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 (Casey et al., 2013). The flaws in this methodology certainly could explain the great variation in prevalence, clinical presentation, and racial disparities by site.
Tracking ASD is no easy task. In addition to the changes in diagnostic criteria, ASD is clinically complex and has no established biomarkers (Lai et al., 2014). The CDC surveillance studies have resulted in rich datasets from which much important research has been published regarding disparities in diagnosis (Giarelli et al., 2010;Mandell et al., 2009), age of diagnosis (Shattuck et al., 2009), and clinical presentation (Maenner et al., 2013). We question, however, whether they should be used any longer to provide meaningful estimates of prevalence. In fact, we believe it is a mistake to do so.