Studies: 21% of people with serious conditions are misdiagnosed; most in U.S. will get an incorrect or late diagnosis at some time

More than one in five patients who sought a second opinion at the Mayo Clinic had been misdiagnosed by their primary-care doctors, a study concluded.

The results, published in the Journal of Evaluation in Clinical Practice, "are generally similar to other research on diagnostic error, but provide additional evidence for advocates who say such findings show that the health-care system still has room for improvement," Lenny Bernstein reports for The Washington Post.

Researchers at Mayo, in Rochester, Minn., looked back at 286 patients their primary-care doctors and nurse practitioners saw in 2009 and 2010. Nearly two-thirds were under 65, and most were female. The researchers reported that in 62 cases (21 percent), the second diagnosis was "distinctly different" from the first. In 188 cases, the diagnoses were at least partly correct but were “better defined” by the second opinion, the study said. In 36 cases, the diagnoses were the same.

Mark Graber, a senior fellow at the research institute RTI International and founder of the Society to Improve Diagnosis in Medicine, told Bernstein, “Diagnosis is extremely hard. There are 10,000 diseases and only 200 to 300 symptoms.”

Graber, who was not involved in the Mayo research, "estimates that the rate of misdiagnosis, although difficult to determine, occurs in 10 percent to 20 percent of cases," Bernstein reports. The new study cites previous research that found diagnostic errors "contribute to approximately 10 percent of patient deaths" and "account for 6 to 17 percent of adverse events in hospitals."

"In 2015, the National Academy of Medicine reported that most people will receive an incorrect or late diagnosis at least once in their lives, sometimes with serious consequences," Bernstein writes. "It cited one estimate that 12 million people — about 5 percent of adults who seek outpatient care — are misdiagnosed annually. The report also noted that diagnostic error is a relatively under-measured and understudied aspect of patient safety."

James Naessens, a policy researcher at Mayo, said in a press release: "Effective and efficient treatment depends on the right diagnosis. Knowing that more than one out of every five referral patients may be completely [and] incorrectly diagnosed is troubling — not only because of the safety risks for these patients prior to correct diagnosis, but also because of the patients we assume are not being referred at all."