A literature review of consent declines and consent withdrawals in randomized controlled trials conducted during the COVID-19 pandemic.

Objectives: We evaluated the extent of consent declines and consent withdrawals during the COVID-19 pandemic as seen in published randomized controlled trials (RCTs) and compared it with non-COVID-19 RCTs published at the same time and two historical controls. Methods: PubMed/Medline only was searched using key-word "COVID-19" and "RCTs" separately, and filtered for COVID-19 RCTs and non-COVID-19 RCTs respectively, published during a nine-month period (1 Feb - 1 Nov 2020). Exclusions were study protocols, observational studies, interim analysis of RCT data and RCTs with missing data. Primary outcome measures were the proportion of consent declines and consent withdrawals as percentage of total participants screened and randomized respectively in COVID-19 RCTs. We compared consent declines and consent withdrawals of COVID-19 RCTs with non-COVID-19 RCTs and two earlier studies on the same topic that served as historical controls (non-pandemic setting). Results: The search yielded a total of 111 COVID-19 RCTs and 49 non-COVID-19 RCTs. Of these, 39 (35.13%) COVID-19 RCTs and 11 (22.45%) non-COVID-19 RCTs were finally analysed. A total of 770/17759 (4.3%) consent declines and 100/7607 (1.31%) consent withdrawals were seen in 39 COVID-19 RCTs. A significant difference was observed in consent declines between COVID-19 vs non-COVID-19 RCTs [4.3% vs 11.9%, p < 0.0001] and between COVID-19 RCTs vs two historical controls [(4.3% vs 8.6%, p < 0.0001) and (4.3% vs 21.1%, p < 0.0001), respectively]. Conclusion: RCTs conducted during the COVID-19 pandemic appear to have significantly lower consent declines relative to non-COVID-19 RCTs during pandemic and RCTs conducted in non-pandemic settings.