Clinical Reasoning (1st draft)

Clinical Reasoning Algorithm
The goal here is to start teaching clinical reasoning on day 1 of medical school. Though the students don’t yet have the medical knowledge to apply, I bet they can learn the process.

01: An Overview

The first video gives an overview of the process. There is a lot in here that will be unpacked in subsequent videos: how to make a differential diagnosis, how to select which questions to ask, Bayesian analysis (though not called out by name — too scary), System I and II thinking.

An Example

This video goes through an example case. The details are watered down, but even then may be too complex. I’m hoping that the students don’t get too hung up on the specifics but focus on the cycle of gathering data → testing hypotheses.

Watching a video should be followed by an application piece, so I thought students could step through a worksheet together in small groups. Most people can think of a few diagnoses that cause shortness of breath. I think.


02: Data Gathering

This first video looks at an overview of Data Gathering. Data can be gathered from several different sources, but we’ve boiled it down to these areas:

  1. Initial data
  2. History
  3. Physical Exam
  4. Testing

From each of these different sources, you’ll gather data. Some data you gather on everyone. Some data you only gather when you’re suspecting a particular diagnosis.

You’ll also need to organize the data using problem lists, semantic qualifiers (using one from a pair of opposite adjectives) and ultimately making a summary statement.

An example

Just let me know if this case presentation using the framework is helpful. I can change it if needbe.

Illness Scripts

Illness scripts are the descriptions of a disease and contain several components:

  • Pathophysiology – what causes a disease?
  • Epidemiology – who gets the disease?
  • Timing – when it starts, when it stops, and what happens in between?
  • Symptoms and signs – What might you find on history and physical exam?
  • Diagnostics – what testing would you need to help rul-in or rule-out this disease?
  • Treatment – how would you treat the disease once ruled-in?

03: Making and Testing Hypotheses (the differential diagnosis)

in this video, we talk about the different ways that you can construct a differential diagnosis.

  • Pattern-recognition: looks like something you saw before (of course you need to have seen things before for this to work)
  • Most probable: what do most people who look like this have?
  • Must-not-miss: what would be dangerous, potentially lethal, to miss?
  • Systematic approaches: Anatomic: what organs are in this part of the body and what can go wrong with them?
  • Systematic approaches: Physioologic: how does this disease process work and what could explain it? 
  • Mnemonics: use memory aides to think of long lists of seeming unrelated diagnoses (they’re probably not unrelated given they’re on the same list, right?)

The first one is a fast, automatic method. This sort of thing comes with experience and is called System I thinking (if you read Malcom Gladwell’s Blink of Daniel Kahnneman’s Thinking Fast and Slow). This is usually the realm of experience physicians, not rookie medical students. And Captain Kirk.

The remaining methods are somewhat slower and more methodical. These are System II thinking methods. This is what Mr. Spock would do.

Testing Thresholds

This video covers the concept that there is uncertainty in medicine. Though a textbook can make it seem like the definition of a disease is clear and definitive, this is not the case when talking to patients. We like to say “patients don’t like to read the textbook.” Instead we deal with probabilities that cross a threshold.

  • Testing threshold: below this probability, you no longer need to test for a disease. You can rule it out, trash it.
  • Treatment threshold: above this probability, you no longer need to test for a disease. You can rule it in, start treating it.

Anything that falls in between those two thresholds is still in play. We need to gather more information.

Where you set those thresholds and the mathematics of how the results of testing pushes the probability up or down will be covered in later videos. This part requires a bit of evidence-based medicine which we’ll get to in time.


This is my first draft in these videos. Please let me know what can make it better for you. Thanks.

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