Use of the Leiter International Performance Scale-Revised with Children with Autism Spectrum Disorders

Background: Both the Leiter International Performance Scale-Revised (Leiter-R) and the Stanford-Binet 5th Edition (SB5) are standardized intelligence measures that can be used with a variety of specialty populations. The Leiter-R is a nonverbal assessment measure useful in evaluating clients with restricted language capabilities. Although the Leiter-R and more traditional SB5 are frequently used to assess intellectual ability in children with autism spectrum disorders (ASD), data about the relationship between these measures are not available for the most recent editions of the tools. Objectives: To determine whether children with ASD appear to function differently when assessed using the nonverbal Leiter-R than the verbally-presented SB5, and to evaluate whether the magnitude of this relationship changes with the age of the child. Methods: A retrospective chart review of patient files from a major children's hospital was conducted, and data from 1,063 patients at risk for an intellectual or developmental disability were obtained. From that sample, analyses were conducted on 129 children who received both the Leiter-R and the SB5 and also an ASD diagnosis (Autistic Disorder: n=68, Pervasive Developmental Disorder Not Otherwise Specified: n=57, and Asperger's Disorder: n=4). In all, 83.7% were male (n = 108); mean age of the sample, in months, was 67.09 (SD = 34.06). Results: Preliminary results indicate that children with ASD performed significantly higher on the nonverbal Leiter-R (mean = 89.59, SD = 23.00) than the SB5 (mean = 70.04, SD = 19.09). This difference was both statistically [t(128) = 15.92, p < .0001, effect size = 1.40] and clinically significant. Planned analyses that will be available by the conference will examine whether the ages of the children or their levels of intelligence alter the relationship between the two measures, and if the severity of discrepancy is greater given a specific diagnosis (Autistic Disorder, PDD-NOS, or Asperger's Disorder). Conclusions: Clinicians use intelligence measures not only to aid in the diagnostic process, but also to make clinical recommendations regarding education and treatment options. The average 19.55 point discrepancy between mean scores of the two tests is substantial, and it may have important implications for clinical recommendations and decisions. Furthermore, it is important to realize that the mean difference between the two instruments was approximately 20 points, meaning that it was substantially larger in some children. In many cases, it will be important to obtain information with both a nonverbal test like the Leiter-R as well as a more general estimate of IQ (like the SB5), as this would give a better representation of the intelligence of the child than a single test alone, as well as areas of strength and relative deficit. Children with ASD have a unique set of impairments, and understanding the breadth of their abilities and the impact that a communication deficit has on a particular child can be both clinically and practically relevant.