Considering the base rates of low performance in cognitively healthy older adults improves the accuracy to identify neurocognitive impairment with the Consortium to Establish a Registry for Alzheimer’s Disease-Neuropsychological Assessment Battery (CERAD-NAB)

European Archives of Psychiatry and Clinical Neuroscience, Jan 2015

It is common for some healthy older adults to obtain low test scores when a battery of neuropsychological tests is administered, which increases the risk of the clinician misdiagnosing cognitive impairment. Thus, base rates of healthy individuals’ low scores are required to more accurately interpret neuropsychological results. At present, this information is not available for the German version of the Consortium to Establish a Registry for Alzheimer’s Disease-Neuropsychological Assessment Battery (CERAD-NAB), a frequently used battery in the USA and in German-speaking Europe. This study aimed to determine the base rates of low scores for the CERAD-NAB and to tabulate a summary figure of cut-off scores and numbers of low scores to aid in clinical decision making. The base rates of low scores on the ten German CERAD-NAB subscores were calculated from the German CERAD-NAB normative sample (N = 1,081) using six different cut-off scores (i.e., 1st, 2.5th, 7th, 10th, 16th, and 25th percentile). Results indicate that high percentages of one or more “abnormal” scores were obtained, irrespective of the cut-off criterion. For example, 60.6 % of the normative sample obtained one or more scores at or below the 10th percentile. These findings illustrate the importance of considering the prevalence of low scores in healthy individuals. The summary figure of CERAD-NAB base rates is an important supplement for test interpretation and can be used to improve the diagnostic accuracy of neurocognitive disorders.

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Considering the base rates of low performance in cognitively healthy older adults improves the accuracy to identify neurocognitive impairment with the Consortium to Establish a Registry for Alzheimer’s Disease-Neuropsychological Assessment Battery (CERAD-NAB)

Panagiota Mistridis 0 1 2 4 5 6 7 Simone C. Egli 0 1 2 4 5 6 7 Grant L. Iverson 0 1 2 4 5 6 7 Manfred Berres 0 1 2 4 5 6 7 Klaus Willmes 0 1 2 4 5 6 7 Kathleen A. WelshBohmer 0 1 2 4 5 6 7 Andreas U. Monsch 0 1 2 4 5 6 7 0 G. L. Iverson Department of Physical Medicine and Rehabilitation, Harvard Medical School , Boston, MA 02114 , USA 1 P. Mistridis S. C. Egli A. U. Monsch Department of Psychology, University of Basel , Missionsstrasse 60/62, 4055 Basel , Switzerland 2 P. Mistridis S. C. Egli A. U. Monsch ( 3 ) Memory Clinic, Felix Platter Hospital, University Center for Medicine of Aging Basel , Schanzenstrasse 55, 4031 Basel , Switzerland 4 K. A. Welsh-Bohmer Joseph and Kathleen Bryan Alzheimer's Disease Center, Duke University , 2200W Main Street, Suite A200, Durham, NC 27705 , USA 5 K. Willmes Section Neuropsychology, Department of Neurology, RWTH Aachen University , Pauwelsstrae 30, 52074 Aachen , Germany 6 M. Berres Department of Mathematics and Technology, University of Applied Sciences Koblenz , Joseph-Rovan-Allee 2, 53424 Remagen , Germany 7 G. L. Iverson Red Sox Foundation and Massachusetts General Hospital Home Base Program , Boston, MA 02114 , USA It is common for some healthy older adults to obtain low test scores when a battery of neuropsychological tests is administered, which increases the risk of the clinician misdiagnosing cognitive impairment. Thus, base rates of healthy individuals' low scores are required to more accurately interpret neuropsychological results. At present, this information is not available for the German version of the Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery (CERAD-NAB), a frequently used battery in the USA and in German-speaking Europe. This study aimed to determine the base rates of low scores for the CERAD-NAB and to tabulate a summary figure of cut-off scores and numbers of low scores to aid in clinical decision making. The base rates of low scores on the ten German CERAD-NAB subscores were calculated from the German CERAD-NAB normative sample (N = 1,081) using six different cut-off scores (i.e., 1st, 2.5th, 7th, 10th, 16th, and 25th percentile). Results indicate that high percentages of one or more abnormal scores were obtained, irrespective of the cut-off criterion. For example, 60.6 % of the normative sample obtained one or more scores at or below the 10th percentile. These findings illustrate the importance of considering the prevalence of low scores in healthy individuals. The summary figure of CERAD-NAB base rates is an important supplement for test interpretation and can be used to improve the diagnostic accuracy of neurocognitive disorders. - When administered a battery of neuropsychological tests, some healthy older adults obtain low scores (e.g., [16]). Low test scores, especially low memory scores, obtained by healthy older adults might be interpreted as an indication of cognitive deterioration and lead to a false-positive diagnosis of mild cognitive impairment (MCI). Thus, to evaluate test results accurately and safeguard against misinterpretation of abnormal test performance, knowledge about base rates of low scores in healthy older adults compared to true pathological performance is of critical importance. Cognitive deficits, particularly in episodic memory, represent a hallmark of Alzheimers disease (AD) dementia and are known to be detectable in prodromal stages, such as MCI [79]. However, given that healthy older adults may also show a gradual but clinically insignificant cognitive decline over time [10, 11], these cognitive changes may be very subtle, such that in clinical practice detecting true cognitive impairment remains challenging [8]. Thus, to obtain an accurate understanding of an individuals cognitive functioning for a reliable and valid diagnosis, it is very important to differentiate normal changes with cognitive aging from cognitive changes that go beyond normal aging. At present, however, no universally accepted and empirically validated psychometric criteria exist to define cognitive impairment [12, 13]. Cognitive deterioration is broadly defined in clinical practice, and different cut-off scores are used to define impairment. Thus, when assessing cognitive impairment, some methodological issues have to be considered. When administering only one neuropsychological test, the number of individuals being within the lower tail of the Gaussian distribution will depend on the chosen cutoff score (e.g., when using the 7th percentile as the critical cut-off score, by definition, 7 % of cognitively healthy individuals would be erroneously classified as impaired). However, clinicians usually do not rely on a single test score, but on the patients performance on multiple tests when assessing cognition. The prevalence of low scores will then be considerably higher when the number of tests administered increases, compared to single test interpretation [1, 12]. Additionally, tests (...truncated)


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Panagiota Mistridis, Simone C. Egli, Grant L. Iverson, Manfred Berres, Klaus Willmes, Kathleen A. Welsh-Bohmer, Andreas U. Monsch. Considering the base rates of low performance in cognitively healthy older adults improves the accuracy to identify neurocognitive impairment with the Consortium to Establish a Registry for Alzheimer’s Disease-Neuropsychological Assessment Battery (CERAD-NAB), European Archives of Psychiatry and Clinical Neuroscience, 2015, pp. 407-417, Volume 265, Issue 5, DOI: 10.1007/s00406-014-0571-z