A new study from the Agency for Healthcare Research and Quality (AHRQ) estimates that over 7 million people may be inaccurately diagnosed in hospital EDs every year, and around 370,000 patients suffer serious harm from these misdiagnoses, but some health experts are calling into question the study's methods.

Study details and key findings

For the study, researchers from Johns Hopkins University, who were under contract with AHRQ, analyzed data from 279 studies published between January 2020 and September 2021 to determine the prevalence and effect of diagnostic errors in the ED. Although many of the studies were conducted outside of the United States, the researchers noted that they were in "developed countries deemed comparable by a technical expert panel."

Based on the analysis, the researchers estimated that 7.4 million patients (5.7%) are misdiagnosed during 130 million ED visits every year. As a result, around 2.6 million (2.0%) suffer an adverse event, around 370,000 suffer serious harm, and around 250,000 (0.2%) die.

Stroke, myocardial infarction, aortic aneurysm/dissection, spinal cord compression/injury, and venous thromboembolism were the top five diseases associated with serious misdiagnosis-related harms, making up 39% of all cases. Other diseases in the top 15 included lung cancer, spinal and intracranial abscess, and traumatic brain injury.

According to the researchers, nonspecific or atypical symptoms often increased the likelihood of a misdiagnosis. For example, physicians may not immediately think of a spinal abscess when a patient is complaining of back pain or a heart attack when a younger patient is experiencing shortness of breath.

The researchers also found that diagnostic error rates varied across demographics, with women and people of color having a roughly 20% to 30% higher risk of being misdiagnosed.

Overall, the estimated rate of misdiagnoses in the ED is relatively low "and consistent with what has been found in other clinical settings," but these errors are still a "critically important patient safety concern," the researchers wrote.

"This is the elephant in the room no one is paying attention to," David Newman-Toker, the director of Johns Hopkins' Armstrong Institute Center for Diagnostic Excellence and one of the study's authors.

Experts push back on study results

According to the New York Times, several medical organizations criticized the study after its release, largely due to its reliance on data from European countries and Canada instead of the United States.

"In addition to making misleading, incomplete and erroneous conclusions from the literature reviewed, the report conveys a tone that inaccurately characterizes and unnecessarily disparages the practice of emergency medicine in the United States," said Christopher Kang, the president of the American College of Emergency Physicians (ACEP).

According to Kang, the researchers' use of studies from outside the United States may have distorted the findings and led to the number of misdiagnoses being overestimated. "While most medical specialties have similar training in Western nations, emergency medicine does not," he said.

In response, the study's authors have acknowledged a need for more research specifically on EDs in the United States. "We need studies done in the United States," said Susan Peterson, an emergency medicine physician at Johns Hopkins and one of the study's authors. "It's a huge gap in the literature."

Other experts expressed concerns regarding how the study extrapolated its 0.2% fatality rate attributed to ED misdiagnoses.

In a joint letter signed by multiple health groups, including ACEP, the American Academy of Emergency Medicine, and the American Board of Emergency Medicine, the groups noted that the 0.2% fatality rate "is extrapolated to imply 250,000 preventable deaths annually in the U.S., placing this outcome as the third leading cause of death (fourth during Covid)."

However, this extrapolation "stems from a single study, undertaken nearly two decades ago with data from a relatively small sample of patients drawn from the high acuity are of an ED in an academic center in Canada, in which a single patient died," the groups wrote. "It is not clear if the 'missed diagnosis' in this case was evidence to the inpatient admitting team or was only discerned later during the inpatient stay."

In a report for Inside Medicine, Jeremy Faust, an emergency physician, wrote that if the study's fatality rate is correct, that would mean "that 8.6% of all deaths in the United States—that is, 250,000 out of 2.9 million deaths (2019, the last pre-pandemic year)—are caused by mistakes and misses in ERs. That's preposterous, on its face."

Faust added the paper does not focus on the dangers of over-diagnosis. The only way to catch every medical issue "would be to hospitalize hundreds, or thousands, or even tens-of-thousands … But doing that would cause more harm than good because a small number of those patients would die of complications from what were overly aggressive invasive procedures, or from hospital-acquired infections, or falls, etc."

In addition, health experts noted that while the AHRQ study focuses on EDs, misdiagnoses are a problem among all doctors.

"The bottom line is diagnosis is hard," said Doug Salvador, an infectious disease specialist who is the board president of the Society to Improve Diagnosis in Medicine and the chief quality officer at Baystate Health.

The study is "not about laying the blame on the feet of emergency room physicians," Newman-Toker said. Instead, the findings emphasize a need to look more closely at where diagnostic errors are being made as a whole and what can be done to prevent them.

Experts also noted that simply doing more testing will not be enough to prevent misdiagnoses. "This is a really complicated calibration problem," said Robert Wachter, chair of medicine at the University of California, San Francisco. "The answer can't be let's test everybody for all this stuff all the time."

Overall, reducing misdiagnoses and the harms they can potentially cause patients is "is going to have to be a sustained effort, and that requires resources and support," Newman-Toker said. (Abelson, New York Times, 12/15; Carbajal, Becker's Hospital Review, 12/15; AHRQ report, 12/15; Faust, Inside Medicine, 12/16)