Analysis: One in Three Malpractice Cases with Serious Patient Harms Are Due to Misdiagnosis

Cancer, vascular events, and infection account for three-fourths of high-harm, diagnosis-related claims

Washington, DC – (July 11, 2019) One-third (34%) of malpractice cases that result in death or permanent disability stem from an inaccurate or delayed diagnosis, making it the number one cause of serious harms among medical errors, according to a study appearing in the peer-reviewed journal Diagnosis.

Researchers from the Johns Hopkins University School of Medicine and CRICO Strategies analyzed more than 55,000 malpractice claims from CRICO Strategies’ CBS database (Comparative Benchmarking System) to determine how many were attributable to diagnostic error. The research was funded by the Society to Improve Diagnosis in Medicine (SIDM) through a grant from the Gordon and Betty Moore Foundation.

Of malpractice claims attributable to diagnostic error, researchers reviewed underlying disease states to identify patterns of misdiagnosis. They found that of the diagnostic errors causing the most harm, three quarters (74.1%) are attributable to just three categories of conditions: cancer (37.8%), vascular events (22.8%), and infection (13.5%). These severe cases resulted in $1.8 billion in malpractice payouts over 10 years. The authors also showed that, collectively, the top five in each category account for nearly half (47.1%) of all the serious harms.

“It is not just inconvenient to have a wrong or delayed diagnosis. For many patients, misdiagnosis causes severe harm and expense, and in the worst cases, death,” said David Newman-Toker, MD, PhD, professor of neurology at the Johns Hopkins University School of Medicine and director of the Johns Hopkins Armstrong Institute for Patient Safety and Quality’s Center for Diagnostic Excellence, who served as lead author of the research. Dr. Newman-Toker also is President of the Board of SIDM. “If we’re going to reduce serious harms from medical errors, major strides must be made to improve diagnostic accuracy and timeliness. This study shows us where to focus to start making a difference for patients. It tells us that tackling diagnosis in these three specific disease areas could have a major impact on reducing misdiagnosis-related harms.”

The research confirms that inaccurate or delayed diagnosis remains the most common, most catastrophic and most costly of medical errors. The analysis provides additional context for a 2015 National Academy of Medicine report that highlighted that diagnostic errors result in up to 80,000 deaths annually in U.S. hospitals.

Neither the blame nor the onus to improve diagnosis rests solely on the shoulders of individual physicians, the researchers stressed, saying that it will take system-wide efforts, including the involvement of patients and their families, among others. They also noted that research and quality improvement efforts need to focus on interventions in the specific practice settings where the harm occurs such as “stroke in the emergency department, sepsis in the hospital, and lung cancer in primary care.”

“This work showcases that myriad factors contribute to missed and delayed diagnosis and highlights the need for further collaboration across the healthcare system to significantly improve diagnosis and ensure the best possible outcomes for patients,” said Paul L. Epner, chief executive officer and co-founder of SIDM. “The complexity of the diagnostic process and the collaborative approaches needed to improve accuracy mean change will not occur overnight.”

One effort to address the multi-faceted problem of diagnostic error is the ACT for Better Diagnosis™ initiative of SIDM. Working as part of a coalition, more than 50 national organizations representing health systems, patients and families, clinicians, risk managers, testing professionals, and others have publicly committed to and described work on initiatives to improve diagnostic quality and safety.


The researchers sought to identify diseases accounting for the majority of serious misdiagnosis-related harms (morbidity/mortality). Diagnostic error cases were identified from CRICO Strategies’ Comparative Benchmarking System database (2006-2015), representing 28.7 percent of all U.S. malpractice claims. Diseases were grouped according to the Agency for Healthcare Research and Quality’s Clinical Classifications Software that aggregates International Classification of Diseases diagnostic codes into clinically sensible groupings. The researchers analyzed vascular events, infections, and cancers, including frequency, severity, and settings. High-severity harms were defined by scores of 6-9 (serious, permanent disability or death) on the National Association of Insurance Commissioners Severity of Injury Scale.

# # #
About the Society to Improve Diagnosis in Medicine (SIDM)
The Society to Improve Diagnosis in Medicine catalyzes and leads change to improve diagnosis and eliminate harm from diagnostic error. We work in partnership with patients, their families, the healthcare community and every interested stakeholder. SIDM is the only organization focused solely on the problem of diagnostic error and improving the accuracy and timeliness of diagnosis. In 2015, SIDM established the Coalition to Improve Diagnosis to increase awareness and actions that improve diagnosis. Members of the Coalition represent hundreds of thousands of healthcare providers and patients—and the leading health organizations and government agencies involved in patient care. Together, we work to find solutions that enhance diagnostic safety and quality, reduce harm, and ultimately, ensure better health outcomes for patients. Visit to learn more.

Press Inquiries?
More About the Study

Research appearing in the peer-reviewed journal Diagnosis shows that inaccurate and delayed diagnoses remain the most common, most catastrophic, and most costly of serious medical errors.