Early autism-specific observational and structured interview tools (eg, Childhood Autism Rating Scale,21 Autism Diagnostic Interview [ADI],22 and Autistic Diagnostic Observation Schedule)23 emerged from a need for standardized diagnostic instruments that were comparable and reproducible.24 But because these tools were highly specific and initially studied in research settings with high-risk populations, they lacked the sensitivity to identify children at risk in the general population, particularly those with milder symptoms.
As the diagnosis of autism became more standardized following publication of the DSM III-R in 1987, developmental specialists were able to construct increasingly sensitive evaluation tools. The ADI was revised25 to facilitate earlier and more efficient diagnosis, allowing for assessment of children as young as 19 months of age. The Checklist for Autism in Toddlers (CHAT)26 and subsequent modification (M-CHAT)27 were among the earliest and most effective screening tools, appropriate for use in children as young as 16 months old.
Tools that followed the original CHAT (eg, the Autism Spectrum Screening Questionnaire [ASSQ]28) were adapted to better identify high-functioning children with Asperger syndrome, as well as those with autism.
Another revision of the M-CHAT—the M-CHAT-R/F (Revised with Follow-up) was validated earlier this year. In a study involving 16,000 children, 95% of those who had positive tests were found to have some form of developmental delay and almost half (47%) received an ASD diagnosis.29
Other diagnostic aids are being explored as a means of promoting earlier identification of ASD. For example, a blood test to identify differences in gene expression between children with and without ASD30 has shown initial promise, particularly in males. This test is licensed by SynapDx (Lexington, Mass) and a clinical trial to evaluate it has begun.
Results of another study demonstrating normalization of brain activity in autistic children after they’ve undergone intensive treatment31 raise the possibility of using cortical activation as measured by electroencephalography as an early biomarker for autism.
Treatment options, advocacy affect rate of diagnosis
Improvements in diagnosis and targeted identification of potentially treatable symptoms32 led to the development of new treatment options. And greater use of day care and preschool programs prompted networking among parents, who touted the benefits of early evaluation, diagnosis, and treatment. Earlier screening, not surprisingly, led to an increase in the target population.
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Local as well as national advocacy groups, led primarily by parents, have become powerful voices for improvements in services offered to children with autism. And research studies with varying degrees of sophistication continue to be published, further fueling the demand for school systems to provide supportive learning environments as required by the Individuals with Disabilities Education Act, initially enacted in 1975 and amended in 2004.33
Federal and state funds in the form of Medicaid waivers are available to provide long-term care services in home and community settings, while private insurers typically pay for associated treatment modalities for those with an autism diagnosis, including physical, occupational, and speech therapy, among other services.
Finally, politicians and celebrities with personal connections to autism have joined the effort to increase awareness and improve the quality and availability of services—further assuring that autism is recognized as a legitimate, definable, and treatable disorder.
As an autism diagnosis has become more socially acceptable, it has at times replaced diagnoses of learning disability and mental retardation, a trend known as “diagnostic substitution.”34 Indeed, having a child with an ASD diagnosis often makes it possible for parents to secure services that might otherwise be unavailable to them.
Is the incidence of autism linked to the environment?
Numerous environmental, nutritional, and pharmaceutical changes have been cited as reasons for what is perceived as an increasing incidence of autism in recent years. For example, some contend that greater use of food preservatives and greater exposure of young children to environmental toxins are contributing factors.35
Thimerosal. Perhaps most notable is the assertion—since disproven—that thimerosal, a substance previously used in the manufacture of several childhood vaccines, was a leading cause of autism.36,37 In fact, one study documented an increase in autism after thimerosal had been discontinued.38 (For more on the thimerosal controversy, see “Autism: 5 misconceptions that can complicate care”.)