When dealing with urgent medical symptoms, one has to put their health in the hands of the emergency department and trust that they will be correctly diagnosed and treated.
It’s natural to assume that emergency rooms (ERs) always get it right, but the data says otherwise. A 2022 report, Diagnostic Errors in the Emergency Department: A Systematic Review, explores the conditions that commonly get misdiagnosed or go undiagnosed in ERs around the world. Shockingly, millions of patients every year leave the emergency department with the wrong diagnosis, and many suffer serious health consequences as a result.
The attorneys at Morris Wilson Knepp Jacquette, P.C. partnered with 1Point21 Interactive to explore which conditions are being commonly missed, which ones are causing the most harm, and how often these diagnostic errors occur. By examining these patterns, this analysis aims to raise awareness of where diagnostic failures may occur and why follow-up care can be important when symptoms persist.
How Often Do ER Misdiagnoses Happen?
- An estimated 5.7% of all ER visits involve at least one diagnostic error. That’s roughly 1 in 18 visits.
- With 130 million U.S. ER visits per year, that translates to 7.4 million diagnostic errors annually.
- Of those, 2.6 million result in preventable harm, and 371,000 result in serious harm, including permanent disability or death.
Note: Error rate estimates are based on studies from Canada, Spain, and Switzerland; research suggests rates are comparable across the US and Western Europe.
The Most Common Misdiagnoses in the ER
Below are the top 20 misdiagnosed conditions in ERs, grouped by condition category. These conditions are the ones most frequently missed when considering all reported cases, but they do not necessarily have the highest miss rates or cause the most serious harm when missed.
These rankings are derived from medical malpractice claims and incident report data, including data from the Controlled Risk Insurance Company’s (CRICO) Comparative Benchmarking System, one of the largest medical malpractice databases in the country.
Select a body region below to see which conditions are most commonly misdiagnosed.
Fractures
Fractures are the most commonly misdiagnosed condition in ERs, due to the sheer volume of cases. They have a miss rate of just 1%, but because millions of fracture cases are seen in the ER each year, even 1% means tens of thousands of misdiagnoses.
Fractures also rank so high because missed fractures are easy to confirm later; a follow-up X-ray can clearly show what was missed the first time, making these errors more likely to be reported. Fortunately, a missed fracture is rarely life-threatening.
Cardiovascular emergencies
Strokes and heart attacks are the second and third most commonly missed cases in ERs, respectively.
About 17% of stroke cases are initially missed, a figure that jumps to 40% when the stroke presents as dizziness or vertigo. There are roughly 795,000 strokes in the U.S. every year, and with a 17% miss rate, that means an estimated 135,000 strokes may be initially missed in emergency departments annually.
While the total number of missed heart attack cases is high, this is largely due to the sheer volume of people experiencing them. The miss rate is only 1.6%, but with roughly 805,000 cases per year, even a relatively low miss rate results in a substantial number of missed diagnoses (an estimated 12,900). Additionally, reported miss rates vary widely by hospital, ranging from 0% to 29%.
Venous Thromboembolism (VTE) (ranked 5th), aortic aneurysm/dissection (ranked 7th), and arterial thromboembolism (ranked 11th) are the “silent killer” category. These vascular events are often missed because their symptoms can mimic less dangerous conditions.
Cardiac arrhythmia (ranked 19th) often has intermittent symptoms that may not be present during the ER visit, which can lead to a missed diagnosis.
Surgical emergencies
Appendicitis (ranked 4th), ectopic pregnancy/ovarian torsion (ranked 13th), testicular torsion (ranked 15th), GI perforation (ranked 16th), and intestinal obstruction (ranked 20th) are surgical emergencies that often get missed, according to the data.
These are time-sensitive conditions where a delayed diagnosis can mean the difference between a routine procedure and a life-threatening complication. With ectopic pregnancies and testicular torsion, the blood supply is being cut off, making them especially dangerous.
Infections
Missed infections, which can escalate quickly, include meningitis/encephalitis (ranked 8th), sepsis (ranked 9th), and pneumonia (ranked 14th). Infections have a short window for treatment and can have severe consequences if not caught. Unfortunately, many infections present with atypical or subtle symptoms, which can lead to a misdiagnosis.
Spinal and intracranial abscess (ranked 17th), although rare, has the highest estimated miss rate at 62%. This is because an abscess often presents with common symptoms like head or back pain, and it’s so rare that doctors aren’t quick to suggest it as a diagnosis.
Spinal cord and traumatic injuries
Spinal cord compression (ranked 6th), TBI/traumatic intracranial hemorrhage (ranked 10th), and open/non-healing wounds (ranked 18th) can often be missed.
For brain injuries and intracranial bleeds, they can be easy to miss since you can’t see them. In some cases, a patient’s mental state is falsely attributed to intoxication.
Spinal cord compression may be easily missed because back pain, one of its symptoms, is an everyday complaint for many people.
Wounds, while visible and not typically overlooked, can cause different problems. An underlying cause, a retained foreign object, or an infection, may be missed and undertreated.
Cancer
Lung cancer (ranked 12th) is the most commonly misdiagnosed type of cancer. It’s not primarily an emergency room problem; cancer typically requires a full workup done in outpatient settings. In the ER, a nodule or mass may be identified on imaging taken for an unrelated reason, but the finding may be overlooked or never communicated and followed up on.
The 15 ER Misdiagnoses That Cause the Most Serious Harm
Not every misdiagnosis leads to serious health consequences. The top 20 conditions listed in the section above are the most common missed diagnoses, but they aren’t necessarily the most severe when missed. For example, fractures and appendicitis, the two most commonly misdiagnosed conditions, rarely result in permanent harm.
It’s estimated that each year, 371,000 misdiagnoses result in serious harm, which is defined as permanent disability or death. The list below identifies which conditions most often lead to serious harm when not caught in time:
- Stroke
- Myocardial infarction
- Aortic aneurysm and dissection
- Spinal cord compression and injury
- Venous thromboembolism
- Meningitis and encephalitis (tie)
- Sepsis (tie)
- Lung cancer
- Traumatic brain injury
- Arterial thromboembolism
- Spinal and intracranial abscess
- Cardiac arrhythmia
- Pneumonia
- Gastrointestinal perforation and rupture
- Intestinal obstruction
The Big Three
Ten of the fifteen conditions listed above fall into what are called “The Big Three”: Vascular events, infections, and cancers. A 2023 study from the same research team found that these categories of conditions account for 75.8% of serious harm cases when missed (across all care settings, not just emergency departments).
Infections (34%): Infections account for the largest share of serious harms because of how fast they escalate. Examples include sepsis, pneumonia, meningitis, and spinal abscess. If these conditions are not caught in time, a matter of hours can be the difference between life and death.
Vascular Events (28.6%): This is arguably the most dangerous category and includes conditions like stroke, aortic aneurysm/dissection, and myocardial infarction (heart attack). These conditions need to be caught and treated in time, otherwise they could become deadly.
Cancers (13.2%): Cancers account for a smaller share of serious harms overall, but are disproportionately deadly when missed. A delayed diagnosis can mean the difference between catching cancer at an early, treatable stage versus a late stage with a worse prognosis. In the ER specifically, cancers play a smaller role because they are primarily diagnosed in outpatient settings.
Strokes: Different Miss Rates For Different Symptoms
According to the American Heart Association, there are over 795,000 strokes in the United States each year. Yet, the symptoms aren’t always the typical arm weakness and face drooping. Other symptoms like dizziness and headaches are so common that ER doctors often attribute them to less serious conditions.
The overall misdiagnosis rate for stroke is 17%, but it ranges greatly based on symptoms. When patients present with weakness, the rate is only 4%, but jumps up to 40% when the symptoms are dizziness or vertigo.
Demographics also play a role in missed stroke diagnoses. Doctors don’t expect strokes in younger people and women, and women in particular can present with atypical stroke symptoms like shortness of breath, confusion, or hiccups.
Miss Rates By Condition: What the Clinical Research Shows
While the data above comes from medical malpractice claim data, certain conditions have been researched in empirical studies. Although there are certainly limitations to many of these studies, they give us a general idea of misdiagnosis rates.
The Emergency Department (ED) miss rates below are based on clinical studies where patients’ medical files were reviewed by a group of researchers to determine whether each condition was correctly diagnosed during the emergency department visit after the condition was later confirmed.
| Condition | ED Miss Rate | Estimated Range* | Strength of Evidence | Studies Conducted |
| Stroke | 17% | 11% to 23% | High | 19 studies (53,417 participants) |
| Myocardial infarction | 1.6% | 1% to 2% | High | 6 studies (483,611 participants) |
| Aortic aneurysm / dissection | 28% | 22% to 34% | Moderate | 11 Studies (2,735 participants) |
| Venous thromboembolism | 20% | 17% to 24% | Moderate | 3 Studies (2,360 participants) |
| Meningitis / encephalitis | 22% | 18% to 26% | Low | 1 Study (521) participants |
| Sepsis | 19% | 11% to 27% | Moderate | 4 Studies (3,479 participants) |
| Arterial thromboembolism | 15% | 7.9% to 26% | Low | 1 Study (72 participants) |
| Spinal / intracranial abscess** | No data | — | No studies | 0 studies* |
| Pneumonia | 14% | 10% to 20% | Low | 1 Study (180 participants) |
| Appendicitis | 2.5% to 4.8% | — | Moderate | 2 Studies (874 participants) |
| Fractures | 1.0% | 0.9% to 1.2% | Moderate | 13 Studies (136,620 participants) |
| Testicular torsion | 5.3% | 2.7% to 9.3% | Low | 2 Studies (262 participants) |
*Estimated range refers to the Confidence Interval. This means that researchers are 95% confident that the miss rate falls within this range, with the miss rate being their closest estimate.
**Two high-quality spinal abscess studies were excluded from the formal review on technical grounds, but both found miss rates above 55%. One study found that 68% of patients required multiple ER visits before being correctly diagnosed.
Why Do ER Misdiagnoses Happen?
The 2022 Emergency Department study reports that 89% of diagnostic error malpractice claims involved failures in clinical judgment or decision-making. These include errors or delays in diagnostic assessment, lab or image tests ordered, and test interpretation.
These mistakes were most commonly attributed to inadequate clinical knowledge, skill, or reasoning, particularly in atypical case presentations. Atypical in this context includes things like diseases presenting in an uncommon age group, unusual symptoms, or diagnosing a second, third, or fourth condition in an already ill patient. In other words, these mistakes are most common when the symptom or patient doesn’t match the textbook descriptions.
A separate analysis by the Emergency Care Research Institute (ECRI) determined that 70% of diagnostic errors happen during the testing process (ordering, processing, communicating results). They also reported that 12% occurred during monitoring and follow-ups, and 9% during referrals and consultations.
One other potential factor is a shortage of physicians. Data from the Association of American Medical Colleges (AAMC) and the Health Resources and Services Administration (HRSA) show that some states have a much higher rate of doctors to residents than others. Understaffing means less time per patient and more rushed assessments.
What This Means for Patients
This analysis isn’t meant to scare, but to inform. It’s important for people experiencing new medical symptoms to continue seeking medical care if they are not diagnosed correctly the first time.
Although not every diagnostic error results in harm, some have significant consequences. The variation seen across symptoms (strokes) and hospitals (heart attacks) means that many of these errors are preventable.
If you or a family member were sent home from the ER and later learned the diagnosis was wrong or delayed, especially if it resulted in serious harm, it may be worth learning about your options during a free medical malpractice consultation.
Methodology
The majority of the data in this analysis is derived from a National Center for Biotechnology Information (NCBI) clinical review of diagnostic errors in emergency medicine. The underlying studies included in the review are based on retrospective chart analyses, in which researchers examined patient records to assess whether diagnoses made in the emergency department were accurate at the time of care.