Target Trial Emulation or Target Trial Approximation?

Abstract

Target trial emulation has contributed to improvements in the design and interpretation of observational studies aimed at causal inference. By encouraging researchers to think explicitly about the design of a hypothetical randomized trial, it has helped identify and address avoidable design flaws. However, the framework cannot overcome biases and limitations inherent in observational data. Despite the aim of emulating a randomized trial, observational data cannot reproduce random treatment assignment or blinding, and may not necessarily provide greater generalizability than a randomized trial. Thus, the term "emulation" may imply a degree of similarity to a randomized trial that observational data cannot realistically achieve and deserves critical reconsideration to better reflect the limitations of observational data. Target trial emulation has helped improve how observational studies are designed and interpreted. However, observational data still have important limitations and biases that cannot be fully overcome. The term “emulation” may suggest that observational studies can closely reproduce randomized trials, when in practice they can only approximate them.