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Even Doctors Who Flunked Tests Were Confident About Their Diagnostic Accuracy

Accurate diagnosis is the foundation upon which all treatment rests. A doctor cannot prescribe the right medicine or procedure unless she knows what is wrong with her patient.

That is why the results of a recent study in JAMA Internal Medicine (online, Aug. 26, 2013) are so chilling. Researchers tested over 100 internists on their diagnostic accuracy. The volunteer physicians were presented with four case vignettes. Two were considered relatively easy and two were categorized as difficult. The vignettes were presented online, in four stages. At each stage, the volunteers were asked for possible diagnoses, what additional resources they might need, and how confident they were in their decision.

In this study, 55 percent of the doctors who participated got the correct diagnosis on the two easier cases. Fewer than 6 percent of the internists accurately diagnosed the more difficult cases. The researchers note, “The overall diagnostic accuracy was rather low–31 percent across the 4 cases.”

We think abysmal might be a better adjective. Any high school student who only got 31 percent of the answers correct on a test would flunk. Even though this was a study, lives hang in the balance when doctors miss a diagnosis.

The most shocking aspect of this study had to do with confidence. Despite the fact that over 90 percent of the participants incorrectly diagnosed the difficult cases, they were still surprisingly confident about their diagnostic acumen. Confidence was rated on a scale from 0 to 10, with zero being the lowest and 10 the highest. The average confidence on the easy cases was 7.2. On the more difficult cases, confidence levels averaged 6.4, even though most doctors missed the diagnosis. So confidence was not closely related to accuracy. It was related to whether doctors thought they needed help. The more confident they were, the less likely they were to request (hypothetical) help from consultants or additional tests. The authors conclude, “Our study suggests that physicians’ level of confidence may be relatively insensitive to both diagnostic accuracy and case difficulty. This mismatch might prevent physicians from reexamining difficult cases where their diagnosis may be incorrect.”

Many readers of this column have shared stories about misdiagnoses. This one is particularly tragic: “My father died as a result of a missed diagnosis. He was in the coronary intensive care unit at a teaching hospital after suffering a heart attack. He was treated first at a community hospital, then transferred to the teaching hospital for angiography. While waiting for the cardiac surgeon to review the test results, and while on anticoagulants, my father developed knee swelling and pain in the leg used for the angiography. He was treated for days with narcotic painkillers for sciatica, which only made him constipated.

“No one noticed that he was bleeding massively into his abdomen. Lab results demonstrating the blood loss were ignored. Six days after the angiogram, while straining on a bedside commode, he had another cardiac event. Hours later an attending physician finally saw the lab evidence of massive blood loss and ordered blood transfusions. Inexplicably, my father did not get the transfusion until many hours later after his heart muscle was irretrievably damaged. He went into cardiac arrest and died the day before he had been scheduled to go home.

“How do I know all this? Because I am a physician, I requested the chart. The nurses’ notes and lab results told the real story. Most families will never find out about diagnostic errors. They have no way to learn the truth.”

We offer advice on how to avoid diagnostic errors in our book, Top Screwups Doctors Make and How to Avoid Them. There, you will find a list of the diagnoses that are most often missed (pulmonary embolism, drug reaction, lung cancer, colorectal cancer and more on p. 44). You’ll also find, on p. 69, a list of questions you should ask to help reduce the chance of a diagnostic disaster.

If patients take a more active role in the diagnostic process, they may be able to reduce the likelihood of such terrible mistakes.


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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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