An estimated 1 in 20 U.S. adults could be misdiagnosed during outpatient visits, and about half of those errors could prove to be harmful for the patient, finds a new study in the journal BMJ Quality and Safety.

Misdiagnoses remain a major problem, health care quality and safety experts say, one that is often overlooked and underfunded.

Researchers hoping to estimate the frequency of misdiagnoses — which they defined as “missed opportunities to make a timely or correct diagnosis based on the available evidence” — analyzed data from three previous studies on U.S. outpatients. Findings from the studies were combined and extrapolated to the general population.

The analysis looked at triggers which detected unusual patterns of return visits and hospitalizations, and lack of timely follow-up for patients who were later diagnosed with disease.

More than 5%, or about 12 million U.S. adults, could be misdiagnosed during an outpatient visit, the researchers concluded, and about one-half of these errors had the potential to lead to worse outcomes for the patients.

“The numbers are a bit surprising when you put it at the population level, said Dr. Hardeep Singh, lead author of the study and a researcher at the Veterans Affairs Center for Innovations in Quality, Effectiveness and Safety, based in Houston. “Diagnostic errors have been difficult to measure, but when you put these findings in context with the emerging evidence about this problem over the past few decades, it really makes sense.”

%%BREAK%%

One of the studies used in the analysis, published in March 2013 in JAMA Internal Medicine, identified nearly 70 different conditions for which misdiagnoses occurred in the primary care setting, like pneumonia, renal failure and urinary tract infections. The other two focused specifically on cancer, including a retrospective study published in BMJ that used electronic health-record data to detect potential delays in prostate and colon cancer diagnoses; and a 2010 study in the Journal of Clinical Oncology, which evaluated whether EHRs could be good predictors of misdiagnoses in lung cancer.

The reasons for the high numbers of “missed opportunities” are multifaceted, experts who spoke with Modern Healthcare explained. They cited concerns around various items within the healthcare setting, like the structure of outpatient systems, cognitive biases and unclear clinical guidelines. It will take more than one approach to make improvements.

“This is a hidden problem,” said Dr. David Newman-Toker, director of initiatives for diagnostic safety and quality with the Armstrong Institute for Patient Safety and Quality at Johns Hopkins Medicine, Baltimore. He agreed with the authors, who said the study's limitations may mean the numbers of misdiagnoses might be underreported.

“Although this may numerically be the biggest patient-safety problem, it's the bottom of the iceberg,” he said. Efforts to make improvements in other areas — like wrong-side surgeries and hospital acquired infections — have really taken off, but there is very little reporting on diagnostic error, Dr. Newman-Toker explained.

Others pointed to concerns with the way primary care is structured in the U.S. health care system.

%%BREAK%%

“Doctors just don't have much time,” said Dr. Otis Brawley, chief medical officer for the American Cancer Society.

Physicians often have eight to 10 minutes to make clinical decisions, he says, and are therefore forced to make decisions without complete information or with incompletely digested information. For example, colon cancer can easily be missed initially, he said, because patients often show up with symptoms like a stomach ache or diarrhea, which can be associated with other conditions.

“The pressure to move patients in and out and the resulting brief clinical interactions between doctor and patients is a situation that fosters medical errors,” Dr. Brawley said.

Unclear guidelines and limited diagnostic options, might also present challenges that lead to some frequently misdiagnosed conditions.

“With regard to lung cancer, early detection is our biggest problem,” explained Dr. Norman Edelman, senior medical adviser for the American Lung Association. CT scans are better at identifying potential lung tumors than routine chest X-rays, Dr. Edelman said, but every nodule that might be identified on a scan should not be biopsied.

“You'd be doing an invasive procedure on too many people,” he said. “That would be overdiagnosis.”

Efforts to measure and reduce diagnostic errors should be a bigger focus for policymakers, healthcare organizations and researchers, the authors of the new report conclude. The difficulty, Dr. Singh said, is that it takes multiple factors working together to make the improvements.

%%BREAK%%

Concerns over the lack of focus on diagnostic errors were shared by many of the experts, including Dr. Newman-Toker.

“It's one thing to sound the alarm, but we're talking about potentially preventable misdiagnoses. There was a chance to do things differently,” he said.

Diagnostic errors accounted for the largest fraction of malpractice claim payouts, amounting to $38.8 billion between 1986 and 2010, according to a study he authored last spring.

“This is an issue that merits a lot more attention than it has gotten,” he said. “It's a major public health problem.”

Sabriya Rice writes for Modern Healthcare, a sister publication of Business Insurance.