A new data analysis from Morris Wilson Knepp Jacquette, P.C., produced in partnership with 1Point21 Interactive, finds that an estimated 7.4 million diagnostic errors occur in U.S. emergency departments each year. Of those, 2.6 million result in preventable harm, and 371,000 lead to serious outcomes including permanent disability or death.
The analysis draws on a 2022 systematic review published in the National Center for Biotechnology Information and medical malpractice claim data from the Controlled Risk Insurance Company’s Comparative Benchmarking System, one of the largest malpractice databases in the country.
Key Findings
- Roughly 1 in 18 emergency room visits involves at least one diagnostic error, an error rate of approximately 5.7% across an estimated 130 million annual U.S. ER visits.
- Stroke carries a 17% overall miss rate in emergency departments, a figure that climbs to 40% when the presenting symptom is dizziness or vertigo rather than the more recognizable weakness or facial drooping.
- Aortic aneurysm and dissection are missed in an estimated 28% of cases, making them among the most frequently overlooked vascular emergencies.
- Three condition categories, vascular events, infections, and cancers, account for 75.8% of all serious misdiagnosis-related harms across care settings. Infections alone represent 34% of serious harm cases.
- Spinal and intracranial abscess carries the highest estimated miss rate at 62%, with one study finding that 68% of patients required multiple ER visits before receiving a correct diagnosis.
“The variation we see in miss rates across hospitals and symptom presentations tells us that a meaningful share of these errors are preventable,” said a senior research strategist involved in the analysis. “A stroke presenting as dizziness is the same stroke as one presenting with arm weakness. The gap in detection rates reflects a gap in clinical pattern recognition, not in the condition itself.”
Why This Matters
The findings highlight a structural tension in emergency medicine: conditions that present atypically, either in younger patients, women, or with uncommon symptoms, are consistently more likely to be missed. Stroke misdiagnosis rates among women are higher in part because women are more likely to present with non-classic symptoms such as confusion, shortness of breath, or hiccups. Similarly, 89% of diagnostic error malpractice claims in the 2022 review involved failures in clinical judgment, most often attributed to atypical case presentations rather than outright negligence.
For patients, the practical implication is clear. A missed diagnosis on a first ER visit does not foreclose a correct one. When symptoms persist or worsen after discharge, continued care-seeking is important. For conditions in the “Big Three” categories, the window between a missed diagnosis and a serious outcome can be measured in hours.
Methodology
The analysis relies primarily on a systematic clinical review of diagnostic errors in emergency medicine published via the National Center for Biotechnology Information. Supporting data on malpractice claim frequency was drawn from the CRICO Comparative Benchmarking System. Miss rates are derived from retrospective chart analyses in which patient records were reviewed to assess diagnostic accuracy. The full analysis is available at morriswilson.com.
About Morris Wilson Knepp Jacquette, P.C.
Morris Wilson Knepp Jacquette, P.C. is a Philadelphia medical malpractice law firm representing patients and families harmed by preventable diagnostic and treatment errors. The firm offers free consultations for individuals who believe they or a family member received a delayed or incorrect diagnosis that led to serious harm.
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