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.