title: Stability and change in autism spectrum disorder diagnosis from age 3 to middle childhood in a high-risk sibling cohort.
abstract: Considerable evidence on autism spectrum disorder emergence comes from longitudinal high-risk samples (i.e. younger siblings of children with autism spectrum disorder). Diagnostic stability to age 3 is very good when diagnosed as early as 18-24 months, but sensitivity is weaker, and relatively little is known beyond toddlerhood. We examined stability and change in blinded, clinical best-estimate diagnosis from age 3 to middle childhood (mean age = 9.5 years) in 67 high-risk siblings enrolled in infancy. Good agreement emerged for clinical best-estimate diagnoses (89.6% overall; kappa = 0.76, p < 0.001, 95% confidence interval = 0.59-0.93). At age 3, 18 cases (26.9%) were classified with "autism spectrum disorder": 17 retained their autism spectrum disorder diagnosis (94.4%; 13 boys, 4 girls) and 1 no longer met autism spectrum disorder criteria at follow-up. Among "non-autism spectrum disorder" cases at age 3, 43/49 remained non-autism spectrum disorder at follow-up (87.8%; 22 boys, 21 girls) and 6/49 met lower autism symptomatology criteria ("Later-Diagnosed"; 3 boys, 3 girls). Later-diagnosed cases had significantly lower autism spectrum disorder symptomatology and higher receptive language at age 3 and trends toward lower autism symptoms and higher cognitive abilities at follow-up. Emerging developmental concerns were noted in all later-diagnosed cases, by age 3 or 5. High-risk children need to be followed up into middle childhood, particularly when showing differences in autism-related domains.
authors.affiliation: University of Toronto, Canada Holland Bloorview Kids Rehabilitation Hospital, Canada jbrian@hollandbloorview.ca.
authors.forename: Jessica
authors.initials: J
authors.lastname: Brian
authors.affiliation: Dalhousie University, Canada IWK Health Centre, Canada.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Bryson
authors.affiliation: Dalhousie University, Canada IWK Health Centre, Canada.
authors.forename: Isabel M
authors.initials: IM
authors.lastname: Smith
authors.affiliation: University of Toronto, Canada Integrated Services for Autism and Neurodevelopmental Disorders, Canada.
authors.forename: Wendy
authors.initials: W
authors.lastname: Roberts
authors.affiliation: Kinark Child and Family Services, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Roncadin
authors.affiliation: University of Toronto, Canada Centre for Addiction and Mental Health, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Szatmari
authors.affiliation: University of Alberta, Canada Glenrose Rehabilitation Hospital, Canada.
authors.forename: Lonnie
authors.initials: L
authors.lastname: Zwaigenbaum
mesh_terms: D000067877:Autism Spectrum Disorder / Q000175:diagnosis* / Q000523:psychology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D035781:Siblings / Q000523:psychology*
keywords: autism spectrum disorder; diagnostic stability; middle childhood; sibling; toddler