Chapter 6 - Serial Assessment with WAIS–IV and WMS–IV

Abstract

Clinicians frequently evaluate patients’ cognitive functioning over time. Patients may be re-evaluated to track cognitive decline associated with a degenerative disease, to aid in treatment planning, to identify medication effects on cognition, or to evaluate a change in cognitive status for diagnostic purposes. Comparing performance across time is complex and requires the clinician to consider multiple cognitive, statistical, and environmental factors. Using a simple heuristic (e.g., a change of one standard deviation between evaluations) can result in under- or over-estimation of a change in cognitive status. Applying appropriate statistical models helps the clinician control for practice effects, regression to the mean, and their interaction with characteristics of the individual (e.g., age and initial ability level). In this chapter, multiple regression techniques are applied to WAIS–IV and WMS–IV retest data to predict expected change in performance in healthy adults. The equations are derived for retesting with the same edition (i.e., WAIS–IV/WAIS–IV) and retesting with a different edition (i.e., WAIS–III/WAIS–IV, WISC–IV/WAIS–IV). The chapter describes the regression models and the use of comparison statistics for evaluating meaningful test score change (i.e., statistical significance and base rates). Challenges and limitations in identifying meaningful change in cognitive functioning are discussed.