Optimizing Accuracy of Autism Diagnostic Observation Schedule-2 in Very Young Children With Modifying the Effect of Global Developmental Delay.
Lift the ADOS-2 CSS cut-off to 6 when global developmental delay is in the picture.
01Research in Context
What this study did
The team looked at ADOS-2 scores from very young children. Some kids had autism. Some had global developmental delay. Some had both.
They asked: does the usual cut-off still work when a toddler is behind in all areas?
What they found
A score of 5 caught most autism cases in toddlers without GDD.
When GDD was present, raising the cut-off to 6 worked better. The tool stayed very accurate for both groups.
How this fits with other research
Hong et al. (2021) already showed the Toddler Module cuts work well in plain autism. This new paper adds the GDD twist.
Geurts et al. (2008) found ADOS beat ADI-R in delayed toddlers. The 2026 study goes further by giving exact CSS numbers to use.
Bennett et al. (2008) saw the revised algorithm over-flag Hispanic kids with mild social issues. The 2026 data look rosier, but the kids here were younger and had clear GDD, explaining the gap.
Why it matters
You can keep using ADOS-2 with confidence. Just move the cut-off up one point when the child’s verbal reasoning DQ is below 75. This small shift lowers false positives and keeps your diagnosis solid.
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02At a glance
03Original abstract
The current study investigated 1144 toddlers and preschoolers (ASD + GDD n = 592; ASD only n = 249; GDD only n = 89; no ASD or GDD n = 214) with the toddler module (38.6%), Module 1 (57.5%), and Module 2 (3.9%) as well as Mullen Scales of Early Learning. The calibrated severity score (CSS) was used to compare severity across modules. The study sample was stratified by GDD (Visual Reception Developmental Quotient < 75), and each stratum was investigated with descriptive statistics, ROC curves, and test statistics to identify the optimal cut-off CSS to differentiate ASD and non-ASD. ROC analysis indicated that the CSS scores showed excellent discrimination for ASD status for both the GDD (AUC = 0.86) and no GDD (AUC = 0.95) strata. In the no-GDD stratum, an ADOS-2 CSS of 5 was determined to be the optimal cut-off. In the GDD stratum, an ADOS-2 CSS of 6 was determined to be the optimal cutoff. While non-spectrum/little-to-no concern and autism/moderate-to-severe concern showed very high predictive accuracy for diagnostic outcomes, the autism spectrum/mild-to-moderate concern lacked clear diagnostic directionality, regardless of GDD status. This is the first study with a large sample of toddlers and preschoolers exploring optimal ADOS-2 CSS cut-off when stratified by GDD.
Autism research : official journal of the International Society for Autism Research, 2026 · doi:10.1002/aur.70233