Malpractice Claims of Internal Medicine Involving Diagnostic and System Errors in Japan.

Objectives Medical litigation resulting from diagnostic errors leads to lawsuits that are time-consuming, expensive, and psychologically burdensome. Few studies have focused on internists, who are more likely to make diagnostic errors than others, with assessments of litigation in terms of system and diagnostic errors. This study explored factors contributing to internists losing lawsuits and examined whether system or diagnostic errors were more important on the outcome. Methods Data regarding 419 lawsuits against internists closed between 1961 and 2017 were extracted from a public Japanese database. Factors affecting litigation outcomes were identified by comparative analysis focusing on system and diagnostic errors, environmental factors, and differences in initial diagnoses. Results Overall, 419 malpractice claims against internists were analyzed. The rate of lawsuits being decided against internists was high (50.1%). The primary cause of litigation was diagnostic errors (213, 54%), followed by system errors (188, 45%). The foremost initial diagnostic error was "no abnormality" (17.2%) followed by ischemic heart disease (9.6%) and malignant neoplasm (8.1%). Following cause-adjustment for loss, system errors were 21.37 times more likely to lead to a loss. Losses were 6.26 times higher for diagnostic error cases, 2.49 times higher for errors occurring at night, and 3.44 times higher when "malignant neoplasm" was the first diagnosis. Conclusions This study found that system errors strongly contributed to internists' losses. Diagnostic errors, night shifts, and initial diagnoses of malignant neoplasms also significantly affected trial outcomes. Administrators must focus on both system errors and diagnostic errors to enhance the safety of patients and reduce internists' risk exposure.