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)

Abstract

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. Electronic supplementary materialThe online version of this article (doi:10.1007/s00406-014-0571-z) contains supplementary material, which is available to authorized users.

Using Base Rate of Low Scores to Identify Progression from Amnestic Mild Cognitive Impairment to Alzheimer's Disease

“…This is, to our knowledge, the first study of the risk-AD when objective cognitive impairment is defined using the BRLS. Consistent with previous work, 12,13,30,31 we observed varying numbers of low scores in NCs, reflecting normal cognitive variability. Using the bottom 10% of the sample, we defined cognitive impairment as 3 or more low scores from among 9 tests administered.…”

Subtle Cognitive Decline and Biomarker Staging in Preclinical Alzheimer’s Disease

“…Another limitation of the current study is that ADNI participants undergo only a relatively brief battery of neuropsychological tests. A more extensive neuropsychological evaluation would enhance our ability to detect and more fully characterize subtle cognitive decline, provided that we are mindful of the possible increase in base rates of low scores with increasing numbers of tests [45, 46] and the resulting potential for misclassification [31]. By clearly defining “subtle cognitive decline” via sensitive and reliable neuropsychological test scores, and by re-exploring timelines of biomarker and cognitive changes, we hope to improve diagnostic precision of preclinical AD and sharpen our ability to identify early signs associated with different neurobiological pathways to the diagnosis of AD.…”

Neuropsychological Diagnostic Accuracy: Factors That Might Lead to a Wrong Diagnosis and How to Avoid Them

“…How common are low scores in healthy individuals? Mistridis et al (2015) determined base rates of low performance using the Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery (CERAD-NAB). In this study, 1081 adults participated between 49 and 92 years of age.…”

“…In total, 60.6% obtained scores at or below the 10th percentile. Mistridis et al (2015) provided information about the number of low scores that are required to determine probable cognitive impairment using different cut-off points. This diagnosis is established when the patient obtains a number of low scores that are observed in a percentage equal or less than 10% of the sample.…”