International and global issues – differences in health systems, patient populations, and medical practice

Abstract Health care systems and medical practices are heterogeneous across the globe, which may relate to differences in socioeconomic statuses, approval timelines and access to innovative therapies, screening and treatment guidelines, genetic variations, languages, and cultures in different countries and regions. The distribution of disease risk factors; availability and development status of various data sources including electronic health records, medical claims, and national registry databases; data linkage and coding algorithms for exposures and outcomes; and regulations on patients’ privacy, may also vary significantly across the regions or countries. In this Chapter, we review the heterogeneity of these topics, summarize the available data sources in different regions, and provide details of different coding algorithms used in different data sources. We also provide examples of these differences in oncology, psychiatry, and vaccines disease areas. Researchers should be aware of these differences when planning or implementing international pragmatic randomized trials.