Normative data beyond the total scores: a process score analysis of the Rey’s 15 word test in healthy aging and Alzheimer’s Disease

Background: The Rey's 15 words test is currently the most frequently used task in Italy to detect memory deficits in AD. The current standardised version is however quite outdated and lacks some cognitive indexes which may highlight problems in recall or encoding processes. The aim of the study was to update the normative data of the test and to consider some variables which were not accounted for in the original study, that is, recognition, learning rate and forgetfulness. We also adopted the process scores approach to ascertain the effects of serial position (primacy and recency). Methods: Three hundred ninety-six healthy participants were recruited. To detect any variables useful for intercepting the early stages of dementia, a group of 208 patients in the very early stage of AD was also recruited. Linear models were used to calculate the corrections scores for age, education, and gender, and ROCs were used to calculate cut-offs based on the maximum sum of sensitivity and specificity and the positive and negative predictive values. Results: All main indexes showed excellent Area Under the Curve (0.90-1), strong sensitivity and PPVs for distinguishing between the HCs and AD participants. However, the Intrusions index performed poorly in all parameters. Conclusion: The study provides updated, normative data which may be reliably used as a cognitive marker to detect early AD. The strength of the study is the large sample size and the number of indexes which make it possible to explore the utility of memory test process scores.