Building Consensus Around Adult Autism Diagnostic Assessment: A Mixed-Methods Approach

Abstract

Background:

Diagnosing autism in adulthood presents several challenges, including scant validated measures, overlapping characteristics with other conditions, and limited information regarding client preferences and experiences. We sought to generate consensus best practice (CBP, i.e., high endorsement or agreement by ≥75%) between expert clinicians and autistic adults around existing clinical practice guidelines (CPGs) and co-develop statements for enhancing practice.

Methods:

Thirty-five autistic adults and 30 expert clinicians participated in a three-round Delphi survey. Participants rated abbreviated versions of National Institute for Health and Care Excellence CPGs for adult autism diagnosis on importance, feasibility, and acceptability. In Round 1, participants also answered open-ended questions regarding what is currently working well, missing, and in need of improvement in adult autism assessment. We conducted thematic analysis on these open-ended responses to generate co-developed statements. In subsequent rounds, participants reviewed prior round ratings and comments and then re-rated CPGs (on all three metrics) and co-developed statements to generate CBP. They also selected their top five co-developed statements in Round 3.

Results:

By Round 3, both groups reached CBP on the importance of over 50% of CPGs, covering topics such as having trained professionals and assessing core autism features, mental health, and early development. However, they reached CBP less often on feasibility and acceptability. Clinicians reached CBP more often than autistic adults. Participants also reached CBP on most (24/31) co-developed statements, highlighting priorities like clear communication, neurodiversity-affirming care, and better access to diagnostic assessments. Participants did not reach CBP for informant involvement within the autistic adult group or for multidisciplinary evaluations across groups.

Conclusions:

While participants supported the importance of many CPGs, further research should address feasibility and acceptability challenges. CBP and co-developed statements may enhance adult autism assessments for both clinicians and autistic adults; however, empirical evaluation in clinical settings will be key.

Community Brief

Why is this an important issue?

Diagnosis of autism in adulthood is increasing in demand but complicated for various reasons. These include a lack of diagnostic tools developed or validated for use with adults, behavioral overlap with other conditions, and limited information about the needs, preferences, and experiences of those seeking diagnoses. While clinical practice guidelines (CPGs) for adult autism diagnosis are emerging globally, they remain limited in the United States and Canada. Incorporating the perspectives of expert clinicians and autistic adults across North America could lead to more effective and acceptable diagnostic practices. More broadly, improving adult autism diagnosis can increase access to support, promote self-understanding and acceptance, and improve mental health.

What was the purpose of this study?

We sought to generate consensus best practice (CBP) between expert clinicians and autistic adults around existing CPGs and co-developed statements for enhancing adult autism diagnostic practices.

What did the researchers do?

We used the Delphi method, which gathers expert feedback over multiple rounds to build consensus or highlight differing perspectives. We surveyed 30 clinicians with expertise diagnosing autism in adults and 35 autistic adults diagnosed in adulthood. In a three-round survey, participants rated existing CPGs on their importance, feasibility, and acceptability. They also answered open-ended questions about what is working well, challenging, and missing from adult autism assessment. We summarized their responses into statements for further review, revision, and rating in subsequent rounds. In the final round, participants selected their top five co-developed statements.

What were the results and conclusions of the study?

Autistic adults and clinicians agreed on the importance of more than half of existing CPGs (see Supplementary Fig. S4); however, fewer guidelines reached consensus on their feasibility and acceptability. Co-developed statements had higher levels of agreement and offered actionable recommendations, like improving communication and using neurodiversity-affirming approaches, and identified shared challenges and solutions—such as increasing access to assessments and improving clinician training.

What is new or controversial about these findings?

Our study took a novel approach by incorporating the perspectives of both autistic adults and expert clinicians to build CBP and co-create statements around adult autism diagnosis. Differences in perspective were not necessarily contradictory but complementary, offering a more nuanced understanding of the challenges and potential improvements in adult autism diagnostic practices. This approach can promote meaningful and effective changes that benefit all parties involved.

What are potential weaknesses in the study?

One limitation was the lack of diversity among participants (e.g., race/ethnicity, support needs, limited number of men), which may impact generalizability of the findings. Additionally, focusing on recent diagnoses (within the past 5 years) may have skewed responses, particularly for the autistic adult group, toward experiences involving remote assessments during the COVID-19 pandemic.

How will these findings help autistic adults now or in the future?

Our study highlights immediate steps and longer-term goals that can help improve adult autism assessments. By identifying shared priorities and challenges, the findings can inform training, policy, and practice changes that make the diagnostic process more accessible, affirming, and effective for future generations of autistic adults.