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Table 3 Sample size per arm for a hypothetical clinical trial using different cognitive outcome measures

From: Cognitive composites for genetic frontotemporal dementia: GENFI-Cog

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
  1. 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%)
  2. 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