While it’s important not to think immediately of zebras when hearing hoofbeats, it’s just as important not to assume it’s always a horse. The delicate balance between not jumping to the seemingly obvious diagnosis without overanalyzing and overtesting is familiar to all physicians, and
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“When these errors are made, it’s not because physicians lack knowledge, but they go down a wrong path in their thinking process,” Richard Scarfone, MD, a pediatric emergency medicine physician at the Children’s Hospital of Philadelphia, told attendees at the annual meeting of the American Academy of Pediatrics, held virtually this year. “An important point to be made here is that how physicians think seems to be much more important than what physicians know.”
Dr. Scarfone and Joshua Nagler, MD, MHPEd, director, pediatric emergency medicine fellowship program at Children’s Hospital Boston, presented a session on the cognitive biases that can trip up clinicians when making diagnoses and how to avoid them. Research shows that the rate of diagnostic error is approximately 15%. Although those findings come from studies in adults, the rates are likely similar in pediatrics, Dr. Scarfone said.
A wide range of clinical factors contribute to diagnostic errors: limited information, vague or undifferentiated symptoms, incomplete history, multiple transitions of care, diagnostic uncertainty, daily decision density, and reliance on pattern recognition, among others. Personal contributing factors can play a role as well, such as atypical work hours, fatigue, one’s emotional or affective state, a high cognitive load, and others. On top of all that, medical decision-making can be really complex on its own, Dr. Scarfone said. He compared differential diagnosis with a tree where a single leaf is the correct diagnosis.
System 1 thinking: Pros and cons
Dr. Scarfone and Dr. Nagler explained system 1 and system 2 thinking, two different ways of thinking that can influence decision-making that Daniel Kahneman explained in his book “Thinking, Fast and Slow.” System 1 refers to the snap judgments that rely on heuristics while system 2 refers to a more analytic, slower process.
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Neither system 1 nor 2 is inherently “right or wrong,” Dr. Scarfone said. “The diagnostic sweet spot is to try to apply the correct system to the correct patient.”
Heuristics are the mental shortcuts people use to make decisions based on past experience. They exist because they’re useful, enabling people to focus only on what they need to accomplish everyday tasks, such as driving or brushing teeth. But heuristics can also lead to predictable cognitive errors.
“The good news about heuristics and system 1 thinking is that it’s efficient and simple, and we desire that in a busy practice or ED setting, but we should recognize that the trade-off is that it may be at the expense of accuracy,” Dr. Scarfone said.
The advantage to system 1 thinking is easy, simple, rapid, and efficient decision-making that rejects ambiguity. It’s also usually accurate, which rewards the approach, and accuracy increases with time based on memory, experience, and pattern recognition. Doctors develop “illness scripts” that help in identifying diagnoses.
“Illness scripts are common patterns of clinical presentations that usually lead us to a diagnostic possibility,” Dr. Scarfone said. “A classic illness script might be a 4-week-old firstborn male with forceful vomiting, and immediately your mind may go to pyloric stenosis as a likely diagnosis.” But the patient may have a different diagnosis than the initial impression your system 1 thinking leads you to believe.
“Generally, the more experience a clinician has, the more accurate they’ll be in using system 1,” he said. “Seasoned physicians are much more likely to employ system 1 than a newer physician or trainee,” which is why heuristics shouldn’t be thought of as hindrances. Dr. Scarfone quoted Kevin Eva in a 2005 review on clinical reasoning: “Successful heuristics should be embraced rather than overcome.”
A drawback to system 1 thinking, however, is thinking that “what you see is all there is,” which can lead to cognitive errors. Feeling wrong feels the same as feeling right, so you may not realize when you’re off target and therefore neglect to consider alternatives.
“When we learn a little about our patient’s complaint, it’s easier to fit everything into a coherent explanation,” Dr. Scarfone said, but “don’t ask, don’t tell doesn’t work in medicine.”
Another challenge with system 1 thinking is that pattern recognition can be unreliable because it’s dependent on context. For example, consider the difference in assessing a patient’s sore throat in a primary care office versus a resuscitation bay. “Clearly our consideration of what may be going on with the patient and what the diagnosis may be is likely to vary in those two settings,” he said.