Protocol for a double-blind placebo-controlled randomised controlled trial assessing the impact of oral semaglutide in amyloid positivity (ISAP) in community dwelling UK adults

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Published online 2024 Jun 20. doi: 10.1136/bmjopen-2023-081401

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Table 2

Sample size estimations

Total number scanned for amyloid=316Number randomised=88Number of completers=75 (=88×0.86)	Power estimate^* assumingtau PET mean annual change (SD) of 0.05 (0.04)^† when untreated		Power estimate^* assumingtau PET mean annual change (SD) of 2.01 (2.97)^‡ when untreated
One-year change from baseline in mean tau accumulation with semaglutide	Alpha 0.05	Alpha 0.10	Alpha 0.05	Alpha 0.10
20% lower compared with placebo. Effect differences of 0.01 and 0.402, respectively	19.7%	29.9%	9.2%	16.0%
30% lower compared with placebo. Effect differences of 0.015 and 0.603, respectively	38.1%	50.8%	14.6%	23.4%
40% lower compared with placebo. Effect differences of 0.02 and 0.804, respectively	59.8%	71.6%	22.3%	33.0%

316 individuals need to be screened to randomise 88 participants, with 75 participants completing the study, assuming a 14% dropout rate.

^*Power calculation is based on a two-sample t-test assuming equal variance.

^†Hanseeuw, BJ et al.³² 2019 PMID: 31157827.

^‡Whittington A, Gunn R.³³ 2021 PMID: 33517326.