1/ Clinical Reasoning Series – Cognitive Bias

Ever felt the thrill of making crucial diagnosis? The pain of missing a diagnosis? Yeah, us too

Clinical reasoning is hard, so let’s talk about it. Our 1st post in a new series starts today. Let’s talk about Biases.

#MedTwitter

2/ Basic Definitions:

>Heuristic: a cognitive shortcut based on prior experience & pattern recognition

>Cognitive Bias: when a heuristic leads to misdiagnosis or inappropriate treatment

We need heuristics b/c reasoning every decision from 1st principles would take forever!

3/ Heuristic vs Bias

There is a fine line b/t a heuristic and a bias

For example: 80yoM w/ CAD p/w SOB, ankle edema, and alveolar filling on CXR. You start abx PNA
If he improves, PNA was a good call
If he gets worse because he has failure, PNA was “premature closure”

4/ Cognitive Biases

Heuristics are based on knowledge and prior experience. The more you practice and learn, the better you become at using them. Biases happen when heuristics go wrong.

Check out this comparative list of heuristics and biases.

Chart by @CaseyMcQuadeMD

5/ Errors of Prevalence and Errors of Ego

Most biases fit into 1 of these 2 categorie:
You forgot the base rate of a disease - base rate neglect, representativeness restraint, availability bias
You want to be right (and don't we all?) - confirmation bias, premature closure

4/ Check for Understanding (give this case a try!)

40yoF w/ obesity p/w RUQ pain, anorexia
VS normal
RUQ pain. Murphy’s sign negative. No icterus
WBC 14, AST 300, ALT 400, HAV/HBV/HCV neg
RUQ US: dilated CBD, no stones
>ANA = 1:320

Q1: Which diagnosis is most likely?

5/ Answer #1

A passed gallstone is most likely based on the prevalence of gallstones, CBD dilation, & elevated LFTs (commonly caused by gallstones/cholangitis)

Your MS3 saw autoimmune hepatitis last month and thinks AIH is most likely here.

Q2: What biases are likely at work?

6/ Answer #2

All are possibly correct (I can’t read your student’s mind...):

Gallstones are common, AIH is rare
They just saw AIH recently (availability)
They focus on the ANA (nonspecific) but disregard the dilated CBD
“No gallstones” is not “classic” of gallstone dz

7/ Next Steps

So how do you combat bias?
Turns out it’s very hard:

Things that may decrease bias:
-Doing an ”effortful pause” to check yourself for bias
-Using diagnostic frameworks (e.g @CPSolvers)
-Using lists

Remembering to do these is hard even with practice!

8/ Further Reading

Thanks for reading!

We’re going to keep this series going in the future. If you’re interested in reading more, check out these:

“Thinking, Fast and Slow” by Daniel Kahneman
“Sources of Power” by Gary Klein
https://pubmed.ncbi.nlm.nih.gov/32311734/ 
https://qualitysafety.bmj.com/content/26/2/87