A new study shows that at least one in every twenty adults who is treated at an emergency room in a U.S. hospital is given the wrong diagnosis. That means that as many as twelve million Americans are being wrongly diagnosed each year in this country. Experts say that at least half of the six million faulty diagnoses could cause serious injuries or be potentially fatal, according to a patient safety expert who is the first to provide this type of in-depth information about the problems surrounding outpatient situations.

Essentially, people who walk into an emergency room with problems associated with heart failure, pneumonia, blood disorders, and types of cancers could go unrecognized by the attending ER physician. Attempts to quantify these kinds of errors has been difficult to do in the past because most researchers and field experts use different definitions of "mistakes." This has made it hard to track negligence, but these estimates are considered fairly conservative upon interviewing anonymous ER physicians and nurses from throughout the country.

The study includes results from three previous research assignments that were focused on return visits after a visit to a patient's primary care physician, absence of follow-up appointments for abnormalities related to colon and rectal cancers, and repeated cases of lung cancer. The research was conducted by a wide base of field experts from all over the country, thus there were clear definitions of what is considered a mistake consistent throughout the study.

Previous estimates suggested that outpatient and ER misdiagnoses may be close to 5%, but there was never a consistent level of research. Today, most experts agree that this is a fairly accurate estimate and some believe that 5% is actually too low an estimate, especially in areas of high population.  

Source: NBC News, "Misdiagnosed: Docs' mistakes affect 12 million a year" 16 April 2014