Study: 1 in 20 Americans Misdiagnosed

As many as half of the errors may lead to 'severe harm,' researchers say.

At least 5 percent outpatients are incorrectly diagnosed by their doctors, a new study says.

At least 5 percent outpatients are incorrectly diagnosed by their doctors, a new study says.

By + More

Millions of Americans are misdiagnosed by their doctors every year, potentially worsening their illnesses or injuries and posing “a substantial patient safety risk,” a new study finds.

Doctors at outpatient clinics wrongly diagnosed at least one in 20 of their adult patients, amounting to about 12 million people nationwide, according to a study published in the journal BMJ Quality and Safety.

[READ: Physicians Abandon Insurance for 'Blue Collar' Concierge Model]

As many as half of those errors had “the potential to lead to severe harm.”

“Diagnostic errors pose an important threat to health care quality and safety in outpatient settings,” Drs. Hardeep Singh of the Houston Veterans Affairs Center for Innovations in Quality and Eric J. Thomas of the University of Texas at Houston wrote in their paper.

Singh and Thomas analyzed previous research that examined certain patient behaviors: either “unusual patterns of return visits” after an initial exam by a primary care doctor, or lack of any follow-up after “abnormal” findings related to colorectal cancer.

Both behaviors are “suggestive of diagnostic errors,” Singh and Thomas said.

The pair also looked at consecutive cases of lung cancer.

In all of the studies, the doctors found, “diagnostic errors were confirmed through chart review and defined as missed opportunities to make a timely or correct diagnosis based on available evidence,” they wrote.

[ALSO: U.N. Panel: Completely Eliminate Greenhouse Gas Emissions by 2100]

In fact, based on their findings, the misdiagnoses were occurring so frequently that they appeared to affect 5 percent of patients nationwide.

“This foundational evidence should encourage policymakers, health care organizations and researchers to start measuring and reducing diagnostic errors.” Singh and Thomas said. 

Corrected on April 17, 2014: This story has been updated to correct a numerical typo inserted in a quote.