Overall bias and sample sizes were unchanged in ICU trials over time: a meta-epidemiological study

Objective: To assess time trends in risk of bias (RoB) and sample sizes in randomized clinical trials (RCTs) of adult intensive care unit (ICU) patients.

Study design and setting: A meta-epidemiological study of RCTs from Cochrane systematic reviews assessing interventions in adult ICU patients. Using run charts, we assessed time trends in the annual proportion of RCTs with overall low RoB, the annual median sample sizes, and the annual proportion of RCTs with low, unclear, and high RoB in individual bias domains.

Results: We included 604 RCTs published between 1977 and 2018 from 53 Cochrane systematic reviews. Only 6.8% of the RCTs had overall low RoB. We observed only random variation in the annual proportions of RCTs with overall low RoB, in the annual median sample sizes and in most individual bias domains. For "allocation concealment," we observed an increase in the proportion of low RoB RCTs and a decrease in the unclear RoB RCTs.

Conclusions: Few RCTs in adult ICU patients had overall low RoB. We found no evidence of an increase in RCTs with overall low RoB or in the median sample sizes over time. The only individual RoB domain with better ratings over time was "allocation concealment."