Clinical Reasoning and Differential Diagnosis

Introduction

• Presenter: Eric Strong from Stanford University and Palo Alto VA Hospital
• Series Title: A Guide to Clinical Reasoning
• Objectives:
  • Standardized approach to generating a differential diagnosis.
  • Create concise problem representations using semantic qualifiers and clinical syndromes.
  • Understand frameworks for key features of a presentation.
  • Know categories of diagnoses to include in the differential.

Importance of Clinical Reasoning

• Clinical reasoning is often misunderstood due to dense terminology.
• Focus will be practical, minimizing unfamiliar terms.
• Clinical reasoning is a collection of related skills, not a single skill.
  • Involves interpreting subjective and objective data, evaluating data accuracy, synthesizing data, evaluating literature relevance, applying biostatistics, and integrating knowledge for decision-making.

Steps to Generating a Differential Diagnosis

Step 1: Acquire Data

• Use all available sources: patient interview, examination, tests, chart review, and collateral information.
• Avoid anchoring bias: the tendency to focus too much on early information and not update based on new data.

Step 2: Identify Key Features

• Key features help differentiate between diagnoses.
• Example: Episodic chest pain triggered by exercise indicates cardiac ischemia.

Step 3: Create Problem Representation

• Use semantic qualifiers and synthesize into clinical syndromes.
• Problem Representation: Concise summary of relevant aspects using medical terminology.
• Semantic Qualifiers: Qualitative abstractions of symptoms.
• Clinical Syndromes: Group related findings into a single term.

Step 4: Adopt a Framework

• Frameworks help categorize differential diagnoses and may be anatomical, physiological, etc.
• Example Frameworks:
  • Acute renal failure: Pre-renal, Intra-renal, Post-renal.
  • Anemia: Hypoproliferative, Hyperproliferative.

Step 5: Apply Key Features to the Framework

• Use key features to estimate likelihood of diseases or pathophysiologic states.
• Expertise in clinical reasoning involves differential impact of key features on framework components.

Understanding Differential Diagnosis

• Definition: List of possible diagnoses explaining a patient's presentation, prioritized by likelihood and danger.
• Should include the most likely diagnosis, common diagnoses, and rapidly fatal ones.
• Avoid overly broad differentials; aim for 4-6 diagnoses in internal medicine.

Tips and Cautions

• Framework is different from a differential diagnosis.
• Atypical presentations of common diseases are often more likely than typical presentations of rare diseases.
• Textbook descriptions may not always reflect true typical disease presentations.

Conclusion

• Covered five steps to a differential diagnosis.
• Further examples to be discussed in parts 2 and 3 of the series.