Table 3. Sample Size Estimates per Group in a 2-Arm Trial for 25% Reduction in Annual Change in Flortaucipir With 80% Power, Assuming No Attrition, in Persons Who Are Cognitively Unimpaired and 65 to 85 Years Old, Based on the Mayo Clinic Study on Aging.
| β-Amyloid group centiloid range | Mean (SD) annualized change | Sample size per treatment arm with bootstrapped 95% CIsb | |
|---|---|---|---|
| In SUVR from initial flortaucipir PET scana | As a percentage change from index scana | ||
| AD meta–ROI | |||
| 9-21 | 0.004 (0.014) | 0.31 (1.17) | 5227 (940->10 000) |
| 22-67 | 0.005 (0.020) | 0.39 (1.63) | 2481 (577->10 000) |
| ≥68 | 0.028 (0.028) | 1.95 (1.94) | 216 (101-619) |
| Entorhinal cortex | |||
| 9-21 | 0.007 (0.019) | 0.66 (1.78) | 6153 (841->10 000) |
| 22-67 | 0.007 (0.021) | 0.58 (1.83) | 4382 (672->10 000) |
| ≥68 | 0.032 (0.039) | 2.33 (2.66) | 319 (127-1517) |
| Inferior temporal | |||
| 9-21 | 0.004 (0.017) | 0.32 (1.30) | 5771 (1121->10 000) |
| 22-67 | 0.005 (0.022) | 0.37 (1.75 | 3006 (703->10 000) |
| ≥68 | 0.030 (0.033) | 2.00 (2.17) | 239 (113-624) |
| Lateral parietal | |||
| 9-21 | 0.003 (0.017) | 0.20 (1.39) | 2775 (640->10 000) |
| 22-67 | 0.004 (0.019) | 0.34 (1.67) | 1252 (375->10 000) |
| ≥68 | 0.017 (0.021) | 1.34 (1.67) | 282 (133-821) |
Abbreviations: AD, Alzheimer disease; PET, positron emission tomography; ROI, region of interest; SUVR, standardized uptake value ratio.
a
Unadjusted means and SDs. For tau PET signals, these are presented in SUVR units.
b
Sample size based on annualized change in SUVR and accounting for age, sex, and education.