A new study reveals that around 12 million people in the US are misdiagnosed in outpatient clinics each year - the equivalent to 1 in every 20 adults. According to the study researchers, the findings pose a "substantial patient safety risk."

The research team, led by Dr. Hardeep Singh of the Veterans Affairs Center for Innovations in Quality, Effectiveness and Safety and the Baylor College of Medicine, both in Houston, TX, says that determining the frequency of diagnostic errors in outpatient clinics is challenging. This is because of varying definitions of error and the fact that data need to be reviewed across an array of multiple health care providers and settings.

In an attempt to reach an estimate, Dr. Singh and colleagues revised the data of three studies that included hundreds of medical records of patients who attended outpatient clinics.

The team then confirmed the number of diagnostic errors over all three studies, which were defined as "missed opportunities to make a timely or correct diagnosis based on available evidence." They note that the criteria for diagnostic errors were comparable across all studies.

In order to estimate the annual frequency of misdiagnoses, the researchers applied the number of overall diagnostic errors to the larger population of all outpatient visits, before applying the figure to the adult population.

Misdiagnoses 'may severely harm 6 million outpatients annually'

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Around 12 million adults in the US are misdiagnosed in outpatient clinics every year - the equivalent to 1 in 20 - according to new research.

Their findings, recently published in BMJ Quality and Safety, revealed that the annual rate of outpatient diagnostic errors stands at 5.08%. This is the equivalent to 12 million adults, or 1 in 20.

The researchers say that although it is unclear as to how many outpatients may be harmed from these misdiagnoses, past research from the team indicated that around 50% of errors "have the potential to lead to severe harm."

This means around 6 million outpatients are at risk of experiencing serious health problems as a result of misdiagnosis.

When asked if these findings are likely to worry individuals who visit outpatient clinics, Dr. Singh told Medical News Today that patients need to be aware of such problems so they can work with doctors to address them.

"This is not a new problem," he added. "These vulnerabilities have always existed but it's only now, through rigorous research in patient safety, that we can measure these problems, define them, identify solutions and improve health care. Patient empowerment and engagement can play a big role here."

Reasons for diagnostic errors 'need to be addressed'

Dr. Singh said there are many reasons why so many outpatients are misdiagnosed. For example, he said that outpatient environments are busy and this can put physicians into time-pressured conditions that may lead to uncertainty in patients' symptoms.

Furthermore, he said that many system or organizational factors can play a part in misdiagnoses. We recently reported on a study revealing that, as a result of the increasing number of laboratory tests available to doctors, they face uncertainty when ordering and interpreting them, which may impact patient diagnosis.

In order to improve the accuracy of diagnoses for outpatients, Dr. Singh said that these problems need to be addressed:

"We need to understand the contributory factors and we need to study and implement preventive strategies.

Patient empowerment is key but so is better cognitive support to physicians, use of effective information technology to help them make better decisions, better follow-up and tracking of patients and their abnormal findings and better policies both at local and national levels to address this problem."

Dr. Singh said the research team is now working on developing technology-based strategies to improve follow-up and tracking of abnormal findings in health care settings with the help of electronic medical records.