Lonnie Zwaigenbaum1, Jessica Brian2, Isabel M Smith3, Lori-Ann R Sacrey1, Martina Franchini4, Susan E Bryson3, Tracy Vaillancourt5, Vickie Armstrong6, Eric Duku7, Peter Szatmari8, Wendy Roberts9, Caroline Roncadin10. 1. Department of Pediatrics, University of Alberta, Edmonton, AB, Canada. 2. Department of Paediatrics, Bloorview Research Institute, University of Toronto, Toronto, ON, Canada. 3. Departments of Pediatrics and Psychology and Neuroscience, IWK Health Centre, Dalhousie University, Halifax, NS, Canada. 4. Department of Psychiatry, University of Geneva, Geneva, Switzerland. 5. Counselling Psychology, Faculty of Education, University of Ottawa, Ottawa, ON, Canada. 6. Autism Research Centre, IWK Health Centre, Halifax, NS, Canada. 7. Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada. 8. Department of Psychiatry, Centre for Addiction and Mental Health, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada. 9. Integrated Services for Autism and Neurodevelopmental Disorders, Toronto, ON, Canada. 10. McMaster Children's Hospital Autism Program, Hamilton Health Sciences, Hamilton, ON, Canada.
Abstract
BACKGROUND: Although early autism spectrum disorder (ASD) detection strategies tend to focus on differences at a point in time, behavioral symptom trajectories may also be informative. METHODS: Developmental trajectories of early signs of ASD were examined in younger siblings of children diagnosed with ASD (n = 499) and infants with no family history of ASD (n = 177). Participants were assessed using the Autism Observation Scale for Infants (AOSI) from 6 to 18 months. Diagnostic outcomes were determined at age 3 years blind to previous assessments. RESULTS: Semiparametric group-based modeling using AOSI scores identified three distinct trajectories: Group 1 ('Low', n = 435, 64.3%) was characterized by a low level and stable evolution of ASD signs, group 2 ('Intermediate', n = 180, 26.6%) had intermediate and stable levels, and group 3 ('Inclining', n = 61, 9.3%) had higher and progressively elevated levels of ASD signs. Among younger siblings, ASD rates at age 3 varied by trajectory of early signs and were highest in the Inclining group, membership in which was highly specific (94.5%) but poorly sensitive (28.5%) to ASD. Children with ASD assigned to the inclining trajectory had more severe symptoms at age 3, but developmental and adaptive functioning did not differ by trajectory membership. CONCLUSIONS: These prospective data emphasize variable early-onset patterns and the importance of a multipronged approach to early surveillance and screening for ASD.
BACKGROUND: Although early autism spectrum disorder (ASD) detection strategies tend to focus on differences at a point in time, behavioral symptom trajectories may also be informative. METHODS: Developmental trajectories of early signs of ASD were examined in younger siblings of children diagnosed with ASD (n = 499) and infants with no family history of ASD (n = 177). Participants were assessed using the Autism Observation Scale for Infants (AOSI) from 6 to 18 months. Diagnostic outcomes were determined at age 3 years blind to previous assessments. RESULTS: Semiparametric group-based modeling using AOSI scores identified three distinct trajectories: Group 1 ('Low', n = 435, 64.3%) was characterized by a low level and stable evolution of ASD signs, group 2 ('Intermediate', n = 180, 26.6%) had intermediate and stable levels, and group 3 ('Inclining', n = 61, 9.3%) had higher and progressively elevated levels of ASD signs. Among younger siblings, ASD rates at age 3 varied by trajectory of early signs and were highest in the Inclining group, membership in which was highly specific (94.5%) but poorly sensitive (28.5%) to ASD. Children with ASD assigned to the inclining trajectory had more severe symptoms at age 3, but developmental and adaptive functioning did not differ by trajectory membership. CONCLUSIONS: These prospective data emphasize variable early-onset patterns and the importance of a multipronged approach to early surveillance and screening for ASD.