No difference were found between effect estimates from conventional and registry-based randomized controlled trials.

OBJECTIVE: The study aims to assess whether the results from registry-based randomized trials (RRCTs) systematically differ from the results of conventional randomized controlled trials (CRCTs).

STUDY DESIGN: Meta-epidemiological study. We identified RRCTs (02/2016) and subsequent systematic reviews (SRs) that included one RRCT (04/2017). We calculated pooled odds ratios for RRCTs and CRCTs for mortality and other incidence measures (e.g., cardiovascular events). We assessed the agreement between RRCTs and CRCTs using various measures with descriptive statistics and the odds ratio of pooled odds ratios (OROR) for RRCT(s) versus CRCTs. An OROR of >1 indicates that the effect estimates from RRCTs were larger than the effects estimates from CRCTs.

RESULTS: Overall, we compared 15 and 14 effect estimates for mortality and incidence measures, respectively. The 95% confidence interval (CI) overlap was 100% for any outcome. Conflicting effect directions were observed in 27% (4/15) of mortality and 7% (1/14) of incidence measures. The pooled odds ratio of odds ratios for RRCT(s) versus CRCTs was 1.03 (95% CI 0.97 to 1.09) for mortality and 1.05 (95% CI 0.98 to 1.12) for other incidence measures.

CONCLUSION: Our analysis indicates that for objective outcomes, there is no systematic difference between effect estimates from RRCTs and CRCTs.