Table 5.
Sample Size Estimatesa per Treatment Arm of a Clinical Trial Comparing 3 Different Outcome Measures to Detect a 20 to 50% Reduction in Rates of Change
| DTI Change, %/yr |
BBSI, ml/yr | Change in Graded Naming Test | ||||
|---|---|---|---|---|---|---|
| Right Cingulum Bundle |
Right Uncinate Fasciculus |
|||||
| % Change | FA | MD | RD | AX | ||
| 20 | 276 | 1,031 | 531 | 1,229 | 507 | 1,524 |
| 30 | 123 | 459 | 236 | 546 | 226 | 685 |
| 40 | 69 | 258 | 133 | 308 | 127 | 381 |
| 50 | 45 | 165 | 85 | 197 | 82 | 246 |
Sample size estimates have been adjusted for control rates of change.
a
β = 80%, α = 0.05.
AX = axial diffusivity; BBSI = brain boundary shift integral (a measure of whole brain atrophy); DTI = diffusion tensor imaging; FA = fractional anisotropy; MD = mean diffusivity; RD = radial diffusivity.