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Peter Szatmari IMFAR 2008

Examining the Structure of the Repetitive Behavior Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder. Peter Szatmari IMFAR 2008. RBS-R background.

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Peter Szatmari IMFAR 2008

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  1. Examining the Structure of the Repetitive Behavior Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder Peter Szatmari IMFAR 2008

  2. RBS-R background • The Repetitive Behavior Scale-Revised (RBS-R; Bodfish et al. 2000) is a questionnaire (usually completed by parent) designed to examine restricted/repetitive behaviors in ASD • The RBS-R has 43 items organized in 6 subscales: • Compulsive • Ritualistic • Sameness • Self-Injurious • Stereotyped • Restricted Behavior

  3. Recent factor analytic study • Lam and Aman (2007), using a sample of children and adults (mean CA=184 months): • only five factors with a merged Ritualistic/Sameness factor • explained 47.5 % of the variance • Goodness of fit - RMSEA .06 (reasonable) • Some factors highly correlated

  4. Why do we use factor analysis ? • The two main objectives of factor analysis are: • to reduce a large number of variables to a smaller number of factors for modeling purposes • to create a set of factors to be treated as uncorrelated variables as one approach to handling multicollinearity in procedures as multiple regression (i.e. as predictors)

  5. Other studies • Repetitive sensory motor behaviours are associated with IQ, age, adaptive functioning, and other autistic symptoms (Szatmari et al. 2006, Hus et al 2007) • Insistence on sameness behaviours are independent of IQ, and other autistic symptoms (Hus et al 2007), BUT • Szatmari et al (2006): Insistence on sameness behaviours associated with autistic symptoms related to communication

  6. Objectives • To examine the factor structure of the RBS-R in a sample of preschool children with ASD • To examine the correlates of derived RBS-R factors in a sample of preschool children with ASD • General idea: use fewer, independent, empirical, dimensional variables (i.e. factors), to model human behaviours/symptoms/traits

  7. Community Services Family Child Social Competence Behaviour Adjustment Adaptive Functioning Communication Family well-being Pathways in ASD Study (N=400) • Describe how children with ASD change and develop over time and to identify factors associated with optimal outcomes. • Ecological • Multi-level • Longitudinal

  8. Sample: 225 newly-diagnosed children

  9. Analyses • Principal axis factor analysis with a Quartimax rotation with Kaiser Normalization was used to examine the structure of the RBS-R. • All 43 items of the RBS-R were used in the analysis • Pearson correlations were calculated to examine relationships between derived factors and other ASD symptoms, as well as cognitive and adaptive function.

  10. Stop at 3 factors Variance explained 40.20 % Confirmatory analyses RMSEA .047 (generally <.05 good fit) Results

  11. Results • A 3-factor solution was selected, using scree plot, goodness-of-fit criteria, and interpretability • The 3 factors were labeled: • Compulsive Ritualistic Sameness Behaviour (CRSB) • Self Injurious Behaviour (SIB) • Stereotyped Restricted Sensory Motor Behaviour (SRSMB) • The 3 factors were independent of each other:

  12. Results – items with highest loadings Compulsive Ritualistic Sameness Behaviour (CRSB) 38. Insists on routine 29. Placement of objects 39. Insists on time 37. Difficult transitions 27. Play/leisure routine 34. Appearance/behavior of others 31. No interruption 26. Transportation routine

  13. Results – items with highest loadings Self Injurious Behaviour (SIB) 7. Hits w/body 11. Pulls hair/skin 10. Bites self 8. Hits against surface 9. Hits w/object 13. Inserts finger/object 12. Rubs/scratches 14. Picks skin

  14. Results – items with highest loadings Stereotyped Restricted Sensory Motor Behaviour (SRSMB) 42. Preoccupied with part of object 43. Preoccupation with movement 3. Finger movements 5. Object usage 40. Preoccupation with subject 4. Locomotion 6. Sensory 2. Head movements 41. Attached to object 1. Body movements

  15. ORIGINAL SUBSCALES EMPIRICAL FACTORS Compulsive Behavior Subscale Compulsive Ritualistic Sameness Behavior (CRSB) Ritualistic Behavior Subscale Sameness Behavior Subscale Self-Injurious Behavior Subscale Self-Injurious Behavior (SIB) Stereotyped Behavior Subscale Stereotyped Restricted Sensory Motor Behaviour (SRSMB) Restricted Behavior Subscale Proposed RBS-R structure model for preschool children with ASD

  16. Correlations between factors and other variables

  17. Results • CRSB scores are positively associated with age, ADI-R scores, and SRS scores. • CRSB scores are negatively associated with Vineland adaptive behaviour composite • SRSMB scores are positively associated with ADOS scores, ADI-R scores (weak), and SRS scores • SRSMB scores are negatively associated with Merrill Palmer scores, and Vineland adaptive behaviour composite • SIB appears to be independent of other variables • Males score higher on the SRB factor (p<.01)

  18. Conclusions • The structure of the RBS-R can also be captured using fewer, more inclusive factors in a population of preschool children, compared with a previous factor analysis in an older sample • Our model satisfies both main objectives of factor analysis: • reduces a large number of variables (43) to a smaller number of factors (3) for modeling purposes (still explaining 40 % variance) • creates a set of factors to be treated as uncorrelated variables as one approach to handling multicollinearity in procedures like multiple regression (i.e. as predictors)

  19. Conclusions • If we exclude the Self-Injurious subscale • CRSB and SRSMB are similar to the empirical ADI-R Insistence on Sameness (IS) and Repetitive Sensory and Motor Behaviours (RSMB) factors (Szatmari et al. 2006, Cuccaro et al. 2003, Shao et al. 2003) • So more evidence for the High vs. Low level repetitive behaviours (even in young children)

  20. Future directions • This ongoing longitudinal study may reveal useful information on increasing differentiation of repetitive behaviours, as well as potential factors associated with their development • Examination of the stability/plasticity of the repetitive behaviours structure across time may provide useful information for interventions • Based on empirical factor loadings, one could develop algorithms with ‘weighted’ items (not simply adding items) that are more developmentally relevant for describing repetitive behaviours in children with ASD. • It will be interesting to see if these distinct empirical factors predict different behaviouralPathways of children with ASD

  21. Team effort for this presentation • Stelios Georgiades • Eric Duku • Isabel Smith • Pat Mirenda • Susan Bryson • Eric Fombonne • Wendy Roberts • Tracy Vaillancourt • Joanne Volden • Charlotte Waddell • Lonnie Zwaigenbaum • Pathways in ASD Study Team*

  22. *Pathways in ASD Study Team

  23. Acknowledgements • Children and families participating • Our sponsors: • Canadian Institutes of Health Research (CIHR) • Autism Speaks • British Columbia Government • Alberta Heritage Foundation for Medical Research

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