Clinical research using real-world data: A narrative review.

Randomized controlled trials (RCTs) and studies using real-world data (RWD) each have their strengths and weaknesses, and can effectively complement each other. When RCTs are not feasible, RWD studies offer a valuable alternative. In this narrative review, we examine several types of RWD studies, focusing on studies utilizing administrative claims databases. These include the Diagnosis Procedure Combination databases, commercially available health checkups and healthcare claims databases (such as the JDMC and DeSC databases), and the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). Given that these claims databases cover different populations, patient settings, variables, and levels of accessibility, it is crucial for researchers to select the most appropriate data source to effectively address their research questions. Additionally, it is desirable for readers of studies using these databases to be aware of their characteristics in order to fully understand the context and limitations of the research findings.