Comparison of the Leiter International Performance Scale-Revised and the Stanford-Binet Intelligence Scales, 5th Edition in Children with Autism Spectrum Disorders

Both the Leiter International Performance Scale-Revised (Leiter-R) and the Stanford-Binet Intelligence Scales, 5th Edition (SB5) are standardized intelligence tests that can be used with a variety of special populations. The Leiter-R is a nonverbal assessment shown to be 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 (ASDs), data about the relationship between both measures are not available for the most recent editions of the tools. A retrospective chart review of patient files from a major children’s hospital was conducted, and data from 1,071 patients at risk of an intellectual or developmental disability were obtained. From that sample, analyses were conducted on 50 children with both the Leiter-R and the SB5. All participants received an ASD diagnosis and were between the ages of three and twelve years. The final sample contained 41 males (82%) and 9 females (18%), similar to the ratio found in the general population for ASDs. Age ranged from 36 to 131 months (M = 66.7, SD = 24.1). ASD diagnoses were AD (n = 26; 52%) and non-AD (n = 24; 48%). Mixed method ANOVAs and t-tests found that this population received significantly higher scores on the Leiter-R than the SB5 when evaluated based on the full sample. Analyses also showed a significant effect for diagnostic category, level of functioning, and age of the child. No differences were found between the two genders. These analyses strongly suggest that the Leiter-R and the SB5 may not be equivalent measures of intellectual functioning in children with ASDs. Because these children regularly scored between one and two standard deviations higher on the Leiter-R than SB5, it seems prudent to assume that a nonverbal measure like the Leiter-R may be an appropriate assessment for estimating the upper bounds for an ASD population. Alternatively, they may also suggest that the Leiter-R, by virtue of being a nonverbal intelligence test, assesses areas known to be strengths for those with ASDs. These findings are in line with previous work that utilized earlier editions of the measures.