Novel Framework (Target Trial Emulation) in Observational Causal Inference Research Based on Real-world Data and Its Application Prospects in Traditional Chinese Medicine

"Target trial emulation" (TTE), as a new framework in real-world research, has been formally established in recent years. It can be used to guide the evaluation of the effectiveness and safety of medical interventions based on real-world data for observational causal inference. The core idea of this framework is to follow the principles of randomized controlled trial (RCT), emulate a corresponding RCT using real-world data, and then draw conclusions about the causal relationship between interventions and outcomes. The main implementation tips of TTE can be summarized as "3-7-2": 3 implementation steps including formulating the causal question, designing the emulation plan, and emulating the target study; 7 design elements including eligibility criteria, treatment strategies, intervention allocation, follow-up period, outcome, causal contrast of interest, and analysis plan; and control of 2 critical biases including immortal time bias and prevalent user bias. In this article, we present an overview of the development, current status, implementation steps, classic examples, advantages and limitations of TTE, and its application prospects in traditional Chinese medicine (TCM). It is hoped that this article can assist researchers in TCM to utilize this method for real-world research and contribute to the construction of a clinical evaluation system with distinctive features of TCM.