CLOSER SCRUTINY OF THE AUTISM EPIDEMIC

Background: Much attention has been paid to the recent CDC report suggesting an increase in the incidence of autism spectrum disorders (ASDs).  Recent data suggest that, in California, causes are unlikely to be solely environmental (Schechter and Grether, 2008).  However, it remains unclear whether this change in incidence reflects a true increase in the number of children meeting DSM-IV criteria for autistic disorder (AD) or is an epidemiologic confound. Objectives: Children reported by their parents to have a diagnosis of an ASD were evaluated to determine whether this diagnosis withstood further scrutiny.  This set of patients included children whose parents suspected that their child had autism based on their own research and gave a positive history during a screening interview, as well as children diagnosed with an ASD by non-ASD specialist clinicians or by the educational system.
Methods: Children (N=190) who presented for diagnostic evaluation were assessed using the DSM-IV diagnostic criteria for AD, ascertained using methods consistent with the California Department of Developmental Services Best Practices Standards (CA DDS, 2002).  Results: Only 51% of children with referral diagnoses of AD (N=90) received confirmation of AD following assessment.  The 49% of children who were not confirmed to have AD received either a different Axis I diagnosis (22% had an ASD but not AD and 20% had a non-ASD diagnosis) or were found to have no Axis I diagnosis (7%). Conclusions: A large fraction of the children previously viewed as having AD did not meet DSM-IV criteria for AD when re-evaluated using methods focused on raising convergent validity. Thus, in the referral population we sampled, diagnostic errors are likely introduced from various sources.  These sources, including media foment and non-specialist diagnosis without best-practices standards, can yield a different diagnostic impression of AD than a diagnosis derived from a standardized, best-practices assessment.