Investigating the Predictive Validity of the Quantitative Checklist for Autism in Toddlers and the Autism Diagnostic Observation Schedule-2 in Children at Elevated Likelihood for Autism.

The sample was highly educated and voluntary, so the results may not apply to families with different backgrounds or less access to services. Many children were excluded because no consensus diagnosis was available, and missing assessments were not imputed, especially at 14 months. Some 14-month ADOS-2 assessments may have been affected because not all children could walk or had developmental ages below 12 months. The outcome was a research consensus diagnosis at 36 months, which may not match routine clinical diagnoses. Follow-up ended at 36 months, so children with later-emerging autism or other conditions were not fully captured. Interventions received by children or parents were not accounted for and could have changed early behaviour.

Do not conclude that Q-CHAT or ADOS-2 can reliably identify which elevated-likelihood toddlers will later receive an autism diagnosis. Both tools missed many children who later received a diagnosis, and many children flagged as positive did not receive a diagnosis.