Project Summary/Abstract Traditional randomized controlled trials (RCTs) are the gold standard for assessing the efficacy of treatments. However, RCTs may have missing data, may not capture all effectiveness and safety outcomes that are important to patients, may have limited follow-up duration, and their results may not always generalizable to diverse patient populations in real-world settings. Linking RCTs to real-world data (RWD), such as insurance claims and electronic health record, provides a valuable opportunity to enhance traditional RCTs by addressing these shortcomings. In this project, we propose linking RCTs to participants’ RWD using two case studies: The INfluenza Vaccine to Effectively Stop Cardio Thoracic Events and Decompensated Heart Failure (INVESTED) trial and Dapagliflozin Evaluation to Improve the LIVEs of Patients With PReserved Ejection Fraction Heart Failure (DELIVER) trial. The overarching objective of this project is to use linked RCT-RWD to develop and validate methods that can enrich both randomized and non-randomized comparative effectiveness studies. We will use linked RCT-RWD to accomplish the following specific aims: Aim 1. To enhance RCT findings using long-term, validated, RWD-based outcome measures. Aim 2. To develop methods for using RWD to replace or impute missing RCT data. Aim 3. To generalize RCT results to broader patient populations in real-world setting. Aim 4: To develop methods to identify sources of discrepant results between RCTs and RWD-based studies.