At least 1 in 20 outpatients misdiagnosed every year, study shows

At least 1 in 20 adults is misdiagnosed in outpatient clinics in the U.S. every year, a new study published in the journal BMJ Quality & Safety indicates. 

The research, which analyzed data from three earlier studies, indicated that the misdiagnosis rate among outpatients - patients who receive treatment without being admitted to a hospital - is approximately 5 percent. When translated to the entire population, the researchers estimate that 1 in 20 adults, or 12 million people nationwide are misdiagnosed every year.

“We called it a misdiagnosis when there was a definite missed opportunity to make a timelier, correct diagnosis based on information available at that time,” Dr. Hardeep Singh, a researcher at the Michael E. DeBakey VA Medical Center in Houston, Texas, told “We would say, ‘Was that opportunity there? Was evidence there? Was it someone who presented with a red flag for colon cancer, who didn’t get a work up?’”

Singh noted that while much progress has been made in patient safety in hospital settings in recent years, few studies have focused on the outpatient experience.

“In some ways, in outpatient [care], it’s challenging; patients move between different systems of care, specialists, radiologists,” said Singh, who is also an associated professor at Baylor College of Medicine Safety. “We had done studies in integrated health care systems and thought it would be good to extrapolate that data to see how commonly these things are occurring, to see what needs to be done about them. And the numbers were quite telling.”

Utilizing data from three of his previous studies, Singh analyzed outpatient misdiagnosis rates from hundreds of medical records. The first study analyzed misdiagnoses in a primary care setting, and the second and third studies analyzed rates of misdiagnosis among lung cancer and colon cancer patients.

In each case, the researchers were characterizing misdiagnoses as times when patients presented clear symptoms that were either missed by a physician or not properly followed up on. Singh emphasized that “red flags” for disease often develop slowly, and the study only considered a patient to be misdiagnosed when clear symptoms were missed by a physician.

“Time often tells you what the diagnosis would be, and that’s natural,” Singh said.

About half of missed diagnoses have the potential to be harmful to a patient’s health, the researchers noted.

“We basically sort of made a prediction based on the cases, as to what the level of harm would be in worst case scenarios for that patient – if it’s just a minor inconvenience, or if a more severe complication, such as a disability, could have happened,” Singh said.

Though Singh’s research did not delve into the causes of the misdiagnoses, he said many factors can affect whether or not a patient receives proper medical care. Previous research indicated that in the outpatient setting, many breakdowns occur during the information-gathering portion of an appointment, when a physician is taking a patient’s medical history and observing symptoms.

With more research, Singh said he hopes systems can be developed to help doctors and patients ensure that proper diagnoses are made in the outpatient setting.

“For instance, right now there is no good way for me to know as a physician the types and times I have misdiagnosed people, because I don’t get any feedback on patients who may have gone to a hospital and gotten another test,” Singh said. “…We need better systems of feeding information back to physicians.”

Singh said patients may also be able to help reduce rates of misdiagnosis by becoming more actively involved in their care – taking the initiative to follow up on medical tests or notifying their doctors quickly if their symptoms continue to worsen.

“Ultimately, we’ll have to acknowledge there’s a lot of uncertainty in diagnosis in primary care settings,” Singh said. “But when there’s uncertainty, that’s the time to tell the patient, ‘I think I’m right, but there’s a good chance I’m not, so please follow up with me in two days if you do not feel better.’ And then the patient feels like, ‘Oh the doctor did tell me he could have been incorrect, I have a fever today, so I’m going to call him now.’”