Measuring autism with the ADOS-2 using a bifactor model.
ADOS-2 Module 3 scores rest on one broad autism trait plus social and repetitive sub-traits, so score them separately to guide treatment.
01Research in Context
What this study did
The team looked at ADOS-2 Module 3 scores from school-age kids with autism.
They ran several factor models to see how the test items group together.
A bifactor model won: one big autism trait plus two smaller factors for social affect and restricted-repetitive behaviors.
What they found
The bifactor fit the data best, so ADOS-2 scores can be split into three parts.
Cognitive scores did not link to any factor, so IQ did not sway the results.
Still, the RRB factor was weak, hinting the test may miss some repetitive signs.
How this fits with other research
Norris et al. (2012) tested the same modules but found no clear winner among models.
Albert et al. (2024) now shows a bifactor is best, so the picture sharpens with newer data.
Sipes et al. (2014) saw a three-factor toddler screener work best, but that was the BISCUIT, not the ADOS-2, so age and tool explain the gap.
Why it matters
You can now view Module 3 scores as general autism plus two narrow bands.
Track social affect and RRB separately to spot which domain needs the most help.
Watch for under-reported RRBs and probe with extra questions or direct observation.
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02At a glance
03Original abstract
The measurement of autism characteristics can be challenging due to variability of social impairments and restricted and repetitive behaviors or interests (RRBs). Psychometrically strong measures such as the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) can improve our capacity for thorough autism assessment. The conceptualization of the ADOS-2 has been shaped by research exploring the structure of its items, which evaluate autism traits associated with social affect and RRBs. Continuously refining our understanding of these items and their relations to other characteristics, such as cognition, is crucial for more accurate autism assessment and diagnosis. This study used data from a sample of 188 school-age children with mostly average cognitive functioning referred for clinical autism evaluations to (1) test the dimensionality of the ADOS-2, Module 3 (appropriate for children with relatively higher verbal ability), across two sets of items (i.e., algorithm only, algorithm with three non-algorithm RRB items) using confirmatory factor analysis (CFA) and (2) examine the relations of cognition to the dimensions tested in the ADOS-2. A bifactor model, featuring a general autism trait and two subfactors (RRB and Social Affect), provided superior fit for algorithm-only and algorithm with three non-algorithm items. Cognitive functioning was not significantly related to the general or specific factors in the model with only algorithm items. While the findings support the validity of the ADOS-2, it may not fully capture RRBs among children referred for autism. This study enhances our understanding of the ADOS-2, highlighting the utility of a bifactor model for characterizing its dimensionality, measuring autism traits with minimal cognitive influence, and identifying its limitations in assessing RRBs.
Autism research : official journal of the International Society for Autism Research, 2024 · doi:10.1002/aur.3245