The Autism Impact Measure (AIM): Meaningful Change Thresholds and Core Symptom Changes Over One Year from an Online Survey in the U.S.

Validated outcome measures with the capacity to reflect meaningful change are key to assessing potential interventions for autism spectrum disorder (ASD). We derive clinically meaningful change thresholds (MCTs) of the Autism Impact Measure (AIM) and identify factors associated with meaningful change. Baseline and 12-months follow-up survey of caregivers of 2,761 children with ASD aged 3-17 years from the U.S. Simons Foundation Powering Autism Research for Knowledge (SPARK) cohort were analyzed. Using caregiver-reported anchors for change, the 12-month change in estimated AIM MCT (95% confidence interval) for symptom improvement was -4.5 (-7.61, -1.37) points and 9.9 (5.12, 14.59) points for symptom deterioration. These anchor-based MCTs will facilitate future assessments of caregiver-reported change in AIM scores.