Synthesizing the results of three separate studies, researchers from Houston Veterans Affairs Medical Center and Baylor College of Medicine calculate that 12 million Americans a year, or more than 5 percent of all patients, are misdiagnosed as a result of doctors failing to follow up on “red flags” for cancer and other serious illness.
“We estimate the frequency of diagnostic error to be at least 5% in US outpatient adults, a number that entails a substantial patient safety risk," writes lead author Hardeep Singh, MD, who holds dual appointments in the Section of Health Services Research at Baylor College of Medicine and at the Houston Veterans Affairs Center for Innovations in Quality, Effectiveness and Safety.
"This population-based estimate should provide a foundation for policymakers, healthcare organizations and researchers to strengthen efforts to measure and reduce diagnostic errors."
The study, published online April 17 in BMJ Quality and Safety, The International Journal of Healthcare Improvement, provides only an estimate, based on an extrapolation. Still, it’s an interesting one, particularly when you look at how Hardeep and colleagues came up with it.
And it provides another piece of an already devastating puzzle, coming just months after a study out of Johns Hopkins University found that 160,000 patients a year die or suffer permanent damage as a result of medical error.
Hardeep and team combined data from three previous studies, which they chose because they used similar definitions of what constitutes a medical error. (There is surprising variation in how this term is used.) All three studies involved medical errors that were revealed by a patient’s later diagnosis.
The first study used computer algorithms to detect unusual patterns of return visits after a patient was seen by a primary care doctor. The second study also used electronic algorithms to find lack of follow-up after abnormalities were detected in colorectal cancer screening.
The third study, similar to the second, involved lung cancer cases which did not receive adequate follow-up and treatment after a questionable chest X-ray. “Diagnostic errors were confirmed through chart review and defined as missed opportunities to make a timely or correct diagnosis based on available evidence,” write the authors.
The researchers then combined the results of the studies and extrapolated the rate of outpatient diagnostic error to the entire U.S. adult population, coming up with an annual rate of 5.08%, or approximately 12 million American adults a year.
“Based upon previous work, we estimate that about half of these errors could potentially be harmful,” the authors write.
Looking more closely, the researchers actually came up with three different diagnostic error percentages. For primary care misdiagnoses, the rate was 5.06 percent, while for lung cancer it was just 0.013% and for colorectal cancer an even smaller 0.007 percent. Translated, this means you can probably worry less about doctors missing signs of cancer than signs of other illnesses.
However, the authors note, because even small delays can have a profound effect on the success of cancer treatment, missed cancer diagnoses are the "most harmful and costly types of diagnostic error in the outpatient setting.” In other words, when it comes to cancer, even 0.007 percent is not good.
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