Estimation of the number of patient deaths recognized by a medical practitioner as caused by adverse events in hospitals in Japan: A cross-sectional study

Chart reviews have been used to assess the incidence and impact of adverse events, but most of them are not a nationally representative sample. In addition, the definition of adverse events is generally broad and covers unintended events; the relationship to outcome is often unclear, and official estimates have not matched those of medical practitioner's recognition. The number of patient deaths from adverse events remains unknown. This study aimed to investigate the number of adverse event related patient deaths and mortality rate as recognized by medical practitioners in Japan, and to reveal the applicability of our method for estimating the number of adverse event related patient death as an alternative to a chart review. In 2015, a mail survey of 3270 hospitals asked how many patient deaths had been caused by adverse events at the hospital in the last 3 years. The hospitals were selected by stratified random sampling according to the number of beds. The number of patient deaths caused by adverse events and the mortality rate were estimated, with adjustments for the hospital type and the number of beds. The mail survey response rate was 22.4% (731/3270). The number of patient deaths caused by adverse events in a year was estimated to be between 1326 and 1433. The mortality rate was estimated at 8.81 to 9.52 cases per 100,000 discharged patients, and 2.65 to 2.87 cases per 1,000,000 person-days. The mortality rate was high at acute care hospitals with ≥500 beds and at psychiatric hospitals. The nationwide number of patient deaths recognized by medical practitioners as caused by adverse events and its mortality rate were estimated. In comparison with a chart review, a mail survey was a faster and a cheaper way, and was able to cover a wide range of hospitals for estimating mortality rate of adverse events.