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

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.