Validation of a clinical scale for restricted and repetitive behaviours in autism spectrum disorders

Background: Degrees of heterogeneity have been reported in the clinical expression of autistic syndrome, particularly in restricted and repetitive behaviours (RRB). These overwhelming behaviours represent a common problem over the whole autistic spectrum and comprise a wide range of behavioural manifestations that persist over time. Advances are needed in the understanding of this complex and heterogeneous clinical dimension of autism but to date there is no specific and thorough tool to provide accurate and standardized description of these behaviours.

Objectives: The validation of a clinical scale covering the full range of repetitive, restricted and stereotyped activities observed in autism spectrum disorders.

Methods: A checklist comprising 35 items dealing about RRB is used. Each item is scored on a five-point scale, from "never expressed" to "severely expressed and very characteristic of the person". Reliability and validity studies were performed on a sample consisting of more than 100 children, adolescents and young adults with autism or pervasive developmental disorders. These studies involved the participation of 15 centers.

Results: The scale has good inter-rater reliability and internal consistency. Content validity study, using principal component analysis, allowed the identification of 6 relevant main dimensions of RRB, i.e. "insistence on sameness", "sensory stereotypies", "motor stereotypies", "modulation of temper", "self-focused behaviours", and "vocal stereotypies".

Conclusions: The scale shows good psychometric properties and confirms the heterogeneity of RRB in autism spectrum disorders. The description of clusters of RRB helps identification of more homogeneous subgroups of patients, possibly related to different psychopathological or physiopathological underlying factors.