The Big Miss: Cognitive Bias and the Problem of Misdiagnosis

Mark Perdue PA-CBedside Diagnostic Challenge, Emergency Medicine, Family Medicine, Internal Medicine, Medical News, Nurse Practitioner, Nursing RN/PN, Pediatric Emergency Medicine, Pediatric Medicine, Personal Education, Physician Assistant

cognitive bias and misdiagnosis

Cognitive Bias and the Problem of Misdiagnosis: Avoiding The Big Miss

The problem of cognitive bias and its important role in misdiagnosis is well documented. The phenomenon of cognitive bias can take several forms and affects the capacity of both new clinicians and seasoned professionals. A consensus is emerging that clinicians need to be aware of cognitive biases and practice educational and clinical strategies to reduce the effects of cognitive bias on our ability to effectively diagnose.

Cognitive Deficits vs. Cognitive Biases

It may be helpful for us to parse out two kinds of vulnerability to error in clinical reasoning cognitive deficits and cognitive biases.

Cognitive deficits transiently impair a clinician’s capacity to correctly reason. Some examples of transient deficits include fatigue, extreme stress, or illness. All of these transient states have been shown to impair a clinician’s performance and in normal circumstances may be prevented or managed. Other cognitive deficits may include training gaps lacunae in knowledge base and skill set that impair a clinician’s ability to correctly diagnose and treat illness. These gaps in knowledge also may be anticipated, prevented and managed by clinicians actively seeking out additional training to close these gaps.

The second type of vulnerability to medical error, cognitive bias, is inextricably bound up with our normal capacity to function. A clinician may be well-rested, calm and extremely well trained but still be subject to the vulnerability of cognitive bias.

Cognitive bias has been defined generally as a tendency to reach inaccurate conclusions about a particular state of affairs despite having full access to the facts. We look but we do not see. This tendency to make misjudgments about the world around us is hardwired in the way our brain works. Our minds are constantly sifting through enormous amounts of information which we interpret through a series of mental shortcuts called heuristics.

Heuristics are ways of thinking that allow us to make sense of our world and without heuristics our reality would be a jumbled mess. These mental shortcuts allow us to efficiently interpret and move through the world and serve us well in the overwhelming majority of situations. However, in atypical or unusual presentations, heuristics tend to focus our minds on the wrong data.

cognitive bias types 20 cognitive biasescognitive bias codex

Cognitive Bias and Misdiagnosis Examples

Consider the following misdiagnosis scenarios:

Case 1:

A 69-year-old diabetic female presents to the emergency department complaining of jaw pain and nausea. The patient is triaged with a chief complaint of “toothache,” given an emergency severity Index rating of four (low - only needing a prescription) and put at the bottom of the pile. She waits 3 hours to be seen at which time she is found to have experienced a myocardial infarction.

Case 2:

A 12-year-old male presents to the emergency department with nausea, vomiting, diarrhea, and generalized weakness. He is discharged from the emergency room and returns in 24 hours dying of sepsis.

In each of these scenarios patients presented to facilities with properly trained clinicians and yet all of them suffer the fatal consequences of misdiagnosis. What happens when clinicians miss life-threatening diagnoses? 

Our initial response is typically one of blame. We are inclined to believe that the clinicians had a lapse of judgment, loss of focus, or maybe had gaps in their training or knowledge base. Research on the subject of errors in clinical reasoning suggest that misdiagnosis is more likely to be caused by mental errors called cognitive biases.

Cognitive Bias Examples Explained

Cognitive bias case #1

In the first case noted above 65-year-old female with “toothache” that turned out to be a myocardial infarction may be thought of as a case of framing. Framing bias is a type of bias that occurs when circumstances surrounding a presentation skew our thinking away from the most important facts. The majority of patients with jaw pain may very well have a “toothache,” and so it’s not unreasonable for a triage nurse to think of that patient’s complaint as dental in nature.

However, emergency medicine clinicians know that diabetic females are prone to atypical presentations of acute coronary syndromes. Throw in some nausea and we begin to get a sense that this patient was at increased risk for an atypical presentation of a heart attack. Once the patient has been described in a certain way other people tend to pick up on those descriptions and repeat them in their minds.

Cognitive bias case #2

The second case mentioned above the 12-year-old with nausea, vomiting, diarrhea, and generalized weakness was likely a case of availability bias. The 12-year-old’s complaints are frequently seen in cases of gastroenteritis, a usually harmless and self-limiting viral illness. If a clinician sees five patients with gastroenteritis the sixth patient that presents with those same symptoms will seem strikingly similar to the previous five patients. “I’ve seen this five times today. There must be something going around.”

Our minds become primed with recent, available cases and we tend to focus on the similarities between the available cases.  Our histories and physicals become skewed by our presumptions and we tend to overlook clinical findings that would work against our presumptive diagnosis. Unfortunately, the sixth patient that presented with nausea, vomiting, and diarrhea was our 12-year-old who ended up having sepsis, not gastroenteritis, and died of septic shock.

how cognitive bias contributes to misdiagnosis

How to Recognize Cognitive Bias and "Debias" Your Clinical Decisions

While it is not possible to eliminate the impact of cognitive errors – they are mostly unconscious and thus we are unaware of their impact – it is possible, and highly recommended, to consider both their existence and their effects when interacting with patients and making clinical decisions. Unfortunately, the medical profession has tended to avoid discussion of cognitive errors, and when the topic is addressed, it is frequently met with pessimism. This makes it difficult to bring errors in thinking out into the open so that they are routinely discussed and considered in medical practice, in medical school, and as part of continuing education events.

To decrease the incidence of clinical errors in judgment, it is critical for physicians to learn and practice strategies to mitigate the impact of cognitive biases and heuristics.

These strategies are frequently referred to as “debiasing” techniques.

  • Develop insight and awareness. The greatest danger is when physicians believe that they are immune to errors or biases in their thinking. Invest time in reflection rather than investing time in discounting your humanness.
  • Practice metacognition. It is inherent upon providers to continually assess their thinking processes – in other words, to engage in meta-cognitive practices, which is literally thinking about one’s thinking. Regularly step back from a problem so you can consider your thinking process. Get curious about all aspects of the situation, continually reflecting upon how you are approaching the problem. Ask: How else might I think about this?
  • Consider alternatives. Make a habit of considering other possibilities by frequently asking: What else might this be? Do not be hesitant to consult with colleagues when time permits. Sometimes a fresh set of eyes or ears can detect something that you don’t.
  • Appreciate that uncertainty is a necessary ingredient on the road to rationality. Embrace uncertainty as an opportunity to sharpen your thinking skills and to learn from experience.
  • Accept that errors occur and learn from them. One way that people of all ages learn is through a process of trial and error – using this approach in healthcare decreases the incidence of repeat errors and improves learning skills.
  • Check your ego. Take time to reflect if you are overly invested in being right rather than discovering what you might have missed. Ask: What might I be missing? Reframe errors as opportunities to learn and grow rather than evidence of your competency, worth or status.  Consider these particularly ego-driven biases:
    • The overconfidence bias - the tendency to believe we know more than we do. In medicine, over-confidence is much more likely to be sought and rewarded, causing physicians to avoid showing “weakness” in the face of uncertainty.
    • The confirmation bias - the tendency to attend to information that confirms our beliefs and to discount or neglect information that does not confirm our beliefs.
    • The sunk cost bias - when considerable time, money, and/or energy has been invested, causing people to remain committed to the investment despite evidence that it is not achieving the desired result. This bias is often discussed with financial investments – in medicine, it shows up as sticking with a diagnosis because the physician has invested time, energy, or ego (I don't want to be wrong or be seen as incompetent).
medical error misdiagnosis rates cognitive bias

You Deserve Your Best Chance to Catch Cognitive Bias and Make the Best Diagnosis

Unfortunately, mistakes will sometimes be made, but there will be far fewer if we remain careful for each case.  Blank slate, just the facts, and consider your own humanness - your pace, your stress, your last case "like this" - or your outcomes can suffer.  Stay in control and curious.  Bias is out there!  Make it your habit to take a second look at information and your diagnostic process.  And finally, a firm grounding in practice and ongoing knowledge review can improve your ability to avoid cognitive bias and the perils of one's own diagnostic momentum.


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