Table 5.
Estimated sample sizes (95% CI) per arm (80% power at the 5% significance level to detect 25% reduction in disease progression) with and without controlling for normal aging using the STEPS-KN-BSI, pBSI1, pBSIγ, and gBSI taking into account the hippocampal atrophy rates
| STEPS-KN-BSI | pBSI1 | pBSIγ | gBSI | |
|---|---|---|---|---|
| 1.5 T | ||||
| Based on AD atrophy rates alone (N = 133) | 109 (81–150) | 147 (106–209) | 281 (186–458) | 106 (78–146) |
| Controlling for normal aging (N = 328) | 184 (127–271) | 253 (165–412) | 495 (285–1002) | 177 (121–271) |
| 3T | ||||
| Based on AD atrophy rates alone (N = 24) | 212 (83–700) | 217 (83–769) | 457 (153–3265) | 222 (82–840) |
| Controlling for normal aging (N = 63) | 265 (92–1320) | 276 (96–1310) | 590 (168–9900) | 250 (83–1329) |
| Comparison | Percentage difference of sample size (95% CI) |
|
|---|---|---|
| 1.5 T | 3T | |
| STEPS-KN-BSI versus gBSI | ||
| AD rates alone | −2.7 (−13.4 to 9.7), >0.05 | 4.8 (−20.9 to 31.8), >0.05 |
| Controlling for aging | −4.18 (−16.3 to 10.2), >0.05 | −5.8 (−31.7 to 26.2), >0.05 |
| pBSI1 versus gBSI | ||
| AD rates alone | −27.8 (−36.5 to −19.4), <0.05 | 2.4 (−23.9 to 34.5), >0.05 |
| Controlling for aging | −30.1 (−40.6 to −20.2), <0.05 | −9.4 (−36.4 to 25.8), >0.05 |
| pBSIγ versus gBSI | ||
| AD rates alone | −62.0 (−72.7 to −51.7), <0.05 | −51.3 (−76.3 to −20.3), <0.05 |
| Controlling for aging | −64.2 (−76.8 to −51.1), <0.05 | −57.7 (−86.5 to −22.6), <0.05 |
Key: AD, Alzheimer's disease; CI, confidence interval; gBSI, generalized boundary shift integral.