Table 3.
Sample size per arm for a hypothetical clinical trial using different cognitive outcome measures
| Outcome measures | C9orf72 | GRN | MAPT | ||||||
|---|---|---|---|---|---|---|---|---|---|
| ES 10% | ES 20% | ES 40% | ES 10% | ES 20% | ES 40% | ES 10% | ES 20% | ES 40% | |
| Cognitive composite scores | |||||||||
| Average composite | 306 | 76 | 19 | 27 | 7 | 2 | 124 | 31 | 8 |
| Weighted composite | 214 | 53 | 13 | 53 | 13 | 3 | 90 | 23 | 6 |
| Language | |||||||||
| Camel and Cactus Test | 4946 | 1237 | 309 | 292 | 73 | 18 | 357 | 89 | 22 |
| Boston Naming Test | 1109 | 277 | 69 | 213 | 53 | 13 | 223 | 56 | 14 |
| Category fluency | 1584 | 396 | 99 | 781 | 195 | 49 | 400 | 100 | 25 |
| Attention and mental processing speed | |||||||||
| Digit span forward | 13,0210 | 32,553 | 8138 | 2677 | 669 | 167 | 17,773 | 4443 | 1111 |
| Trail Making Test – part A | 2272 | 568 | 142 | 45 | 11 | 3 | 69 | 17 | 4 |
| Digit symbol | 254 | 64 | 16 | 925 | 231 | 58 | 80 | 20 | 5 |
| D-KEFS CWIT – colour naming | 866 | 216 | 54 | 502 | 126 | 31 | 66 | 17 | 4 |
| D-KEFS CWIT – word naming | 19,224 | 4806 | 1202 | 3310 | 828 | 207 | 150 | 37 | 9 |
| Executive functioning | |||||||||
| Digit span backward | 1724 | 431 | 108 | 840 | 210 | 52 | 26,218 | 6555 | 1639 |
| Trail Making Test – part B | 1275 | 319 | 80 | 25 | 6 | 2 | 81 | 20 | 5 |
| D-KEFS CWIT – ink naming | 61 | 15 | 4 | 70 | 17 | 4 | 26 | 7 | 2 |
| Phonemic fluency | 558 | 139 | 35 | 2229 | 557 | 139 | 161 | 40 | 10 |
| Visuoconstruction | |||||||||
| Benson figure copy | 5911 | 1478 | 369 | 2119 | 530 | 132 | 6,282,036 | 1,570,509 | 392,627 |
| Memory | |||||||||
| Benson figure recall | 1044 | 261 | 65 | 657 | 164 | 41 | 7611 | 1903 | 476 |
| FCSRT free recall | 1302 | 326 | 81 | 294 | 74 | 18 | 521 | 130 | 33 |
| FCSRT total recall | 1020 | 255 | 64 | 477 | 119 | 30 | 524 | 131 | 33 |
| FCSRT delayed free recall | 606 | 152 | 38 | 767 | 192 | 48 | 261 | 65 | 16 |
| FCSRT delayed total recall | 358 | 89 | 22 | 193 | 48 | 12 | 681 | 170 | 43 |
| Social cognition | |||||||||
| Facial Emotion Recognition Test | 7570 | 1892 | 473 | 7805 | 1951 | 488 | 147 | 37 | 9 |
The sample size per arm was estimated as n = (1 − ρ^2)(2σ^2)/δ^2 f(α,β), where ρ is the correlation between baseline and follow-up measures of the outcome, σ is the standard deviation of the outcome in the CDR® plus NACC-FTLD 0.5 group, δ is the treatment effect (effect size multiplied by the difference in mean between CDR® plus NACC-FTLD 0.5 and 1 group), α is the significance level (0.05), and 1 − β is the power to detect a treatment effect (80%)
Abbreviations: C9orf72 chromosome 9 open reading frame 72, GRN progranulin, MAPT microtubule-associated protein tau, ES effect size as a proportion of the difference between the outcome in the CDR® plus NACC-FTLD 0.5 group and the outcome in the CDR® plus NACC-FTLD 1 group, D-KEFS CWIT Delis-Kaplan Executive Function System Colour-Word Interference Test, FCSRT Free and Cued Selective Reminding Test