How Much Change In Imitation Aptitude Is True Change?

Background:
The teaching of imitation skills is often the first step in interventions for young learners with intellectual disabilities and autism spectrum disorders. Although the existing literature on effects of imitation teaching provides evidence that this kind of early intervention strategy improves the prognosis of the children, research findings are based on methodologically weak studies, including the absence of a systematic imitation assessment.

Preschool Imitation and Praxis Scale (PIPS): 
The Preschool Imitation and Praxis Scale (PIPS) is a reliable and valid measure to identify preschoolers with imitation problems (Vanvuchelen, Roeyers, & De Weerdt, 2010; Vanvuchelen, Roeyers, & De Weerdt, 2011). However knowing that the PIPS has achieved a certain level of psychometric adequacy to identify preschoolers with imitation problems says nothing about its sensitivity to treatment-related changes in child functioning. To be clinically meaningful the PIPS must be reliable enough to evaluate outcomes of a therapeutic intervention, such as teaching imitation skills. To determine if the imitation aptitude has changed, an examiner must know what part of the difference between children’s measurements is attributable to real change, and what part is due to measurement error.

Objectives:  
The aim of this study was to determine the smallest detectable difference at 95% confidence of the PIPS in preschoolers with intellectual disabilities of heterogeneous aetiology, including children with low-functioning autism.

Methods:
Two raters independently scored videotapes of the imitation performance on the PIPS of 44 preschoolers (7 with Low-functioning Autism, 10 with Non-Specific Mental Retardation and 27 with Down syndrome) between 13 and 58 months of age (mean age 39.6 months, SD 11.9 months). The children with Low-functioning Autism were diagnosed according to a multidisciplinary clinical consensus classification in addition to a positive ADOS-G-classification.

Results:  
Results revealed that the PIPS demonstrated acceptable interrater reliability on item level (weighted kappa values ranged from .52 to 0.96) and scale level (ICC= 0.986; 95% CI: 0.975-0.993). The smallest detectable difference of the PIPS was 7.2%, indicating that the change score rated by different raters for an individual child with an intellectual disability is valid.

Conclusions:  
The Preschool Imitation and Praxis Scale (PIPS) can be used by early interventionists and researchers as an outcome measure to determine children’s maturation or improvement. For further research we suggest the investigation of the utility of the PIPS in a randomised controlled trial to evaluate the effectiveness of different intervention programs for improving the imitation skills of young learners with imitation problems.

References:  
Vanvuchelen, M., Roeyers, H., De Weerdt, W. (2011). Development and initial validation of the Preschool Imitation and Praxis Scale (PIPS). Research in Autism Spectrum Disorders, 5(1), 463-473.
Vanvuchelen, M., Roeyers, H., De Weerdt, W. (2010). Imitation assessment and its utility to the diagnosis of autism: Evidence from consecutively clinical preschool referrals for suspected autism. Journal of Autism and Developmental Disorders, in press.