At least one in 20 adults is misdiagnosed in outpatients clinics in the United States every year, according to a recent study HealthDay reported.

New research suggests that the misdiagnoses of nearly 12 million people nationwide poses a "substantial patient safety risk and that there should be renewed efforts to monitor and curb the number of misdiagnoses, HealthDay reported.

"We've had this problem for a while," Hardeep Singh, one of the researchers involved in the study, told Vox.com. "We just haven't been able to measure it."

For the study, researchers combined and analyzed data from several published studies, involving hundreds of medical records, samples from a large pool of outpatient clinic visits.   They reviewed the records in detail to see if a diagnostic error has been made. 

Based on their findings, about 5.08 percent of American patients are misdiagnosed in outpatient settings every year, suggesting that at least 1 in 20 US adults is misdiagnosed every year.

And around half of these mistakes could potentially be harmful, if previous research is anything to go by, researchers said. For example, if doctors diagnose a cough brought on by lung cancer as a cough brought on by a cold, the cancer "is going to have time to spread and, therefore, become more difficult to treat," Vox.com reported.

"To date, patient safety improvements have largely focused on hospital stays and issues such as infections, falls, medication errors," researchers said in a press release. "But most diagnoses are made in outpatient clinics where patients are looked after by several different healthcare teams and few safety concerns are ever reported."

Singh said the purpose of the study was to "to start a conversation with stronger methodology that might invite further research into the issue."

Researchers said Healthcare organizations, patient advocates, policymakers, and researchers should use the findings to push for further strategies to improve patient safety in this area.