L 20 Clinical Reasoning and Medical Decision Making — Study Notes
Learning Objectives
- Define clinical reasoning and medical-decision making.
- Describe components of the clinical reasoning process.
- Understand dual-process theory (System 1 and System 2 thinking) and its implications for clinical decision-making.
- Develop the ability to use illness scripts to facilitate clinical reasoning.
- Understand the principles behind creating a differential diagnosis, including the need for comprehensive, organized reasoning to ensure important conditions are not missed.
- List the components of the VINDICATE and SPIT differential diagnosis mnemonic.
- Identify common cognitive biases that can impact clinical decision-making and diagnostic accuracy.
- Develop strategies for recognizing and mitigating biases that can impact medical-decision making.
- Synthesize the principles of clinical reasoning, differential diagnosis, and cognitive bias to make effective, evidence-based clinical decisions.
Clinical Reasoning: Definition and Scope
- The mental process of gathering, analyzing, and synthesizing information to make medical decisions.
- Can be a difficult concept to explain, teach, and replicate.
- Components involve the Clinical Problem or Presenting Patient and what goes on in the provider’s head, leading to the Outcome (Diagnosis and/or Plan).
Timeframe and Variability in Clinical Reasoning
- Can occur in seconds to minutes for a classic presentation of a common problem.
- Can take weeks to months for more complex cases, including literature reviews, consultations with specialists, and seeking opinions of colleagues.
Dynamic Nature and Tenets of Clinical Reasoning
- Dynamic process that involves:
- Clinical knowledge
- Critical thinking
- Pattern recognition
- Tenets of evidence-based medicine
- Goal: Make safe, evidence-based decisions.
Key Questions in Clinical Reasoning (What to Ask/Do)
- What history questions should I ask?
- What physical exam techniques should I perform?
- What labs should I order for this patient?
- What is the most likely diagnosis for this patient?
- What life-threatening diagnoses should I consider?
- Is this patient stable or is this a medical emergency?
- Do I need to refer this patient to a specialist?
Clinical Reasoning: Impact on Practice
- Directly impacts patient outcomes.
- Helps prevent diagnostic errors.
- Core competency of PA practice.
The Clinical Reasoning Process (Five Steps)
- Acquire Data
- Interpret and Organize Data
- Make hypotheses
- Test Hypotheses
- Diagnosis and Plan
From Bates' Guide (Chapter 5) – Key Elements
- Key elements of the clinical diagnostic reasoning process include data gathering, interpretation, hypothesis generation, hypothesis testing, and formulation of the diagnosis and plan. (Reference: Bates' Guide to Physical Examination and History Taking, 13e, 2021)
Dual Process Theory: Overview
- A cognitive framework describing two different types of thinking used in medical decisions and diagnoses.
System 1 (Fast, Intuitive)
- Characteristics: fast, intuitive, pattern recognition, used in familiar situations, relies on illness scripts.
System 2 (Slow, Analytical)
- Characteristics: slow, analytical, deliberate, more complex, used in unfamiliar situations, hypothesis testing.
How the Two Systems Interact
- Clinicians usually start with System 1 and move to System 2 as needed.
- System 1 saves time but is more susceptible to error and bias.
- System 2 is likely more accurate but slower and more resource-intensive in everyday practice.
- Experienced clinicians toggle between the two systems.
Illness Script: Definition and Purpose
- An organized mental summary of a disease a clinician has knowledge of.
- A structured summary based on experience and knowledge.
- Develops and evolves over time.
- Useful for comparing and contrasting disease processes.
- Pathophysiology
- Epidemiology
- Clinical Presentation (Signs and Symptoms)
- Diagnostics
- Management
- Format #1: Who? Why? Impetigo? When? What?
- Format #2: Pathophysiology; Epidemiology; Clinical Presentation (Signs and Symptoms); Diagnostics; Management
- Pathophysiology: Infection of the lower respiratory tract.
- Epidemiology: Older age, structural lung disease.
- Symptoms/Signs: Fever, cough, dyspnea for days, typically < 1 week.
- Diagnostics: Leukocytosis, infiltrate on chest X-ray support the diagnosis.
- Management: Antibiotics.
In-Class Illness Script Exercise (Impetigo)
- Take ~10 minutes in groups of 3–5 to create two Illness Scripts for Impetigo.
- Most commonly occurs in children 2–5 years of age.
- Spreads easily with close contact.
- Staph and Strep carriers.
- Warm, humid conditions.
- Broken skin—cuts, rash, bug bites.
- Crowding, poverty, poor hygiene.
- Carriers of Staph and Strep.
- Definition: Superficial bacterial infection of the skin.
- Pathogen: Staph aureus (Most common).
- Typical progression: Papules to pustules/vesicles then honey-colored crust.
- Typical distribution: Face and extremities.
- Contagious, superficial bacterial infection of the skin, Staph aureus (most common).
- Age group: 2–5 years.
- Key lesions: Papules to pustules/vesicles to honey-colored crust (nonbullous).
- Diagnostics: None or Gram stain of pus/exudate.
- Treatment: Topical antibiotics (Mupirocin) three times daily; oral antibiotics in some cases.
Illness Script: Basal Cell Carcinoma (BCC) – In-Class Exercise
- Take 5–10 minutes in groups of 3–5 to create one Illness Script for Basal Cell Carcinoma.
Illness Script: Basal Cell Carcinoma
- Pathophysiology
- Epidemiology
- Clinical Presentation (Signs and Symptoms)
- Diagnostics
- Management
Illness Script: In-Class Exercise (BCC) – Activity
- Create an illness script for Basal Cell Carcinoma.
Differential Diagnosis: Concepts and Principles
- Differential diagnosis is a method of analysis that distinguishes a disease or condition from others with similar clinical features.
- Clinicians must consider: likelihood, severity, and treatability of each potential diagnosis.
- The process is dynamic and changes as new information is gathered.
- Your differential before entering the room will change as you gather information via history and/or physical exam.
Can’t Miss Diagnoses
- Providers must always consider a “can’t miss” diagnosis.
- May require diagnostic testing to confirm absence of these conditions.
- Sample discussions: Chest pain, Dyspnea, Back pain.
Chest Pain Differential (Sample Differential)
- GERD (heartburn/acid reflux) or other GI issues
- Costochondritis or other musculoskeletal issues
- Anxiety or panic attacks
- Respiratory infections (influenza, COVID-19, pneumonia)
- Pneumothorax
- Pericarditis
- Pulmonary embolism
- Acute coronary syndrome
- Aortic dissection
Dermatology: Can’t Miss Dermatologic Conditions
- Melanoma
- Necrotizing Soft Tissue Infections (NSTI)
- Stevens-Johnson Syndrome (SJS)
- Toxic Epidermal Necrolysis (TEN)
Rash Case – Can’t Miss Diagnosis Example (SJS risk assessment)
- A 41-year-old female with a rash starting 1 day ago: what history questions help assess likelihood of SJS?
SJS/TEN Features
- Medication use
- Prodrome: fever, malaise, myalgias, sore throat, conjunctivitis, flu-like symptoms
- Mucosal involvement: oral cavity, nose, ear, genitals
- Ocular symptoms
Skin Lesion – Can’t Miss Diagnosis Example (Melanoma)
- A 55-year-old patient with a spot on the leg: what history questions help assess likelihood of melanoma?
Melanoma Risk Factors (Key Risks)
- New or changing lesion
- Change in size, shape, color
- Bleeding
- Personal or family history of skin cancer
- Excessive sun exposure, tanning bed use, history of sunburns
- VINDICATE categories:
- V: Vascular
- I: Infectious
- N: Neoplastic
- D: Degenerative
- I: Iatrogenic
- C: Congenital
- A: Autoimmune
- T: Traumatic
- E: Endocrine
VINDICATE Examples (Selected)
- Rash examples:
- V: Petechia, purpura
- I: Impetigo, viral exanthem, tinea
- N: Kaposi sarcoma
- D: NA
- I: Drug eruption/reaction
- C: Slate-gray nevi
- A: Lupus rash, psoriasis
- T: Abrasions, contact irritants
- E: Acanthosis nigricans
VINDICATE – Chest Pain Example
- V: Acute coronary syndrome
- I: Myocarditis
- N: Lung cancer
- D: Aortic stenosis
- I: Aortic dissection (post-cardiac instrumentation)
- C: Coarctation of the aorta
- A: Eosinophilic esophagitis
- T: Rib fracture
- E: Thyrotoxicosis
SPLIT: Differential Diagnosis (Skin Lesion)
- Serious (must not miss)
- Probable (most likely)
- Interesting (rare/zebra)
- Treatable (clinically actionable)
SPLIT Case: Skin Lesion
- S: Melanoma
- P: Seborrheic keratosis
- I: Trichofolliculoma
- T: Basal cell carcinoma
Justified Differential Diagnosis: What Justifies the List
- Information elicited that supports the diseases included in the differential
- Patient characteristics (age, gender, etc.)
- History findings (pertinent positives and negatives)
- Physical examination findings (pertinent positives and negatives)
- Laboratory and diagnostic testing results
- Justification leads to prioritization of differential diagnoses
- SHARP is a format used to assess clinical reasoning where the short-answer response to the most likely diagnosis is presented alongside the patient’s medical record.
- Learner selects the information from the record that best supports their decision; gray boxes in the example show the selected information.
- Abbreviations shown include BMI, BP, HEENT, HPV, Ht, O2 sat, RA, resp, etc.
Justified Differential Diagnosis: Application (SCFE Example)
- A 12-year-old male with a limp: in groups, create a differential diagnosis (5 items).
- Example output includes SCFE (slipped capital femoral epiphysis) as a key consideration.
Cognitive Biases in Medical Decision Making
- Definition: Cognitive biases are systematic errors in thinking that affect decisions and judgments.
- Many biases arise from overreliance on System 1 thinking.
- Biases are normal, predictable, and manageable.
Common Cognitive Biases
- Anchoring
- Availability bias
- Confirmation bias
- Premature closure
- Overconfidence bias
- Omission bias
- Commission bias
- Framing effect
- Outcome bias
Anchoring Bias (Definition and Example)
- Relying too heavily on an initial piece of clinical information.
- Example: A past medical history of panic disorder leads to missed acute coronary syndrome.
Availability Bias (Definition and Example)
- Judging probability based on recent experience.
- Example: Over diagnosing pulmonary embolism after a recent case.
Confirmation Bias (Definition and Example)
- Seeking data that supports a preconceived diagnosis; ignoring conflicting evidence.
Premature Closure (Definition and Example)
- Stopping diagnostic thinking too early before all evidence is gathered/verified.
Overconfidence Bias (Definition and Example)
- Overestimating one's diagnostic accuracy; discounting second opinions or guidelines.
Omission Bias, Commission Bias, Framing Effect, Outcome Bias
- Omission: Preferring inaction to action; fear of harm from treatment.
- Commission: Preferring action to inaction; e.g., antibiotics for viral illness “just in case.”
- Framing: Being swayed by how information is presented regarding risks/benefits.
- Outcome: Desiring a specific outcome that biases judgment (e.g., diagnosing X to avoid a complication).
Cognitive Bias Examples (Practice Scenarios)
- Case 1: 41-year-old with chest pain and shortness of breath; anxious with panic attack; ED diagnoses panic attack; Missed Pulmonary Embolism; Bias:
- Case 2: Febrile child labeled as “virus” without exam/tests; later develops sepsis; Bias:
- Case 3: 22-year-old with sore throat and tonsillar swelling diagnosed as strep pharyngitis; no further history or testing; risk of missing infectious mononucleosis (splenic rupture); Bias:
Strategies to Mitigate Cognitive Bias
- Metacognition: “Could I be wrong?” — pause to reflect.
- Clinical guidelines/Algorithms: Use clinical decision support tools.
- Second Opinions: Ask a colleague when uncertain.
- Diagnostic Time-outs: Step back when uncertain or case is atypical.
- Bias Awareness Training: CME or simulation scenarios.
Complexity and Uncertainty in Medical Practice
- There is no “answer key” in medicine.
- Medical knowledge is ever-increasing and evolving.
- Uncertainty is inevitable in clinical medicine.
- Quote: “Medicine is a science of uncertainty and an art of probability” — William Osler.
- Practical guidance:
- Accept uncertainty as part of the process.
- Do not focus solely on the right answer; work on decision making and clinical reasoning skills.
- Medicine involves problem-solving; there may not be one clear answer.
- Clinicians may say, “Sometimes we just don’t know.”
Development of Clinical Reasoning Skills at MWU
- OSCEs (Objective Structured Clinical Examinations)
- Case groups in Clinical Medicine III and IV
- Online clinical reasoning resources
- Aquifer (online clinical reasoning cases)
Aquifer Case: 68-year-old with a skin lesion
- Illustrates an online case used to practice differential diagnosis and reasoning.
References
- Clinical Reasoning, Assessment, and Plan. In: Bickley LS, Szilagyi PG, Hoffman RM, et al. eds. Bates' Guide to Physical Examination and History Taking, 13e. Lippincott Williams & Wilkins, 2021. Accessed July 08, 2025.
- Corrao S, Argano C. Rethinking clinical decision-making to improve clinical reasoning. Front Med (Lausanne). 2022;9:900543.
- OpenAI. ChatGPT (July 29, 2025 version) [large language model]. OpenAI. Accessed July 29, 2025.
- ten Cate O. Introduction. 2017 Nov 7. In: ten Cate O, Custers EJFM, Durning SJ, editors. Principles and Practice of Case-based Clinical Reasoning Education: A Method for Preclinical Students [Internet]. Cham (CH): Springer; 2018. Chapter 1. Available from: https://www.ncbi.nlm.nih.gov/books/NBK543763/
- Witt EE, Onorato SE, Schwartzstein RM. Medical students and the drive for a single right answer: teaching complexity and uncertainty. ATS Scholar. 2021;3(1):27-37.