Table 6.
Sample size estimates showing a treatment effect of 25% in a hypothetical 3-year trial in subjects with MCI according to disease-stage classification at baseline
| Outcome measures | MCI (N = 873) | Prodromal AD (N = 420) | Prodromal AD stage-1 (N = 216) | Prodromal AD stage-2 (N = 197) |
|---|---|---|---|---|
| CSF Aβ1–42 (pg/mL) | 6545 (2218–82,165) | 5257 (1705–88,214) | - | 1469 (619–6964) |
| 18F-AV-45-PET (SUVr) | 9312 (2850–2,51,663) | - | 3925 (1074–5,00,647) | - |
| CSF tau (pg/mL) | 3611 (1539–16,455) | 2760 (1148–13,667) | 1791 (634–17,633) | 3577 (1044–1,62,076) |
| FDG-PET (SUVr) | 888 (662–1254) | 447 (330–640) | 486 (322–817) | 396 (262–665) |
| Whole-brain volume (cm3) | 165 (147–187) | 108 (94–126) | 120 (97–152) | 102 (85–125) |
| Hippocampal volume (mm3) | 200 (178–227) | 142 (123–167) | 197 (155–259) | 102 (85–123) |
| Ventricular volume (cm3) | 274 (236–322) | 231 (189–289) | 260 (191–373) | 185 (144–245) |
| CDR sum of boxes | 636 (536–765) | 443 (359–559) | 603 (433–897) | 355 (273–481) |
| MMSE score | 992 (803–1256) | 625 (488–830) | 1263 (791–2328) | 371 (283–507) |
| ADAS-Cog | 1420 (1105–1893) | 703 (548–933) | 1346 (854–2431) | 418 (318–573) |
| ADCS-PACC | 745 (583–985) | 433 (326–604) | 488 (308–889) | 395 (279–601) |
| ADCS-PACC without digit symbol test | 1509 (1160–2043) | 688 (528–932) | 1576 (934–3203) | 342 (262–465) |
Abbreviations: Aβ1–42, amyloid β 1-42; AD, Alzheimer's disease; ADAS-Cog, Alzheimer's Disease Assessment Scale-Cognitive; ADCS-PACC, Alzheimer's Disease Cooperative Study Preclinical Alzheimer Cognitive Composite; CDR, Clinical Dementia Rating scale; CSF, cerebrospinal fluid; FDG, fludeoxyglucose; AV-45, florbetapir; MCI, mild cognitive impairment; MMSE, Mini–Mental State Examination; PET, positron emission tomography.
NOTE. Sample size was estimated for a hypothetical 3-year randomized-controlled trial with two arms, showing an expected treatment effect of 25% reduction of decline in outcome measures with a power of 80%, a two-sided alpha of 5%, and a 10% annual dropout rate. “-” represents not calculated as slope is not significantly different from 0 (see Table 4). Data are mean (95% confidence interval).