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. 2021 Jan 26;96(4):e619–e631. doi: 10.1212/WNL.0000000000011214

Figure 4. Sample Sizes Needed to Detect Aβ-PET Accumulation and PACC Score Decline.

Figure 4

(A and B) Sample size needed per arm to detect varying levels of change over 5 years with 80% power in (A) β-amyloid (Aβ)-PET accumulation and (B) Preclinical Alzheimer Cognitive Composite (PACC) score decline for groups with different ranges of Aβ burden measured in Centiloid (CL) at baseline. Power analyses were estimated from a combined Harvard Aging Brain Study (HABS), Alzheimer's Disease Neuroimaging Initiative (ADNI), and Australian Imaging, Biomarker and Lifestyle (AIBL) dataset measured in CL. As shown in the red line, an early intervention trial targeting individuals in the low 18 to 35 CL range would require the smallest sample to detect Aβ-PET accumulation because individuals in this range typically exhibit the highest rates of accumulation. However, detecting PACC decline in the low 18 to 35 CL range would necessitate very large sample sizes. Targeting individuals in the 18 to 50 CL range would minimize the sample size needed to detect PACC score decline while maximizing power to detect reduced Aβ-PET accumulation.