism prevalence: in 2008, the estimate was that approximately 1 in 88 children in the monitored states had been diagnosed with an ASD. In 2006 the ratio was 1 in 110, and in estimates for 2002 and 2000, it was 1 in 150.
But are these numbers accurate?
In the July issue of the journal Autism, the editors of the publication argue that the CDC numbers can't provide a meaningful estimate because they are based on a review of records for a child, not an independent assessment. The records themselves could be over- or understating the existence of a disorder because of local policies, resources and awareness, wrote David Mandell, a health services researcher and psychiatric epidemiologist at the Children's Hospital of Philadelphia, and Luc Lecavalier, a professor of psychology at Ohio State University in Columbus. They wrote:
In a "true" prevalence study, the information a child has in their clinical or educational record is irrelevant. Researchers identify some population or population-based sample and clinically assess individuals in person to determine the presence of ASD. The CDC did not rely on this in-person strategy, presumably because of the high costs. The result, however, is that the data they have collected may be uninterpretable as it relates to prevalence.
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. Social impairments and repetitive behaviors are present in many other childhood psychiatric disorders and developmental disabilities, The flaws in this methodology certainly could explain the great variation in prevalence, clinical presentation, and racial disparities by site.
In response, the CDC emailed Education Week a statement saying "there are different methods to estimate the number of children with autism, each with its strengths and limitations," and that it stands behind the numbers gathered from its monitoring network as providing the most complete picture of autism in communities across the country.
The agency also referred to a 2011 study that was published in the Journal of Autism and Developmental Disorders, that compared diagnosing autism by reviewing records to making the diagnosis after a clinical examination and found a close correlation in results, though that study also noted that relying solely on a records review likely yields a conservative estimate of how many children actually have the disorder.