Extending Inferences from Randomized Clinical Trials to Target Populations Using Observational Data: A Scoping Review of Transportability Methods

Objective: Randomized clinical trial (RCT) results often define clinical decision making, but the highly curated populations of trails, and the rigorous methodology utilized, are often not reflective of real-world practice. The objective of this scoping review is to identify the ability of practical methods to transport findings from randomized clinical trials (RCTs) to target populations. Study design: A scoping review was conducted on the literature regarding transportability from RCTs to observational data cohorts. Each study was assessed for the transportability methodology used, and to what degree the RCT treatment effect (estimated target parameter) was seen in the target population (intended patients) in observational data. Results: A total of 15 published papers were included. The research topics include cardiovascular diseases, infectious diseases, psychiatry, oncology, orthopedics, anesthesiology, and hematology. These studies show that the outcomes from RCTs could be extended to real-world settings, with varying degrees of effect size and precision. However, in some cases, the estimated target parameters for the target population were statistically significantly different from those in clinical trials. Conclusion: Despite variations in the magnitude of effects between RCTs and real-world studies, transportability methods can play an important role in effectively bridging the gap between clinical research and practical healthcare applications, offering valuable insights for evidence-based medicine.