Abstract
OBJECTIVE: Given the high autism spectrum disorder (ASD) recurrence risk in younger siblings, it is important to identify early ASD markers within this high-risk population. Although there is increasing evidence that the Modified Checklist for Autism in Toddlers-Revised, with Follow-Up Interview can identify many low-risk children during the second year of life, there has yet to be a study of how the M-CHAT-R/F functions in a high-risk sibling population at very young ages. METHODS: As part of a larger population-based study, the authors screened 74 infant siblings with the Modified Checklist for Autism in Toddlers-Revised, with Follow-Up Interview at 18 months and assessed diagnoses between the ages of 18 and 43 months. RESULTS: The M-CHAT-R/F had the highest positive predictive value for identifying children at risk of any developmental concern (i.e., ASD, language delay). Overall, 33% of siblings who presented for follow-up evaluations received ASD diagnoses with an additional 22% showing other developmental concerns. CONCLUSION: Failing the M-CHAT-R/F at 18 months of age raises significant concern that a child will show some degree of developmental difference or delay over time. These findings highlight the need for close developmental monitoring of this high-risk sample.