One of the big topics of discussion in the past few years was the roll out of the DSM-5. The new criteria for what defines autism. One could find those saying “this is designed to undiagnose autistics with intellectual disability” as well as “this is designed to undiagnose autistics without intellectual disability” together with the multiple comments that “this is designed to obfuscate the “epidemic” of autism”.
A recent paper discusses this: Potential Impact of DSM-5 Criteria on Autism Spectrum Disorder Prevalence Estimates. The study looks at the CDC’s ADDM network–the same basis for the CDC autism prevalence estimates that come out every two years.