Reporting of Observational Studies Explicitly Aiming to Emulate Randomized Trials: A Systematic Review.

Importance: Observational (nonexperimental) studies that aim to emulate a randomized trial (ie, the target trial) are increasingly informing medical and policy decision-making, but it is unclear how these studies are reported in the literature. Consistent reporting is essential for quality appraisal, evidence synthesis, and translation of evidence to policy and practice. Objective: To assess the reporting of observational studies that explicitly aimed to emulate a target trial. Evidence Review: We searched Medline, Embase, PsycINFO, and Web of Science for observational studies published between March 2012 and October 2022 that explicitly aimed to emulate a target trial of a health or medical intervention. Two reviewers double-screened and -extracted data on study characteristics, key predefined components of the target trial protocol and its emulation (eligibility criteria, treatment strategies, treatment assignment, outcome[s], follow-up, causal contrast[s], and analysis plan), and other items related to the target trial emulation. Findings: A total of 200 studies that explicitly aimed to emulate a target trial were included. These studies included 26 subfields of medicine, and 168 (84%) were published from January 2020 to October 2022. The aim to emulate a target trial was explicit in 70 study titles (35%). Forty-three studies (22%) reported use of a published reporting guideline (eg, Strengthening the Reporting of Observational Studies in Epidemiology). Eighty-five studies (43%) did not describe all key items of how the target trial was emulated and 113 (57%) did not describe the protocol of the target trial and its emulation. Conclusion and Relevance: In this systematic review of 200 studies that explicitly aimed to emulate a target trial, reporting of how the target trial was emulated was inconsistent. A reporting guideline for studies explicitly aiming to emulate a target trial may improve the reporting of the target trial protocols and other aspects of these emulation attempts.

Baseline imbalance and heterogeneity are present in meta-analyses of randomized clinical trials examining the effects of exercise and medicines for blood pressure management.

Randomized clinical trials attempt to reduce bias and create similar groups at baseline to infer causal effects. In meta-analyses, baseline imbalance may threaten the validity of the treatment effects. This meta-epidemiological study examined baseline imbalance in comparisons of exercise and antihypertensive medicines. Baseline data for systolic blood pressure, diastolic blood pressure, and age were extracted from a network meta-analysis of 391 randomized trials comparing exercise types and antihypertensive medicines. Fixed-effect meta-analyses were used to determine the presence of baseline imbalance and/or inconsistency. Meta-regression analyses were conducted on sample size, the risk of bias for allocation concealment, and whether data for all randomized participants were presented at baseline. In one exercise comparison, the resistance group was 0.3 years younger than the control group (95% confidence interval 0.6 to 0.1). Substantial inconsistency was observed in other exercise comparisons. Less data were available for medicines, but there were no occurrences of baseline imbalance and only a few instances of inconsistency. Several moderator analyses identified significant associations. We identified baseline imbalance as well as substantial inconsistency in exercise comparisons. Researchers should consider conducting meta-analyses of key prognostic variables at baseline to ensure balance across trials.