The Startling Truth About Doctors and Diagnostic Errors

By Maggie Mahar and Niko Karvounis, Health Beat. Posted June 19, 2008.

This article originally appeared on Health Beat.

Despite all of the talk about medical errors and patient safety, almost no one likes to talk about diagnostic errors. Yet doctors misdiagnose patients more often than we would like to think. Sometimes they diagnose patients with illnesses they don't have. Other times, the true condition is missed. All in all, diagnostic errors account for 17 percent of adverse events in hospitals, according to the Harvard Medical Practice Study, a landmark study that looks at medical errors.

Traditionally, these errors have not received much attention from researchers or the public. This is understandable. Thinking about missed diagnosis and wrong diagnosis makes everyone -- patients as well as doctors -- queasy. Especially because there is no obvious solution. But this past weekend the American Medical Informatics Association (AMIA) made a brave effort to spotlight the problem, holding its first-ever "Diagnostic Error in Medicine" conference.

Hats off to Bob Wachter, associate chairman of the Department of Medicine at the University of California, San Francisco, and the keynote speaker at the conference. Wachter shared some thoughts on diagnostic errors through his blog Wachter's World.

Wachter begins by pointing out that a misdiagnosis lacks the concentrated shock value that is needed to grab the public imagination. Diagnostic mistakes "often have complex causal pathways, take time to play out, and may not kill for hours [i.e., if a doctor misses myocardial infarction in a patient], days (missed meningitis) or even years (missed cancers)." In short, to understand diagnostic errors, you need to pay attention for a longer period of time -- not something that's easy to do in today's sound-bite driven culture.

Diagnostic errors just aren't media-friendly. When someone is prescribed the wrong medication and they die, the sequence of events is usually rapid enough that the story can be told soon after the tragedy occurs. But the consequences of a mistaken diagnosis are too diffuse to make a nice, punchy story. As Wachter puts it: "They don't pack the same visceral wallop as wrong-site surgery."

Finally, Wachter observes, it's hard to measure diagnostic errors. It's easy to get an audience's attention by telling it that "the average hospitalized patient experiences one medication error a day" or that "the average ICU patient has 1.7 errors per day in their care."

But we don't have equally clean numbers on missed diagnoses. As a result, he points out, "it's difficult to convince policy makers and hospital executives, who are now obsessing about lowering the rates of hospital-acquired infections and falls" to focus on a problem that is much more difficult to tabulate.

This is a recurring problem in programs that strive to improve the quality of care: We are mesmerized by the idea of "measuring" everything. Yet, too often, what is most important cannot be easily measured. Wacther recognizes the urgency of the problem: "As quality and safety movements gallop along, the need to" address diagnostic errors" grows more pressing," he writes. "Until we do, we will face a fundamental problem: A hospital can be seen as a high-quality organization -- receiving awards for being a stellar performer and oodles of cash from P4P programs -- if all of its 'pneumonia' patients receive the correct antibiotics, all its 'CHF' patients are prescribed ACE inhibitors, and all its 'MI' patients get aspirin and beta blockers.

"Even if every one of the diagnoses was wrong."

Why so many errors?

Medicine is shot through with uncertainty; diseases do not always present neatly, in textbook fashion, and every human body is unique. These are just a few reasons why diagnosis is, perhaps, the most difficult part of medicine.

But misdiagnosis almost always can be traced to cognitive errors in how doctors think. When diagnosis is based on simple observation in specialties like radiology and pathology, which rely heavily on visual interpretation, error rates probably range from 2 percent to 5 percent, according to Drs. Eta S. Berner and Mark L. Graber, writing in the May issue of the American Journal of Medicine.

By contrast, in clinical specialties that rely on "data gathering and synthesis" rather than observation, error rates tend to run as high as 15 percent. After reviewing "an extensive and ever-growing literature" on misdiagnosis, Berner and Graber conclude that "diagnostic errors exist at nontrivial and sometimes alarming rates. These studies span every specialty and virtually every dimension of both inpatient and outpatient care."

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Maggie Mahar is a fellow at the Century Foundation and the author of Money-Driven Medicine: The Real Reason Health Care Costs So Much (Harper/Collins 2006).

Niko Karvounis is a program officer with the Century Foundation in New York City, where he works on issues of socioeconomic inequality and healthcare. He is a regular contributor to Health Beat, the foundation’s healthcare blog.

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