As the Japanese health insurance system is reimbursed on a fee-for-service basis, the claims data are useful sources for quantitative analysis on practice and prescription patterns as well as the health care resource use. However, the claims database has limitations such as incomplete description of the patients' condition and severity, and the lack of prescription data for low-priced drugs.
For use in pharmacoepidemiologic studies, patient information from medical charts, prescription forms, and/or hospital information systems may need to be included to compensate for the limitations of the claims data.