P4‐293: COMPARISON OF THREE NORMATIVE DATA CORRECTION APPROACHES: A CROSS‐SECTIONAL EVALUATION IN THE AIBL STUDY

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During the development and validation of neuropsychological measures for native English speakers, normative data are typically collected from healthy normal individuals across an age range (e.g. 18-90 years-old) and from a specified geographic region (usually the USA). However, these norms may not be valid across geographically/culturally different populations. The purpose of this investigation was to compare, within a large Australian cohort, published norms against those derived from a, within-study, large sub-cohort of healthy individuals, as well as to examine the impact of a variety of demographic, clinical and biomarker variables on normative standards. Data from the Australian Imaging, Biomarkers and Lifestyle Study were used to compare three different normalisation procedures: (i) published population norms; (ii) norms derived from within-study participants who remained healthy over 3-years; (iii) norms derived from within-study amyloid negative (PiB-PETSUVR<1.5) participants who remained healthy over 3 years. The published norms were age, education and/or gender corrected. Multiple linear regressions were used to derive norms from within-study, with covariates including age, education, gender, premorbid IQ, and depressive symptomatology. Deviations from the raw data were assessed. Efficacy of the norms was examined cross-sectionally with receiver operating characteristics for separating a well defined HC population (3-years stable, amyloid negative) from diseased populations (AD, MCI or amyloid positive HC). There was generally good alignment between the normed and raw data. Differences in the normed data were exacerbated in more diseased groups (AD>MCI>HC). There was a general, expected, increase in efficacy for stratifying more severely diseased participants (AD>MCI>amyloid positive HC). A systematic trend shows that population norms are not as effective as the within-study derived norms for differentiating between a well defined HC population and diseased populations. However, overlap is seen between the 95% CI's and CVLT-II Immediate Recall represents an exception. Further, the population norms were comparable to the within-study derived norms for differentiating the AD population. Stable HC amyloid negative derived norms were not as consistent as the stable HC derived norms at stratifying diseased populations. This study considers the important assessment of the choice of population and norming variables (age, gender, etc.) when selecting for cognitive measures.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.