Data Source

The Diagnosis Procedure Combination (DPC) database, a Japanese nationwide inpatient database, contains administrative claims data and discharge abstracts. For each patient, the DPC includes the main diagnosis, comorbidities at admission, and complications after admission, coded using the corresponding International Classification of Diseases (ICD)-10 codes; surgical interventions and medical procedures, with the original Japanese codes; patient characteristics (age, sex, weight, height, Brinkman index); drugs and devices used during hospitalization; type of hospital (academic or nonacademic); admission status (with or without disturbance of consciousness); and discharge status. The database also includes information on the dates for each drug administered or procedure performed.

All 82 academic hospitals across Japan are obliged to participate in the DPC database, while community hospitals participate voluntarily. The number of included patients in 2012 was over 6.8 million from approximately 1000 hospitals, representing more than half of all inpatient admissions to acute care hospitals across Japan. The data collection period was 6 months (July 1 to December 31) in 2010 and was extended to the entire year (12 months) beginning in 2011. The codes corresponding to each surgery, clinical procedures, and medication are almost complete because they are compulsory items for reimbursement of healthcare costs. The responsible physicians are required to record the information on each patient with reference to each patient's medical chart to maximize the accuracy of these data. The details of the database are described elsewhere.¹⁰