17771
Diagnostic Stability from Age 3-8 Years in a Canadian High-Risk Sibling Cohort
Objectives: To examine diagnostic stability, from 3 to 8 years of age, using longitudinal data from a high-risk cohort of younger siblings of children with ASD.
Methods: Participants were 51 high-risk infants (HR; younger siblings of children with ASD) followed from age 6-12 months to at least 8 years, drawn from our larger study. Blinded, clinical best estimate (CBE) diagnoses were made at 3 and 8 years, informed by the ADI-R, ADOS and DSM-IV-TR. Chi-Squared and Cohen’s Kappa were used to assess diagnostic stability across the two time points; file review provided additional details about children whose diagnoses were not stable across time points.
Results: Overall agreement between 3- and 8-year CBE diagnosis was good (Kappa = .64, p<.001). Of 51 high-risk infants followed to age 8, 14 received an ASD diagnosis at age 3 (27.4%; 12 male). By age 8, 12/14 retained their ASD diagnosis (85.7%; 11 male), and an additional 6 received a new diagnosis of ASD (3 male, 3 female); 31/37 retained their non-ASD status (83.8%). Of the two cases who ostensibly “lost” their 3-year ASD diagnosis, one (male) was judged to be “non-ASD” at age 5, but retained “other” (sub-threshold) ASD-related concerns at 8; the other (female) was characterized as having Asperger syndrome at age 5, but by age 8 was described as non-ASD with language and learning challenges. Of the six “new” ASD cases, 3 received an ASD diagnosis at age 5 (2 females had language delays and 1 male had “other/behavioural” concerns at 3). The remaining 3 cases (2 males, 1 female) had demonstrated “other” concerns at age 3 or 5 (e.g., social anxiety, behavioral inflexibility). The “new” diagnoses at 8 covered the full DSM IV spectrum (2=Autism; 2=Asperger syndrome; 2=ASD/PDD-NOS).
Conclusions: To our knowledge, this is the first report of stability and change in diagnosis from 3 to 8 years in a prospective high-risk infant sibling cohort. Only 2 children diagnosed with ASD at age 3 did not retain that diagnosis at age 8, although developmental concerns continued to be evident for both. Of the 6 cases not identified as ASD at age 3, three received that diagnosis at age 5 and the remainder at age 8. In all of these cases, other social, language and/or behavioural concerns had been identified by 3 or 5. Discussion will explore further the cognitive, learning, and language profiles, as well as ASD symptomatology of cases whose diagnoses changed. These findings highlight the relative stability of early diagnosis, but also shed light on factors that may contribute to variability in the emergence and expression of ASD between age 3 and 8.