Although autism can be reliably diagnosed as early as 2 years of age, many children are not diagnosed with autism until much later. We analyzed data to determine why many of the 8-year-old children who resided in Colorado and were identified as having autism through a review of their health and/or educational records did not have a documented clinical diagnosis of autism and were not eligible for special education services under an autism eligibility. We found that children who did not have a documented clinical diagnosis of autism and were not eligible for special education services under an autism eligibility were more likely to be female, aggressive, and argumentative. They had a poorer quality of information in their records and were less likely to have had a developmental regression, sleep problems, or an autism screener or diagnostic measure in their records. These results suggest that the symptoms characteristic of autism among this group of children may have been attributed to another disorder and that clinicians may be able to recognize autism more readily in children with more functional impairment and those who experience a developmental regression. We also discovered that differences in symptom presentations among children who had a documented clinical diagnosis of autism and/or were eligible for special education services under an autism eligibility were associated with different ages at autism diagnosis.
Keywords: autism spectrum disorder; early diagnosis; health disparities; missed diagnosis.