Education-Stratified Base-Rate Information on Discrepancy Scores Within and Between the Wechsler Adult Intelligence Scale-Third Edition and the Wechsler Memory Scale-Third Edition.

Abstract

The Wechsler Adult Intelligence Scale--Third Edition (WAIS-III; D. Wechsler, 1997a) and the Wechsler Memory Scale--Third Edition (WMS-III; D. Wechsler, 1997b) are 2 of the most frequently used measures in psychology and neuropsychology. To facilitate the diagnostic use of these measures in the clinical decision-making process, this article provides information on education-stratified, directional prevalence rates (i.e., base rates) of discrepancy scores between the major index scores for the WAIS-III, the WMS-III, and between the WAIS-III and WMS-III. To illustrate how such base-rate data can be clinically used, this article reviews the relative risk (i.e., odds ratio) of empirically defined "rare" cognitive deficits in 2 of the clinical samples presented in the WAIS-III--WMS-III Technical Manual (The Psychological Corporation, 1997).

Cognitive Discrepancies in Children at the Ends of the Bell Curve: A Note of Caution for Clinical Interpretation

“…These findings have significant implications for diagnostic accuracy, as individuals with lower IQ levels have a higher risk for false-negative errors, and individuals at higher IQ levels have a higher risk for false-positive errors in identifying acquired memory decline. Similar findings have been reported for discrepancies between individual index scores of the WMS-III and WAIS-III when stratified by educational level (Dori & Chelune, 2004). Patton and colleagues (Patton et al, 2006) also identified a similar pattern of discrepancies between the Total Scale score and individual indices on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS; Randolph, 1998) with older adults.…”

“…Additional studies have established differential base-rates of discrepancies with varying levels of pre-morbid functioning (Dori & Chelune, 2004;Hawkins & Tulsky, 2001;Matarazzo & Herman, 1985;Patton et al, 2006). Few studies have examined base-rates of cognitive discrepancies in children.…”

“…The stronger the correlation, the closer the two scores are expected to covary and the smaller the expected discrepancy. Specifically, as Dori and Chelune (2004) demonstrated, large discrepancies were rare in the normative sample for highly correlated indices, such as the WMS-III Auditory Immediate Index and Auditory Delayed Index (r ¼ .88; The Psychological Corporation, 1997, Table 4.14). In contrast, larger cognitive discrepancies were found between weaker correlated indices, such as the WMS-III Visual Immediate Index and the WAIS-III Perceptual Organizational Index (r ¼ .32; The Psychological Corporation, 1997, Table 4.11).…”

“…However, several important studies have subsequently identified unexpectedly large betweentest or subtest discrepancies in large normative samples, emphasizing the need for caution in interpreting discrepancy scores in isolation (e.g., Dori & Chelune, 2004;Heaton, Miller, Taylor, & Grant, 2004;Matarazzo, Daniel, Prifitera, & Herman, 1988;Matarazzo & Prifitera, 1989). Studies examining discrepancies between the Verbal IQ (VIQ) and Performance IQ (PIQ) indices from various versions of the Wechsler Adult Intelligence Scale (WAIS) in normal populations have highlighted the importance of considering both the statistical significance and base-rates of discrepancies in formulating clinical interpretations (Matarazzo & Herman, 1984).…”

Neuropsychological Contributions to the Early Identification of Alzheimer’s Disease

“…Asymmetric cognitive profiles can capture relative intraindividual differences by comparing performance on dissimilar neuropsychological tests or domains such as verbal relative to visuospatial abilities. Infrequent or atypical performance discrepancies may signal a neurodegenerative process and are frequently used in both clinical and research settings to identify potential changes from premorbid levels of cognitive functioning (Dori and Chelune 2004;Lange and Chelune 2006;Wilde et al 2001). Thus, asymmetric cognitive profiles may have utility for detecting a prodromal phase of AD for a number of reasons.…”