Choosing wisely between randomized controlled trials and observational designs in studies about interventions

Abstract

Randomized controlled trials (RCTs) are the gold standard for evaluating the efficacy of interventions, because they avoid key sources of bias by randomly allocating participants to the treatment or control. That feature of the study design makes RCTs the highest ranked type of study within the Evidence-Based Medicine framework grading system. However, not all questions about health interventions can be answered with an RCT. Observational studies may be more appropriate to study certain aspects about interventions and thus complement RCTs. In some situations, it is unfeasible or unethical to randomize patients to a treatment, such as a surgical intervention, if surgeons are uncomfortable performing an unfamiliar procedure. In addition, observational studies are better suited to evaluate the incidence of adverse events of interventions because they have less strict inclusion and exclusion criteria, which allows a broader spectrum of the target population to be included. While RCTs are usually the best option to test efficacy (the effect of the intervention under ideal conditions), observational studies are a valuable option to evaluate effectiveness (the effect of an intervention in real life).