of disorders on the autism spectrum or the result of better diagnoses and information availability; or, perhaps a combination of both.
With this background information, the Task Force then examined the available data for autism prevalence in Delaware. Its primary sources of information on Delaware were the Autism Registry, the Delaware Department of Education special education classification data, and finally, data from the Delaware Division of Developmental Disabilities Services (DDDS). (Appendix D)
Data on children with autism in the public schools in Delaware shows that as of 12/1/2007 there were 779 identified students ranging from age three to 21 with an educational classification of autism. Assuming a public school population of 160,000 students, this produces a ratio of approximately 4.9 per 1000 or 1 per 205 children as compared to the CDC data of a 1 per 150 children rate. Also, DDDS data shows that approximately 371 persons currently receiving services are identified as having a disability on the autism spectrum. Of this number, 207 are adults, with another 47 students between the ages of 18 and 20 who will enter the system in the coming two years, thus increasing the number of adults served by 18%. Assuming a Delaware population of 800,000, this produces a ratio that is well below the national averages. The Task Force believes there are several reasons for these discrepancies.
First, the Department of Education only began using a broader definition of autism that includes Asperger Syndrome and PDD-NOS as part of the definition of autism in the 2005-06 school years. It is likely that the practice of using a broader definition has probably not yet caught up with definitional changes so the Task Force believes that students with diagnoses of Asperger Syndrome, PDD-NOS and others who are not eligible for the DAP may not be captured in the data. In addition, the CDC study found that depending on the particular study site 30 to 70% of the children with a diagnosis of an autism spectrum disorder had a different special education classification (i.e. learning disability, emotionally disturbed, behavior disordered, etc.). Therefore, it is expected that there are a number of students with autism spectrum disorders who have other educational classifications.
Second, the DDDS data is very limited in its ability to project adult prevalence rates. DDDS services are voluntary and not mandatory as are educational services. Individuals and families may choose not to seek services from DDDS, feel they do not need state services, or obtain supports and services from the informal family, friends and community and faith based support networks outside the formal state network. In addition, DDDS eligibility criteria did not cover individuals with spectrum disorders unless the disorder was classic autism or autism accompanied by mental retardation and/or aggressive behaviors until the past few months. Few, if any, adults with higher functioning autism would be captured by their data. Also, most individuals served by DDDS are classified as having mental retardation rather than autism, so they may not be capturing all of the individuals they currently serve with the correct diagnosis.
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