Treatment effects in randomised trials using routinely collected data for outcome assessment versus traditional trials: meta-research study

To compare effect estimates of randomised clinical trials that use routinely collected data (RCD-RCT) for outcome ascertainment with traditional trials not using routinely collected data.; Meta-research study.; Studies included in the same meta-analysis in a Cochrane review.; Randomised clinical trials using any type of routinely collected data for outcome ascertainment, including from registries, electronic health records, and administrative databases, that were included in a meta-analysis of a Cochrane review on any clinical question and any health outcome together with traditional trials not using routinely collected data for outcome measurement.; Effect estimates from trials using or not using routinely collected data were summarised in random effects meta-analyses. Agreement of (summary) treatment effect estimates from trials using routinely collected data and those not using such data was expressed as the ratio of odds ratios. Subgroup analyses explored effects in trials based on different types of routinely collected data. Two investigators independently assessed the quality of each data source.; 84 RCD-RCTs and 463 traditional trials on 22 clinical questions were included. Trials using routinely collected data for outcome ascertainment showed 20% less favourable treatment effect estimates than traditional trials (ratio of odds ratios 0.80, 95% confidence interval 0.70 to 0.91, I; 2; =14%). Results were similar across various types of outcomes (mortality outcomes: 0.92, 0.74 to 1.15, I; 2; =12%; non-mortality outcomes: 0.71, 0.60 to 0.84, I; 2; =8%), data sources (electronic health records: 0.81, 0.59 to 1.11, I; 2; =28%; registries: 0.86, 0.75 to 0.99, I; 2; =20%; administrative data: 0.84, 0.72 to 0.99, I; 2; =0%), and data quality (high data quality: 0.82, 0.72 to 0.93, I; 2; =0%).; Randomised clinical trials using routinely collected data for outcome ascertainment show smaller treatment benefits than traditional trials not using routinely collected data. These differences could have implications for healthcare decision making and the application of real world evidence