Clinical Reasoning in EM

by Todd Guth, MD

Edited by Tom Morrissey


What is Clinical Reasoning?

Clinical reasoning is a set of problem solving skills used by physicians to generate a meaningful differential diagnosis based upon a patient’s presenting features. Perhaps more importantly, it is also involves continually refining this differential by the development of diagnostic possibilities through additional testing. This process leads to the creation of an appropriate treatment strategy for the patient.  Jerome Kassirer, former editor of the New England Journal of Medicine, describes clinical reasoning (also known as clinical cognition) as the “range of strategies that clinicians use to generate, test, and verify diagnoses, to assess the benefits and risks of tests and treatments, and to judge the prognostic significance of the outcomes of these cognitive achievement.”  Kevin Eva, a prominent medical educator, describes clinical reasoning as “the ability to sort through a cluster of features presented by a patient and accurately assign a diagnostic label, with the development of an appropriate treatment strategy as the end goal.”   The most distilled definition of clinical reasoning is “How to think like a doctor.”

Clinical reasoning is also referred to as clinical decision-making and medical problem-solving.  Ultimately, it is the process of how physicians make clinical decisions.  Meta-cognition, a term found in the clinical reasoning literature, is the process of “thinking about” the way in which clinicians “think.” Starting to develop clinical reasoning early in medical training allows for basic principles of problem-solving and decision-making to be introduced along side of the development of clinical skills such as history taking and physical examination.

 The Concept of Problem Representation

One of the most important and powerful skills that you can acquire as a physician is the ability to glean an accurate and concise medical history from a patient.  This not only develops rapport with patients and identifies their agenda for seeking medical attention, but it also provides you with the historical evidence you will need to frame your thinking about what diagnoses may be causing the patient’s symptoms.

During the time you are gathering historical information, you should also be beginning to formulate what you think all this information means: What is the patient really trying to tell me? This conceptualization is extremely important, as it will profoundly color how you present the “subjective” part of your case presentation or ED note

This concept is known as problem representation in the clinical reasoning literature.   The problem representation not only involves historical information, but usually includes components of the physical examination.  The problem representation is different than the patient’s story in that it is not merely a reorganization of the patient’s history and physical, but it is a selective interpretation of the patient’s story.  The information you gathered is not just listed or “data dumped,” but instead organized, prioritized, filtered and interpreted in a way that you chose in order to lead your readers or listeners to your differential diagnosis.  You, as the storyteller, get to select, organize, and frame the patient’s story and physical exam in a way that helps drive listeners (or readers) toward a prioritized differential diagnosis and appropriate diagnostic and treatment plan.  The problem representation frames the way that you, as the clinician, understand and think about the patient’s subjective story and objective examination and labs.  In other words, the problem representation should contain those key features of the history and physical examination that drive your working differential diagnosis and that ultimately lead to a final diagnosis.  Figure 1 places some imagery to a few important concepts in clinical reasoning.


Imagery for Two Fundamental Concepts in Clinical Reasoning
Imagery for Two Fundamental Concepts in Clinical Reasoning
Imagery for Two Fundamental Concepts in Clinical Reasoning
Imagery for Two Fundamental Concepts in Clinical Reasoning

The Concept of Key Features

Key features can be thought of as all those historical and physical examination attributes that help a physician prioritize their differential diagnosis and distinguish one potential diagnosis from another.  Within every patient’s story and their physical examination, there will be discriminating pieces of both subjective and objective information that allows you to determine what may be going on with the patient. These are the key features. In the strictest sense, key features help a physician rank one diagnosis more likely than another.  Only by having a good understanding of the pathophysiology, the signs and the symptoms for the illnesses on your differential diagnosis, and a decent amount of clinical experience (which will come with time),  can you use the key features of the patient’s problem representation to assess for “goodness of fit” and to distinguish among the various entities in the differential diagnosis.  (See Figure 2)  In the mind of the diagnostician, the best key features have the most discriminating power for selecting the most probable diagnosis. This powerful part of your assessment needs to be included in both your written and oral communications with other medical providers.


Figure 2: Assessing for Goodness of Fit is Determined by the Key Features
Figure 2: Assessing for Goodness of Fit is Determined by the Key Features


As your experience with various illness increases and your understanding of patho-physiology improves, you will better understand which aspects of the patient’s presentation represent the key features.   It’s all about pattern recognition, and you have to look at a lot of patterns to get good at it. While you may not know all the particular key features of patient’s presentation right now, its important to introduce these concepts early in your medical training.   This will only improve with continued diligence with your studies and attention to details in your clinical skills acquisition: focused repetition.

The Concept of Illness Scripts

Just as a patient seeking medical attention has a story to tell, illnesses have their own stories that they can tell.  The stories that illnesses tell are known as illness scripts.  An illness script is the way we expect a patient with a particular disease to look, act or behave.  It includes the patient’s presenting symptoms and complaints, demographic features, overall appearance, physical exam, and initial diagnostic test results.   As an example, the classic illness script for acute appendicitis is a young male patient presenting with right lower quadrant pain and tenderness, fever, anorexia, vomiting, and guarding on exam.

In promoting clinical reasoning, physicians compare the patient’s problem representation to various illnesses in the differential diagnosis.  The more closely an illness script matches the patient’s problem representation, the more likely it is to be the correct diagnosis.  One method by which clinicians “think like a doctor” is to compare the various illness scripts in the differential diagnosis to the patient’s problem representation (see figure 3).  Making sophisticated judgment calls about the goodness of fit between the problem representation and various illness scripts is one way that clinician’s make decisions about what is going on with their patients. This is known as intuitive clinical reasoning.

Figure 3. Clinical Reasoning in Action
Figure 3. Clinical Reasoning in Action

We recognize that atypical presentations of common illnesses (and unusual illness) can and do occur. Clinicians commonly do not have a perfect match for the patient’s problem representation.  In uncertain cases additional history, physical  examination, or other testing is used to evaluate your hypothesis as to what is the true underlying diagnosis.  As you gain experience with the myriad of scripts with which disease can present, your understanding of these illness, as well as the variations and subtleties of illness scripts, will become rich and nuanced.

Infusing H&P Notes with Clinical Reasoning

Explain your reasoning in your documentation. To infuse your H&P notes with clinical reasoning, highlight these clinical reasoning concepts in the assessment portion of the H&P note.  Although the best H&P note writers will infuse clinical reasoning throughout their H&P notes, the assessment portion of the note is the most obvious and easily developed portion of the H&P note for displaying clinical reasoning. (Its also where readers will look when they are in a hurry). This is done through the creation of a summary statement that captures the patient’s problem representation, the development of a problem list with prioritized differential diagnoses, and the comparing and contrasting of the differential diagnosis for each problem.  These steps are each discussed below.

Summary Statement and Problem List

Every assessment should begin with a summary statement.  The summary statement is a written sentence or two that captures the patient’s problem representation and highlights the most relevant key features.  Traditionally, the summary statement would contain the patient’s demographic information (such as age and gender), and those pieces of information from the history and physical that drive your prioritized differential diagnosis.  Leave out information about ethnicity or race unless its useful as a key feature from the patient’s problem representation.   In these two sentences you should highlight those key features of the patient’s problem representation that foretell what you think is going on with the patient, and lead to your prioritized differential diagnosis.

Developing a Prioritized Differential Diagnosis

Most physicians have a method for developing a differential diagnosis even though they may not be able to explain how it is that they do. They may be doing it unconsciously.  As young diagnosticians, you will likely need some guidance in coming up with a solid working differential diagnosis.  Different medical specialties often expect different things in their working differential diagnoses. Some specialties prefer a concise differential diagnosis (i.e. surgery or emergency medicine) while others prefer a through or very complete differential diagnosis (i.e. internal medicine or pediatrics). A number of analytical tools that serve a mnemonics have been suggested to help junior learners with developing a differential diagnosis (VINDICATE, VITAMIN C, SPIT) where each letter reminds us of a category from which a possible diagnosis might be considered.  In emergency medicine, a prioritized differential diagnosis commonly includes the most likely or probable diagnosis listed first, then serious or can’t miss diagnoses, followed by less likely and interesting or treatable diagnoses.  (See Below).

Prioritized Differential Diagnosis

  1. Tier 1 : The Most Likely or Probable Diagnosis
  2. Tier 2 : Serious or Can’t Miss Diagnoses
  3. Tier 3 : Less Likely or Less Probably Diagnoses
  4. Tier 4 : Interesting or Treatable Diagnoses Objective

Seek to match the patient’s problem representation to the various illness scripts that you are considering in your prioritized differential diagnosis.  The development of sophisticated judgment about the goodness of fit between the problem representation and various illness scripts is difficult, but this prioritized differential diagnosis framework should help you develop a solid differential diagnosis for the assessment section of your note.

Comparing and Contrasting your Differential Diagnosis

The final skill to develop in the assessment portion of the H&P note is the comparing and contrasting of your differential diagnosis.  To do this properly you must highlight the various key features you identified as part of the patient’s problem representation. You should explain why you think that one diagnosis ranks over another in your differential, or why you want to do more testing to rule out certain serious illnesses.  Demonstration of a comparison and contrast of the various illness scripts in your differential diagnosis shows a sophisticated level of clinical reasoning in the eyes of your evaluators and peers. Anyone reading your notes, or hearing your oral presentations, will fully understand your thought processes.  The more clinical reasoning that you demonstrate in your notes and communications, the better you will perform in your rotations, and ultimately, the better that you will care for your patients. Figure 5 summarizes the key steps to demonstrate your clinical reasoning skills in the assessment portion of the H&P note.

Figure 5: Clinical Reasoning Concepts the Assessment Section of a H&P Note

Clinical Reasoning in Assessment Section of the H&P note

  • Highlights the patient’s Problem Representation and Key Features in the Summary Statement
  • Develops a Prioritized Differential Diagnosis of Most Likely and Serious Conditions
  • Compares and Contrasts the various Illness Scripts in the Prioritized Differential Diagnosis using Key Features



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