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

This study examined the recurrence rate of autism in siblings at elevated likelihood (EL) and the predictive validity of the Q-CHAT and ADOS-2 at 14 and 24 months (m) for a clinical best estimate (CBE) autism diagnosis at 3 years. 331 EL-siblings (47.9% girls) from the prospective longitudinal EuroSibs study underwent ADOS-2 assessments and caregivers completed the Q-CHAT at 14 m and 24 m. At 3 years CBE was determined using DSM-5 criteria. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were estimated. Autism recurrence rate was 25.7% [95% CI (21.1, 30.6)]. Q-CHAT sensitivity was 31.8% [95% CI (21.4, 43.6)] at 14 m and 30.6% [95% CI (20.7, 41.7)] at 24 m. Specificity was 81.2% [95% CI (75.4, 86.2)] at 14 m and 94.8% [95% CI (91.2, 97.2)] at 24 m. PPV was 35.6% [95% CI (24.2, 48.2)] at 14 m and 66.7% [95% CI (49.8, 81.1)] at 24 m. NPV was 78.5% [95% CI (72.6, 83.7)] and 79.9% [95% CI (74.7, 84.6)] respectively. ADOS-2 demonstrated a of 64.3% [95% CI (45.9, 80.2)] and 69.3% [95% CI (58.4, 79.0)] and a specificity of 71.1% [95% CI (60.3, 80.4)] and 68.7% [95% CI (62.5, 74.5)] at 14 m and 24 m respectively. PPV was 45% [95% CI (30.3, 60.4)] at 14 m and 41.9% [95% CI (33.5, 50.7)] at 24 m. NPV was 84.4% [95% CI (74.2, 91.8)] at 14 m and 87.3% [95% CI (81.9, 91.6)] at 24 m. Q-CHAT and ADOS-2 at 14 m and 24 m can aid in early differentiation between EL-siblings who need further assessment and those who do not, but neither has sufficient sensitivity and PPV for standalone CBE diagnosis prediction.