Accuracy of Initial Diagnostic Impressions of Autism Spectrum Disorder in Toddlers and Behaviors That Inform These Impressions

Clinicians form initial impressions about a child’s diagnosis based on behavioral features (de
Marchena & Miller, 2017); confidence in their initial impression may differ based on child’s
diagnosis and characteristics such as age (McDonnell et al., 2019). Initial impressions may
facilitate screening: 92% of referral-seeking children initially believed to have ASD are
ultimately diagnosed with ASD (Wieckowski et al., 2021). However, research has not yet
identified specific behaviors used to guide diagnostic impressions of ASD/non-ASD in toddlers.
Participants were toddlers (N=55, mean age 22.9 months) from a multi-site study investigating
early detection and intervention for ASD. Clinicians completed an Initial Diagnostic Impression
Checklist within five minutes of meeting a child. They noted their impression as ASD or non-
ASD, confidence in their impression, and the “atypical” or “typical” behaviors that contributed
to their impression: social reciprocity, nonverbal communication, eye contact, motor
mannerisms, prosody and vocalizations, facial expressions, and focus of attention. They also
noted confidence in the child’s final diagnosis. The final diagnostic groups were not significantly
different on race, ethnicity, maternal education, chronological age, or sex. When a child’s final
diagnosis was ASD (n=35), clinicians formed an initial impression of ASD in 22 cases
(sensitivity = 0.63). When a child’s final diagnosis was non-ASD (n=20), clinicians made an
initial impression of non-ASD in all cases (specificity = 1.00). Clinicians used the same four
behaviors to form accurate impressions of ASD and non-ASD: social reciprocity, nonverbal communication, eye contact, and focus of attention. Accuracy of impressions did not differ for
younger vs older toddlers, or based on developmental level. The current results suggest that
initial impressions accurately identified the majority (approximately 2/3) of toddler aged children
with ASD, but that a substantial minority of ASD toddlers are missed by initial impression.
These children require a lengthier and more in-depth evaluation to allow observation of ASD
characteristics.