Research without prior consent procedure and intervention effect on mortality in critical care: a meta-epidemiological study of randomized controlled trials

In critical care randomized controlled trials (RCTs), obtaining informed consent from patients or proxies can be challenging and may delay randomization, potentially affecting intervention efficacy. Research without prior consent (RWPC) procedures are increasingly used to facilitate timely inclusion but their impact on trial outcomes remains uncertain. We aimed to assess whether RWPC procedures are associated with differences in intervention effects on mortality in critical care RCTs. We searched PubMed and the Cochrane Database of Systematic Reviews from inception to August 1, 2024. We included meta-analyses of RCTs evaluating therapeutic interventions in critically ill adults, reporting mortality as a primary or secondary outcome. We conducted a meta-epidemiological study using a two-step approach. First, we calculated the ratio of odds ratios (ROR) within each meta-analysis to compare the effect of interventions on mortality between RCTs using RWPC and those using standard consent. Second, we pooled these RORs across meta-analyses using a random-effects model. Secondary outcomes included the delay from eligibility to randomization and the recruitment rate. We included 42 meta-analyses comprising 323 RCTs and 103,011 patients, of which 59 RCTs (18%) used a RWPC procedure. Trials using RWPC were more recent (median year: 2015 [2008–2019] vs. 2012 [2007–2017]; p < 0.01), larger (sample size: 203 [101–605] vs. 72 [40–162]; p < 0.01), more frequently multicenter (80% vs. 43%; p < 0.01), and had lower overall risk of bias. There was no significant difference in intervention effect on mortality between trials with and without RWPC (pooled ROR, 1.05 [95% CI 0.83–1.34]; I²=71.7%). RWPC was associated with shorter time to randomization (3 [1−9] vs. 11 [4−23] hours; p < 0.01) and higher recruitment rates (9.6 [4.7–18.7] vs. 4.5 [1.9–8.6] patients/month; p = 0.01). In critical care RCTs, RWPC procedures were not associated with differences in intervention effect on mortality but were linked to shorter time to randomization and higher recruitment rates.