New York - Most children diagnosed with autism at two years of age will still have that diagnosis at age nine, investigators report.
In contrast, many young children first diagnosed with less severe conditions - called pervasive developmental disorder not otherwise specified (PDD-NOS) and autism spectrum disorder (ASD) - later have their diagnoses changed to autism.
Dr Catherine Lord, from the University of Michigan Autism and Communication Disorders Center in Ann Arbor, and her associates report that clinicians have been questioning the stability of these diagnoses.
The researchers therefore followed 192 children referred for evaluation for possible autism before 36 months of age, plus 22 children with developmental delays between ages 13 and 35 months. At age 9, 172 of these children were available for re-evaluation.
According to their report in the Archives of General Psychiatry, the researchers found that at age nine, most of the changes in diagnosis were "associated with increasing certainty of classifications moving from ASD/PDD-NOS to autism".
More than half of those initially diagnosed with PDD-NOS later met the criteria for autism, Lord's team indicates. Conversely, only one of 84 children diagnosed with autism at age two years was found to not have the condition at nine years of age.
The researchers comment that, since more than half of those first diagnosed with PDD-NOS later were characterised as autistic, "health care professionals should be wary of telling parents that their young children do not have autism."
SOURCE: Archives of General Psychiatry, June 2006.