title: 18-month predictors of later outcomes in younger siblings of children with autism spectrum disorder: a baby siblings research consortium study.
abstract: OBJECTIVE
  Younger siblings of children with autism spectrum disorder (ASD) are at high risk (HR) for developing ASD as well as features of the broader autism phenotype. Although this complicates early diagnostic considerations in this cohort, it also provides an opportunity to examine patterns of behavior associated specifically with ASD compared to other developmental outcomes.
  
  
  METHODS
  We applied Classification and Regression Trees (CART) analysis to individual items of the Autism Diagnostic Observation Schedule (ADOS) in 719 HR siblings to identify behavioral features at 18 months that were predictive of diagnostic outcomes (ASD, atypical development, and typical development) at 36 months.
  
  
  RESULTS
  Three distinct combinations of features at 18 months were predictive of ASD outcome: poor eye contact combined with lack of communicative gestures and giving; poor eye contact combined with a lack of imaginative play; and lack of giving and presence of repetitive behaviors, but with intact eye contact. These 18-month behavioral profiles predicted ASD versus non-ASD status at 36 months with 82.7% accuracy in an initial test sample and 77.3% accuracy in a validation sample. Clinical features at age 3 years among children with ASD varied as a function of their 18-month symptom profiles. Children with ASD who were misclassified at 18 months were higher functioning, and their autism symptoms increased between 18 and 36 months.
  
  
  CONCLUSIONS
  These findings suggest the presence of different developmental pathways to ASD in HR siblings. Understanding such pathways will provide clearer targets for neural and genetic research and identification of developmentally specific treatments for ASD.
authors.affiliation: Yale University School of Medicine, New Haven, CT. Electronic address: Katarzyna.chawarska@yale.edu.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Chawarska
authors.affiliation: Yale University School of Medicine, New Haven, CT.
authors.forename: Frederick
authors.initials: F
authors.lastname: Shic
authors.affiliation: Yale University School of Medicine, New Haven, CT.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Macari
authors.affiliation: Amgen Inc., Thousand Oaks, CA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Campbell
authors.affiliation: University of Toronto.
authors.forename: Jessica
authors.initials: J
authors.lastname: Brian
authors.affiliation: Kennedy Krieger Institute and Johns Hopkins School of Medicine, Baltimore.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Landa
authors.affiliation: University of California, Los Angeles.
authors.forename: Ted
authors.initials: T
authors.lastname: Hutman
authors.affiliation: Harvard Medical School and Boston Children's Hospital.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Nelson
authors.affiliation: Medical Investigation of Neurodevelopmental Disorders (MIND) Institute at the University of California, Davis.
authors.forename: Sally
authors.initials: S
authors.lastname: Ozonoff
authors.affiliation: Boston University.
authors.forename: Helen
authors.initials: H
authors.lastname: Tager-Flusberg
authors.affiliation: Medical Investigation of Neurodevelopmental Disorders (MIND) Institute at the University of California, Davis.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Young
authors.affiliation: University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Lonnie
authors.initials: L
authors.lastname: Zwaigenbaum
authors.affiliation: New York State Institute for Basic Research in Developmental Disabilities, Albany, NY.
authors.forename: Ira L
authors.initials: IL
authors.lastname: Cohen
authors.affiliation: Institute of Psychiatry, King's College London.
authors.forename: Tony
authors.initials: T
authors.lastname: Charman
authors.affiliation: University of Miami.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Messinger
authors.affiliation: Marcus Autism Center, Children's Healthcare of Atlanta, and Emory University, Atlanta.
authors.forename: Ami
authors.initials: A
authors.lastname: Klin
authors.affiliation: University of California, Los Angeles.
authors.forename: Scott
authors.initials: S
authors.lastname: Johnson
authors.affiliation: Dalhousie University, Halifax, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Bryson
mesh_terms: D002659:Child Development Disorders, Pervasive / Q000175:diagnosis* / Q000235:genetics; D002675:Child, Preschool; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008297:Male; D012306:Risk; D035781:Siblings
keywords: ASD; broader autism phenotype; high-risk siblings; infants; predictors of outcomes