Validation of the Updated (March 2025) Modified Checklist for Autism in Toddlers, Revised, with Follow-Up (M-CHAT-R/F) in Greek

Background/Objectives: The aim of this study was to translate, culturally adapt, and validate the updated (March 2025) version of the Modified Checklist for Autism in Toddlers, Revised, with Follow-Up (M-CHAT-R/F) in Greek by examining its reliability, validity, and screening efficacy in a Greek sample. Methods: The M-CHAT-R/F was administered to Greek parents/primary caregivers of children aged 16–48 months, with no prior diagnosis of autism spectrum disorder (ASD), severe sensory impairments, or other chronic conditions causing neurodevelopmental delay. Parents/primary caregivers were invited to participate in the nationwide Program “Child and Family Health Promotion through the Paediatric Framework” of the Greek Ministry of Health in collaboration with UNICEF, implemented by the National and Kapodistrian University of Athens. Results: The final sample comprised 280 parents of children 16 to 48 months old (mean age ± SD 24.64 ± 7.75 months) with an almost equal sex distribution. Mean (±SD) parental age was 35.31 (±3.14) years, ranging from 30 to 48 years, and most respondents were mothers (94.3%). The Greek M-CHAT-R/F demonstrated acceptable reliability (KR-20 = 0.789) and acceptable scalability (monotonicity). Conclusions: The present study provides compelling evidence that the Greek M-CHAT-R/F is a reliable, valid, culturally appropriate instrument for screening children for the presence of ASD. The psychometric properties of the Greek version are consistent with previous international reports and warrant its use in routine pediatric practice in Greece.