Mayo‐PACC: Optimizing a parsimonious Preclinical Alzheimer’s disease cognitive composite comprised of public‐domain measures

Abstract

AbstractBackgroundPreclinical Alzheimer’s cognitive composites (PACC) are designed to detect subtle cognitive changes in clinical trials. PACCs often include measures of memory, attention, and semantic fluency, with variations based on available measures. We created a Mayo Clinic PACC (Mayo‐PACC) to address limitations of existing PACCs by prioritizing parsimony, non‐proprietary measures, clinical applicability, and psychometric properties. We developed a Mayo‐PACC and examined sensitivity to detecting longitudinal cognitive change in amyloid positive (A+) older adults relative to the Preclinical Alzheimer’s Cognitive Composite‐Revised (PACC‐R). Exploratory analyses included comparison to other composites.MethodParticipants included 614 individuals in the Mayo Clinic Study of Aging (428 A‐ and 186 A+) age 65‐85 who were cognitively unimpaired at baseline with 7 years mean follow‐up. A+ was defined as PiB‐PET meta‐ROI SUVR ≥ 1.48 (centiloid 22). The Mayo‐PACC included the AVLT sum of trials (trials 1‐5, short delay, long delay), Trails B and Animal fluency. Measures included in the PACC‐R and other comparison composites are listed in Table 1. We calculated study‐specific z‐scores and examined psychometric properties of component measures including test‐retest reliability, practice effects, and distributional properties (ceiling/floor effects, skew, kurtosis). We examined sensitivity to preclinical cognitive change using slope estimates (difference in annualized change across A+ and A‐ groups) from linear mixed models (LMMs) for each composite. A jackknife procedure was used to calculate the standard error and subsequent confidence intervals of differences in rates of change (A+>A‐ indicating more significant decline in A+). Significance was determined based on whether the 95% Confidence Interval (CI) contained 0 (alpha = .05).ResultAll composites showed sensitivity to amyloid‐related longitudinal cognitive decline (A+>A‐ annualized change p<.05; see Table 2). Jack‐knife comparisons revealed comparable utility of Mayo‐PACC and PACC‐R (CI contained 0, see Table 3). Exploratory analyses revealed Mayo‐PACC performed similarly to an adaptation of the ADCS‐PACC, Global‐z, Memory‐z and Attention‐z. The Mayo‐PACC performed better than a 2‐measure Mayo‐PACC‐remote and a single memory measure.ConclusionThe Mayo‐PACC provides a parsimonious composite score that has comparable utility for detecting A+>A‐ cognitive decline compared to the PACC‐R and other composites and can be widely used in both research and clinical settings.