Incidence, contributing factors, and predictors of diagnostic errors in medical inpatients: A retrospective cohort study.

Background Diagnostic error is a major patient safety concern in hospitals, yet most studies have focused on selected high-risk subgroups, leaving the broader general internal medicine inpatient population understudied. Objectives To determine the incidence, contributing factors, resulting harm, and predictors of diagnostic error in medical inpatients.Methods This retrospective cohort study included adults admitted to internal medicine between 01/2022 and 12/2022 at one tertiary and 4 secondary care hospitals in Switzerland. Retrieved admissions were randomly ordered, and electronic medical records were reviewed sequentially by two clinicians using standardized instruments, until reaching a pre-specified target threshold of 50 patients with ≥1 diagnostic error, enabling analysis of five predictors. The primary outcome was the occurrence of a diagnostic error. The secondary outcome was the resulting level of harm. Five pre-specified predictors were analyzed using multivariable logistic regression. Results Of 347 patients (median age 73 [interquartile range, 61-81] years; 140 [40.3%] female), 52 (15%; 95% confidence interval [CI], 11.6%-19.1%) experienced ≥1 diagnostic error, causing harm in 43/52 patients (82.7%; 95% CI 70.3%-90.6%). The most common contributing factors were failures to consider the correct diagnosis (40/52, 76.9%), order appropriate tests (31/52, 59.6%), and act on critical physical exam findings (30/52, 57.7%). Neurocognitive/psychiatric disorders (odds ratio [OR], 2.20; 95% CI, 1.20-4.10) and active cancer (OR, 2.10; 95% CI, 1.01-4.20) independently predicted diagnostic error. Conclusions Diagnostic error is common among adult medical inpatients and causes harm. We identified neurocognitive/psychiatric disorders and active cancer as patient-level predictors of diagnostic error, providing a basis for future studies on targeted interventions.