Abstract
The medical payment system based on Diagnosis Procedure Combination (DPC), which is a Japanese prospective payment system, was introduced in April 2003. By July 2010, 1,391 hospitals, which cover 18.0% of all hospitals, implemented this DPC-based payment system. The Ministry of Health, Labor and Welfare periodically conducts an impact assessment survey (hereafter referred to as a DPC survey) at those hospital to update DPC classification categories and also determine, for instance, payment weight and hospital adjustment factors. To each DPC survey, the hospitals report patients' medical data, which should be pseudonymized by certain pseudonymization methods according to the ministry's guideline.
We surveyed DPC-based hospitals in a prefecture and conclude that 31.4% of hospitals have failed to pseudonymize personal data when reporting them to DPC surveys. We find security vulnerabilities and privacy concerns in the current DPC survey system. Moreover, we propose a way to make the survey system safer in the future.
