Developing a Measure of Adult Functional Outcomes in Autism Spectrum Disorder and Other Developmental Disabilities: Conceptual Model and Item Generation of the Adult Functioning Scale

Background and Purpose: Individuals with autism spectrum disorder (ASD) and other developmental disabilities (DD) continue to face considerable challenges in adulthood, experiencing difficulty in social functioning, independence, and maintaining competitive employment. However, researchers lack the ability to systematically assess adult outcomes in this population, relying on suboptimal reporting across gross categories (e.g., employed, not employed) or adaptive behavior scales developed for children. This absence of validated measures is a methodological barrier to supporting positive outcomes for these adults. This research includes first steps to develop efficient, validated, proxy and self-report measures of functional outcomes across a wide range of developmental disabilities – the Adult Functioning Scale (AFS).

Methods: Development of the AFS occurred in three phases. First, preliminary baseline data were collected from 62 autistic adults enrolled in an ongoing trial of Cognitive Enhancement Therapy. Participants completed the Vineland Adaptive Behavior Scales-3 (VABS-3), a scale widely validated for use with children and field standard measures of functional outcomes developed for adults with schizophrenia. General linear models were constructed to evaluate the sensitivity of these measures in assessing social functioning and employment in autistic adults. Next, a literature search was conducted to compare domains in existing functional outcome measures to inform AFS conceptual model development. Stakeholders reviewed the model, which was further revised, and items were generated. Finally, autistic adults (n = 15), adults with other DD (n = 7), caregivers of autistic adults (n= 13), and caregivers of adults with other DD (n = 10) completed in-depth cognitive interviews to assess comprehension of items and response categories, factors influencing how participants respond to items, and the inclusiveness of the item pool in capturing pertinent concerns.

Results: The VABS-3 demonstrated adequate sensitivity in detecting outcomes in social functioning; however, measures developed for adults with schizophrenia were more sensitive to differences in employment outcomes, suggesting that adult functional outcome measurement in this area can be improved. A final conceptual model was generated with 3 subdomains (social functioning, employment, and autonomy), including assessment of satisfaction within each domain for self-reporters. Cognitive interviews revealed that further revision of all subdomains is warranted, given heterogeneity across the population of adults with developmental disabilities.

Conclusions and Implications: This study developed the first conceptual model of functional outcomes specific to adults with developmental disabilities. Cognitive interviews revealed substantial heterogeneity necessitating greater attention to measuring nuanced contextual factors related to adult living, and potentially explaining why the VABS-3, which is widely validated for use with children, is insufficiently sensitive to variation in adult functional outcomes. Future work will involve the collection of data from 1000 self-reporters with ASD and other DD (e.g., Down syndrome, Fragile X, Williams syndrome, etc.), and their caregivers to conduct psychometric analyses and validate an efficient and broadly applicable measure of adult functional outcomes across a wide range of developmental disabilities. Improving measurement in this area is critical to better understanding the needs of adults with ASD and other DD, guiding their successful transition to and through adulthood, and enhancing services available to them.