Developmental Profiles of Children Missed By Early Autism Screening Compared to Early-Identified Peers

Background: The American Academy of Pediatrics recommends that all children be screened for ASD at 18 and 24 months of age. ASD-specific screening and diagnostic tools for toddlers such as the M-CHAT and the M-CHAT-R/F make it possible for clinicians to make stable diagnoses at younger ages. However, no screening instrument can identify all cases at 18-24 months. Children who screen negative at 18-24 months old but later screen positive at 30-48 months old with the M-CHAT and M-CHAT-R/F are “potential miss” cases and provide important information about the natural course of ASD as well as the types of children likely to be missed by ASD-specific screening instruments.  

Objectives: This study presents data from a two-year follow-up screening with the M-CHAT and the M-CHAT-R/F examining the developmental and sociodemographic profiles of “potential miss” cases.

Methods: Participants were screened at pediatric well-visits at 18-24 months of age. Approximately 2 years after initial screening, children were rescreened with the M-CHAT-R/F; Children who screened positive at 18-24 months and/or 48 months were invited to complete an evaluation. Some children who screened negative at 18-24 months but positive at 48 months received an ASD diagnosis (Missed) (N=27) at 48 months. A subset of children maintained an ASD diagnosis from their initial evaluation to their 48 month evaluation (ASD; N=164).

Results: At 48 months, groups did not differ by age, gender, or race/ethnicity. Groups differed significantly on cognitive ability, adaptive skills, and symptom severity, with the Missed group showing stronger cognitive and adaptive skills and lower symptom severity. There was no difference between groups in the number of DSM-IV criteria met, though Missed children were more likely to receive a PDD-NOS diagnosis compared to the ASD children. Additionally, the groups significantly differed by the age at which first words and phrase speech developed, with the Missed group more likely to develop first words and phrases on time. Sibling status also differed between groups, with children in the Missed group more likely to be the oldest child or first child with ASD. Parent-reported age of first concern or regression did not differ between groups.

Conclusions: These findings indicate that a subset of children with ASD are more likely to be missed by ASD parent-report screening at 18-24 months, may not present with full symptom profiles, or may present with less severe symptoms and milder developmental delays at 18-24 months. These results also emphasize the importance of ASD screening at multiple time points, as a single screening may miss cases, or initial diagnosis may change. Understanding profiles of children who are not diagnosed until late toddlerhood can inform best practices for screening in the community and aid in measure development for ASD-specific screening tools.