Table 3. MCI sample size estimates for structural measures and a clinical measure – without enrichment, and with respect to five enrichment strategies.

Measures	All	Aβ+	Aβ+Ptau+	MRI+	MRI+Aβ+	MRI+Aβ+Ptau+
Entorhinal	294 [204 456]	169 [116 279]	128 [89 207]	95 [70 141]	69 [48 114]	60 [42 100]
Amygdala	306 [221 460]	184 [128 300]	144 [101 233]	122 [90 181]	102 [71 174]	93 [64 159]
Hipp	392 [275 608]	230 [157 389]	210 [141 360]	152 [110 230]	125 [85 218]	132 [88 238]
Parahipp	403 [276 654]	238 [159 410]	195 [132 333]	149 [107 228]	118 [80 204]	117 [79 209]
Fusiform	448 [307 723]	252 [168 432]	203 [137 346]	202 [143 320]	159 [105 291]	136 [90 249]
Isthmus cing	497 [339 810]	324 [212 586]	302 [195 560]	298 [202 504]	235 [148 470]	230 [142 472]
Whole Brain	563 [345 1091]	403 [239 851]	364 [217 773]	307 [198 559]	257 [154 554]	248 [147 548]
CDR-SB	583 [416 894]	336 [228 579]	313 [209 554]	284 [201 453]	246 [161 468]	234 [151 455]

The 95% confidence intervals of the estimated sample sizes are shown in brackets. Sample size estimates are those required to detect 25% slowing in the rate of change in MCI (under various enrichment strategies) that is in excess of that seen in Aβ-negative (Aβ⁻) HCs (N = 58). P-values for selected pair-wise comparisons are in Tables 4 and 5.

Key: All = all MCI participants (no enrichment); Aβ⁺ = MCI participants who are Aβ-positive at baseline; Aβ⁺Ptau⁺ = MCI participants who are both Aβ- and Ptau-positive at baseline; MRI⁺ = MCI participants who have AD-like atrophy at baseline; MRI⁺Aβ⁺ = MCI participants who are Aβ-positive and have AD-like atrophy at baseline; MRI⁺Aβ⁺Ptau⁺ = MCI participants who are simultaneously positive for all three biomarkers; Hipp = Hippocampus; Parahipp = Parahippocampus; cing = cingulate; CDR = clinical dementia rating – sum of boxes score. See text for definition of positive biomarker status classification.