Assessment of Intellectual Disability With the Wechsler Intelligence Scale for Children, Fifth Edition: Analysis of Part Score Profiles and Diagnostic Outcomes

Abstract

This study examined the group and individual part score profiles of individuals with mild intellectual disability (ID) who participated in a clinical validity study supporting the Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V) and a comparison group without ID derived from the WISC-V norming sample. Descriptive analyses revealed that both groups exhibited flat profiles of part scores (i.e., the five WISC-V factor indexes), with mean global composites and part scores in the Very Low range for the ID group and in the Average range for the comparison group. However, few participants in either group exhibited profiles similar to their respective group profile, and many in both groups exhibited substantial profile scatter. Examination of global composites and part scores obtained by individuals with ID revealed that the WISC-V’s global composites consistently identified those with ID using score thresholds of 70 to 75, but many individuals with ID obtained part scores much higher than this criterion. No meaningful differences were found between Black and White participants with ID. Implications focus on the risks associated with using part score elevation or profile scatter to defer identification of ID when all other criteria for the condition have been met. Impact Statement Because the cognitive profile of those with intellectual disability (ID) is generally low and flat, indicating a deficit in overall intellectual functioning with little variation among part scores, many presume that individuals with this disorder will exhibit the same pattern. Although most individuals with ID exhibit a low IQ consistent with the disorder, many exhibit much higher part scores, and significant part score scatter is common in individuals with ID. Failure to identify individuals with ID due to part score elevation or to significant profile scatter will likely have unintended negative consequences.