Clinician's Corner: Diagnostic errors

Every year, there are millions of medical diagnostic errors that result in a certain number of deaths. Thinking an individual has disease X, when they have disease Y.

One way to minimize these errors was popularized in the book Thinking Fast and Slow, by Daniel Kahneman, which discusses System 1 and System 2 thinking.

System 1 thinking is fast. It’s what people call a “snap decision.” For example, if asked what 1 + 1 is, most people automatically blurt out “2” without consciously thinking about it.

System 2 thinking, on the other hand, is slow. It’s analytical and takes more conscious effort.

If asked what 17 x 24 was, most people need a bit of time to get to the answer which is 408. We fluidly switch back-and-forth from System 1 to System 2, and while they’re not two physically separate systems in the brain, they do represent a model that can help us to better understand the different ways that the brain operates.

When it comes to making a diagnosis, System 1 instantly kicks in when we recognize a pattern in a clinical presentation.

For example, let’s say a 35-year-old man with major depressive disorder, hypertension, and diabetes comes to a busy primary care clinic with worsening feelings of anxiety, rapid breathing, and occasional right-sided chest pain over the past 30 minutes.

He says, “It feels like the world is closing in on me.” Some clinicians would make a fast, System 1 diagnosis that the patient is having a panic attack.

With that diagnosis in mind, they might do a quick physical exam, give the man some anti-anxiety medications, and send him home.

But if System 2 thinking had been deliberately used, the clinician might’ve recognized that there’s one aspect of this story stands out – it’s the right-sided chest pain.

Rather than a panic attack, this man may actually be having an atypical presentation of a heart attack. There are several types of cognitive mistakes that can lead to diagnostic errors.

The first is called premature closure. It’s when the initial diagnosis is heavily focused on, and the mind becomes closed to other possibilities.

Another cognitive mistake is representative bias, and that’s when a clinician is looking for the classic presentation of the disease and the patient presents with an atypical or variant pattern.

Experienced clinicians know variants of common diagnoses are frequent, and they happen more often than we immediately think.

Generally speaking, System 1 thinking becomes more accurate as clinicians move through their careers and can recognize atypical or variant presentations.

For example, a junior primary care physician, may have a deep understanding of panic attacks, but may not be able to distinguish them from atypical MI’s.

A more experienced clinician might have seen that very scenario during their career and immediately recognize it. Alright, as a quick recap… While System 1 thinking is fast and often correct, it needs to self-monitored.

It can make snap errors as quickly as correct diagnoses. System 2 thinking is slow and analytical, and can help to avoid mistakes made by System 1.