Development of a Novel Self-Report Tool to Aid in the Assessment of Autism in Adulthood: The Autism Spectrum Trait Scale

Abstract

Background:

Autism spectrum disorder is a neurodevelopmental condition characterized by a spectrum of neuropsychological and behavioral differences. Due to historical changes in diagnostic criteria and a rapid increase in autism rates, there are likely many undiagnosed autistic adults. The current state of formal assessment for autism poses a severe ethical crisis as these assessments are often difficult to obtain, especially in adulthood. Self-report tools are sometimes used to alleviate the burden of identifying autism. However, commonly used self-report tools to aid in the identification of autistic-like traits in adults have significant limitations that threaten their reliability and validity. The purpose of this study was to develop and assess the psychometric properties of the Autism Spectrum Trait Scale (ASTS), a novel self-report tool that may aid in the identification of autistic-like traits in adults, developed using principal axis factoring procedures.

Methods:

Exploratory factor analysis (n = 764) was conducted to develop the factor structure, and confirmatory factor analysis (n = 761) was performed in a nonoverlapping sample to assess the factor model. Out of the 1525 participants, 507 were autistic and 1018 were not. Of the 507 autistic adults, 177 reported having a formal diagnosis, whereas 330 were self-diagnosed.

Results:

The results showed a stable four-factor model with good model fit (Tucker-Lewis Index [TLI] = 0.92, Comparative Fit Index [CFI] = 0.92, Goodness-of-Fit [GFI] = 0.88, root-mean-square error of approximation [RMSEA] = 0.05), strong internal consistency (α = 0.94), and criterion validity (r = 0.90, p < 0.001). The model demonstrated metric measurement invariance (Δ CFI = −0.008, Δ RMSEA = 0.001), acceptable sensitivity and specificity (area under the curve = 0.92), and the presence of a superordinate factor (TLI = 0.91, CFI = 0.92, GFI = 0.90, RMSEA = 0.05).

Conclusions:

These findings provide preliminary evidence for the use of the ASTS as a component of assessment for autism in adults.

Community Brief

Why is this an important issue?

Many undiagnosed autistic adults face difficulty in getting assessed and diagnosed because the process is often complicated and hard to access. However, getting a diagnosis is important because it reduces stigma and can help autistic individuals better understand themselves, connect with others, and access support and resources that can improve their overall well-being.

What was the purpose of this study?

This study tested the psychometric properties of the Autism Spectrum Trait Scale (ASTS), a new self-report tool developed by the researchers, to identify autistic-like traits in adults and facilitate proper assessment and diagnosis.

What did the researchers do?

The researchers attempted to follow best practices for developing and analyzing new scales. They first conducted an exploratory factor analysis with 764 participants to figure out how the scale should be structured. Then, they conducted a confirmatory factor analysis with a different group of 761 participants to check if the structure they found was accurate. A total of 507 participants had autism, with 177 formally diagnosed and 330 self-reporting their diagnosis. They conducted analyses comparing formal and self-reported diagnoses to better understand the group differences.

What were the results of the study?

The results showed that the new scale had four clear factors, was valid and reliable, and accurately identified autistic-like traits across different groups. In addition, an analysis of the final items revealed an overall factor based on the total score, demonstrating that the new scale effectively measured the construct of autism as a whole.

What do these findings add to what was already known?

There have been ongoing discussions about the need for a reliable and easy-to-use tool. However, there was no existing tool that covered such a wide range of autistic traits and met the highest standards for validity, reliability, and clinical accuracy—until the ASTS.

What are potential weaknesses in the study?

This study included both “self-reported” and “clinically diagnosed” autistic adults. Additional analyses compared the differences between these groups on the new scale and an already established scale for detecting autism in adults. While not all autistic participants were clinically diagnosed, this approach contributes to the literature by highlighting the number of undiagnosed adults who believe they meet diagnostic criteria for autism and offering additional insights into this population.

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

The new scale is available online for free, and people who take the ASTS can score it themselves using the ASTS scoring interpretation sheet to get results immediately. It can also be downloaded for printing. Undiagnosed autistic adults can use it to identify whether they may have autistic traits, and they can also bring the results to a formal assessment to discuss with a clinician. However, more research is needed before the ASTS can be officially used as part of the diagnostic process without the need for additional components.