Sample size and impact of the coronavirus disease 2019 pandemic
coronavirus disease 2019
MAY, CORONAVIRUS DISEASE 2019
Before the initiation of the study, a sample size calculation was conducted using the primary outcome QoR-15, with a minimal clinical difference of 8.0, an alpha of 0.05 and a power of 0.80, resulting in a sample size of 36 patients, 18 in each group. An attrition rate of 25% was added and adjusted for the block size of eight leading to 48 patients needed for final inclusion.Due to the coronavirus disease 2019 (COVID-19) pandemic, the trial was temporarily closed down for inclusion three times (between 13 March 2020 and 1 September 2020, between 8 December 2020 and 1 May 2021 and between 20 December 2021 and 5 January 2022), on the recommendation of the steering committee consisting of R.D.B., S.O.D., C.J. and I.G. One of the centres (Department of Surgery, Slagelse Hospital) was not able to open for inclusion again after the second close-down. During the third close-down, the sample size and retention were re-evaluated by the principal investigator and steering committee. It was decided to conclude the trial after inclusion of 40 patients, because attrition was lower than expected and this would meet the goal of 36 patients concluding the trial as required in the original sample size calculation.