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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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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
RBS-R background Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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


Recent factor analytic study
Recent factor analytic study Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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


Why do we use factor analysis
Why do we use factor analysis ? Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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)


Other studies
Other studies Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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


Objectives
Objectives Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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


Pathways in asd study n 400

Community Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

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


Sample 225 newly diagnosed children
Sample: 225 newly-diagnosed children Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder


Analyses
Analyses Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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.


Results

Stop at 3 factors Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

Variance explained 40.20 %

Confirmatory analyses RMSEA .047 (generally <.05 good fit)

Results


Results1
Results Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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:


Results items with highest loadings
Results – items with highest loadings Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

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


Results items with highest loadings1
Results – items with highest loadings Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

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


Results items with highest loadings2
Results – items with highest loadings Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

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


Proposed rbs r structure model for preschool children with asd

ORIGINAL SUBSCALES Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

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


Correlations between factors and other variables Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder


Results2
Results Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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)


Conclusions
Conclusions Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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)


Conclusions1
Conclusions Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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)


Future directions
Future directions Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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


Team effort for this presentation
Team effort for this presentation Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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*


Pathways in asd study team
* Scale-Revised (RBS-R) in Young Children with Autism Spectrum DisorderPathways in ASD Study Team


Acknowledgements
Acknowledgements Scale-Revised (RBS-R) in Young Children with Autism Spectrum Disorder

  • 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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