Abstract
Objective: Low scores on neuropsychological tests are considered objective evidence of mild cognitive impairment. In clinical practice and research, it can be challenging to identify a cognitive deficit or mild cognitive impairment in high-functioning people because they are much less likely to obtain low test scores. This study was designed to improve the methodology for identifying mild cognitive impairment in adults who have above average or superior intellectual abilities.Method: Participants completed the National Institutes of Health Toolbox for the Assessment of Neurological and Behavioral Function Cognition Battery (NIHTB-CB). The sample included 384 adults between the ages of 20 and 85 who had completed either a 4-year college degree or who scored in the above average, superior, or very superior range on a measure of intellectual functioning, the Crystallized Composite score. Algorithms were developed, based on the absence of high scores and the presence of low scores, for identifying mild cognitive impairment.Results: Base rate tables for the presence of low scores and the absence of high scores are provided. The base rate for people with high average crystalized ability obtaining any one of the following, 5 scores <63rd percentile, or 4+ scores <50th percentile, or 3+ scores ≤ 25th percentile, or 2+ scores ≤ 16th percentile, is 15.5%.Conclusions: Algorithms were developed for identifying cognitive weakness or impairment in high-functioning people. Research is needed to test them in clinical groups, and to assess their association with clinical risk factors for cognitive decline and biomarkers of acquired neurological or neurodegenerative diseases.
Highlights
Deficit measurement is the sine qua non of clinical neuropsychology
Published studies reported low and high score base rates using the entire NIHTB-CB normative sample, including those with preexisting neurodevelopmental, psychiatric, substance use, and neurological disorders (Holdnack et al, 2017; Karr and Iverson, 2020), whereas these base rates were re-calculated for the current study including only those participants who did not report any of these pre-existing conditions
Base rates are presented for several different cutoff scores, including ≤25th, ≤16th, ≤9th, ≤5th, and ≤2nd percentiles for both age-adjusted normative scores and demographic-adjusted normative scores
Summary
Deficit measurement is the sine qua non of clinical neuropsychology. Low scores on neuropsychological tests are used to define a cognitive deficit or mild cognitive impairment (Heaton et al, 1991, 2004; Reitan and Wolfson, 1993; Petersen et al, 1999; Dubois et al, 2007). Even within a single cognitive domain, such as memory or executive function, it is common for healthy children, adults, and older adults to obtain one or more low test scores (Brooks et al, 2008, 2009b,c; Karr et al, 2017, 2018; Cook et al, 2019) This makes it challenging to accurately identify mild cognitive impairment (Petersen et al, 1999; Albert et al, 2011) or mild neurocognitive disorder, based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria (American Psychiatric Association, 2013), because these diagnostic criteria require test performance that is greater than one SD from the mean, but the criteria do not specify exactly how that is determined—such as whether one or more test scores in this range are required
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