We investigated the relationship between parent-reported assessments and autism spectrum disorder (ASD) severity level. Parents evaluated 9573 children with ASD on five subscales-combinatorial receptive language, expressive language, sociability, sensory awareness, and health-using the Autism Treatment Evaluation Checklist (ATEC) and Mental Synthesis Evaluation Checklist (MSEC). The scores in every subscale improved with age, and there were clear differences between the three diagnostic categories. The differences between mild and moderate ASD, and moderate and severe ASD reached statistical significance in each subscale and in every age group in children 3 years of age and older. These findings demonstrate a consistent relationship between children's diagnoses and their assessments and provide evidence in support of the reliability of parent-report evaluations for ASD. Additionally, this is the first investigation of the relationship between ASD severity level and the ATEC/MSEC scores for the age range from 2 to 7 years.
Keywords: ASD; autism; combinatorial language; language comprehension; language delay; prefrontal synthesis; receptive language; recursive language; syntactic language.