Comparison of Verbal Episodic Memory Measures: Consortium to Establish a Registry for Alzheimer's Disease—Neuropsychological Assessment Battery (CERAD-NAB) versus California Verbal Learning Test (CVLT)

Archives of Clinical Neuropsychology 27 (2012) 510–519 Comparison of Verbal Episodic Memory Measures: Consortium to Establish a Registry for Alzheimer’s Disease—Neuropsychological Assessment Battery (CERAD-NAB) versus California Verbal Learning Test (CVLT) Irene R. Beck1†, Alexa Gagneux-Zurbriggen1†, Manfred Berres2, Kirsten I. Taylor1,3, Andreas U. Monsch1,* 1 Memory Clinic, Department of Geriatrics, University Hospital Basel, Basel, Switzerland Department of Mathematics and Technology, University of Applied Sciences Koblenz, Koblenz, Germany 3 Centre for Speech, Language and the Brain, Department of Experimental Psychology, University of Cambridge, Cambridge, UK 2 *Corresponding author at: Memory Clinic, Department of Geriatrics, University Hospital Basel, Schanzenstrasse 55, Basel 4031, Switzerland. Tel.: +41 61 265 31 93; fax: +41 61 265 37 94. E-mail address: (Andreas U. Monsch). Accepted 23 May 2012 Abstract Episodic memory is affected early in the course of dementia. Two well-established tests to assess verbal episodic memory functioning are the Word List task from the Consortium to Establish a Registry for Alzheimer’s disease Neuropsychological Assessment Battery (CERADNAB) and the California Verbal Learning Test (CVLT). In clinical and/or research settings, patients are typically administered either one or the other test, making statistical comparisons difficult. This study aimed to (i) compare the z-scores of these two tests in patients with MCI and different types of dementia and (ii) establish formulae to transform CERAD-NAB scores into CVLT scores and vice versa. Sixty-five patients completed both tests for the first time and within 10 days of each other. Pearson correlation coefficients indicated that the two tests assess similar aspects of episodic memory and that the CVLT is more sensitive to subtle episodic memory impairments. Finally, conversion formulae are provided and their implementation illustrated. Keywords: Alzheimer’s disease; Dementia; Elderly/geriatrics/aging; Learning and memory; Mild cognitive impairment; Statistical methods Introduction Episodic memory impairments are among the most common early cognitive signs of dementia (Bäckman, Small, & Fratiglioni, 2001; Cullum, Filley, & Kozora, 1995; Fox, Olin, Erblich, Ippen, & Schneider, 1998; Greenaway et al., 2006; Twamley, Legendre Ropacki, & Bondi, 2006; Welsh, Butters, Hughes, Mohs, & Heyman, 1991). Two well-established tests to assess episodic memory functioning in patients with mild cognitive impairment (MCI) or early dementia are the Consortium to Establish a Registry for Alzheimer’s disease—Neuropsychological Assessment Battery (CERAD-NAB) Word List task (Morris, Mohs, Rogers, Fillenbaum, & Heyman, 1988) and the California Verbal Learning Test (CVLT; Delis, Kramer, Kaplan, & Ober, 1987). Although both tests assess similar aspects of verbal episodic memory, most notably encoding, recall and recognition, important differences exist regarding test construction and demands. In particular, the CVLT was constructed to assess a broader range of verbal episodic memory-related functions, and is considered more demanding than the CERAD-NAB Word List task. Consequently, patients with progressive neurodegenerative diseases are often † These authors contributed equally to this work. # The Author 2012. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: . doi:10.1093/arclin/acs056 Advance Access publication on 19 June 2012 I.R. Beck et al. / Archives of Clinical Neuropsychology 27 (2012) 510–519 511 administered the CVLT in the early stages of their disease and the CERAD-NAB in more advanced stages, such that the statistical longitudinal evaluation of episodic memory functioning become difficult. These task differences are also relevant in research settings when investigators wish to compare the performances of patients examined with either one of these memory tests. Thus, the aims of this study were to examine whether the two verbal learning tests assess similar aspects of episodic memory and whether transformation formulae could be developed to transform the tests’ key variables into one another. Patients with amnestic MCI as well as those with different forms of dementia frequently complain about their episodic memory deficits, such as forgetting names or losing things (Jonker, Launer, Hooijer, & Lindeboom, 1996). Indeed, neuropsychological studies have demonstrated that episodic learning and recall best discriminate between healthy controls and preclinical Alzheimer’s disease (AD) patients and between preclinical AD and probable AD patients (Collie & Maruff, 2000; Twamley et al., 2006). Depending on the type of dementia, patients show limited learning, rapid forgetting, and/or impaired recognition of task information (Bäckman et al., 2001; Cullum et al., 1995; Fox et al., 1998; Greenaway et al., 2006; Grober, Lipton, Hall, & Crystal, 2000; Romàn, Erkinjuntti, Wallin, Pantoni, & Chui, 2002; Welsh et al., 1991). Consistent with these findings, magnetic resonance imaging studies typically report a significant reduction in hippocampal and entorhinal cortex volumes in patients with MCI and AD (De Leon et al., 1997; Du et al., 2001; Fox et al., 1996; Krasuski et al., 1998), two structures essential for episodic memory (Rempel-Clower, Zola, Squire, & Amaral, 1996; Squire & Zola-Morgan, 1991; Victor & Agamanolis, 1990). Given the importance of episodic memory deficits in the diagnosis of dementia, the assessment of verbal episodic memory is a crucial part of the neuropsychological examination of patients with suspected MCI or early dementia. The standardized neuropsychological assessment of dementia includes tests which measure the ability to learn new information, e.g., a list of words over a number of trials. The sum of immediately recalled (“immediate recall”) words constitutes “encoding”, i.e., the storage of incoming information into a mental representation (Butters, Delis, & Lucas, 1995). After a delay ranging between roughly 5 and 20 min, patients are requested to recall the encoded words, providing a measure of “delayed recall”. Finally, many standardized assessments of verbal episodic memory end with a recognition test. One well-established test of verbal episodic memory in dementia is the Word List task from the CERAD-NAB (Morris et al., 1988), a standardized serial learning task. Another widely used test is the CVLT (Delis et al., 1987), which assesses the same memory components as the CERAD-NAB Word List task, and additionally quantifies the different strategies people use to learn verbal information. Given the popularity of these two tests, it is important to know their relative usefulness and their possible interchangeability. As noted above, both tests assess similar aspects of verbal episodic learning and memory: encoding, delayed recall, and recognition. However, there are substantial differences in the task demands and format. For (...truncated)