Background: Although missed and delayed diagnoses have become an important patient safety concern, they remain largely unstudied, especially in the outpatient setting.
Objective: To develop a framework for investigating missed and delayed diagnoses, advance understanding of their causes, and identify opportunities for prevention.
Design: Retrospective review of 307 closed malpractice claims in which patients alleged a missed or delayed diagnosis in the ambulatory setting.
Setting: 4 malpractice insurance companies.
Measurements: Diagnostic errors associated with adverse outcomes for patients, process breakdowns, and contributing factors.
Results: A total of 181 claims (59%) involved diagnostic errors that harmed patients. Fifty-nine percent (106 of 181) of these errors were associated with serious harm, and 30% (55 of 181) resulted in death. For 59% (106 of 181) of the errors, cancer was the diagnosis involved, chiefly breast (44 claims [24%]) and colorectal (13 claims [7%]) cancer. The most common breakdowns in the diagnostic process were failure to order an appropriate diagnostic test (100 of 181 [55%]), failure to create a proper follow-up plan (81 of 181 [45%]), failure to obtain an adequate history or perform an adequate physical examination (76 of 181 [42%]), and incorrect interpretation of diagnostic tests (67 of 181 [37%]). The leading factors that contributed to the errors were failures in judgment (143 of 181 [79%]), vigilance or memory (106 of 181 [59%]), knowledge (86 of 181 [48%]), patient-related factors (84 of 181 [46%]), and handoffs (36 of 181 [20%]). The median number of process breakdowns and contributing factors per error was 3 for both (interquartile range, 2 to 4).
Limitations: Reviewers were not blinded to the litigation outcomes, and the reliability of the error determination was moderate.
Conclusions: Diagnostic errors that harm patients are typically the result of multiple breakdowns and individual and system factors. Awareness of the most common types of breakdowns and factors could help efforts to identify and prioritize strategies to prevent diagnostic errors.