“The question is, can we eliminate human error, and the answer is no,” said Hardeep Singh, lead author of the paper, which appeared in the journal BMJ Quality & Safety. “We have just now begun to understand what [these errors] are and what we can do.”

At least 1 in 20 adult outpatients receives an incorrect diagnosis from their doctor, according to a new study. Sometimes the consequences are minor -- calling something an “allergy” when it’s really a cold, for instance. But in more than 6 million patients a year in the United States, such misdiagnosis could have major consequences, such as a dangerous delay in cancer treatment.


The patient, their care teams, and the health care system need to work together to reduce these mistakes, said Singh, a patient safety researcher at the Veterans Affairs Center for Innovations, and Baylor College of Medicine, both in Houston.

Doctors must walk a fine line between missing diagnoses and running so many tests that they end up treating a patient for something better left alone, he said. “You have to find the right balance.” he said.

Few researchers have examined outpatient misdiagnosis before, said Gordon Schiff, a general internist and associate director of the Center for Patient Safety Research and Practice at Brigham and Women’s Hospital and an associate professor at Harvard Medical School.

“The problem of diagnostic errors in general has not been front-and-center in the patient safety movement until recently. And the problem of outpatient safety and diagnostic safety in the outpatient setting has been even more overlooked and harder to get our hands around,” he said. “This [new study] is a very good first pass at trying to really in a more rigorous way establish the incidence of diagnostic errors.”

A definition of diagnostic error hasn’t even been established, said Schiff, whose own definition differs slightly from Singh’s.


In their paper, Singh and his colleagues analyzed data from three previous studies -- two about cancer and one looking more generally at primary care diagnostic errors -- that all shared similar definitions of outpatient misdiagnosis. By looking at all three, they were able to present a fuller picture of the problem, and come up with an overall figure of 5 percent misdiagnosed, Singh said.

Because misdiagnosis is a multifaceted problem, it will require a multifaceted solution, Singh said.

Patients need to be proactive about their care, telling their doctor about any medications they may be taking or problems they are having, and asking questions when they don’t understand, or don’t get a response, said Dr. Lewis Levy, vice president of Corporate Medical Quality at Best Doctors, a Boston-based second opinion service offered by companies as a medical benefit.

“One shouldn’t be walking out of the office pondering,” said Levy, also an internist at Harvard Vanguard Medical Associates in Kenmore Square. “Don’t be shy. Be curious.”

Patients should also ensure that all specialists have access to their medical data, and ask for a second opinion when they’re uncomfortable or unsure about the first -- a good doctor won’t mind, Levy said.

The doctors themselves should ask colleagues for a second opinion when they’re unsure of a diagnosis or treatment course, he said.

Systemic changes are needed, too, said Schiff.

“We need to find ways of supporting physicians,” he said. “To hard-wire some of the diagnostic safety nets, like making sure follow-up happens.”


There also needs to be a way for doctors to hear about their errors, so they can learn from them, Schiff said. “There’s a lot of learning that should be going on, that’s not.”

Karen Weintraub can be reached at weintraubkaren@gmail.com.