--- module: 006-01 language: en chapter: 6 title: "Clinical Reasoning, History, Examination, and Diagnostic Probability" module_title: "Foundations" source_sha256: 069c1a1e5a49cc929b6983226e4df0b3c0ecd907785ac8252a73bc2d357fa7ed --- # Clinical reasoning, history and examination ## Safety and context first ### Is the patient unstable #### Airway, work of breathing, oxygenation #### Circulation, mental state, temperature #### Severe pain, active bleeding ### Primary survey runs alongside resuscitation ### Stabilisation and diagnosis proceed together ### Context changes probability #### Age, pregnancy, immune status #### Recent surgery, travel, occupation #### Medicines, devices, prior disease ## History of the presenting problem ### Open question first, then focused ### Onset, site, character, severity, radiation ### Timing, progression, precipitants, relievers ### Chronology is often diagnostic #### Sudden maximal: vascular, rupture, obstruction, arrhythmia, seizure, pneumothorax #### Episodic: intermittent obstruction, migraine, mediator release, exposure #### Progressive: structural disease, neurodegeneration, malignancy, organ failure ### Ideas, concerns and expectations ### Effect on sleep, work, mobility, self-care ## Background and medicines ### Severity, complications, control, not labels ### Family history: inherited disease, premature vascular events ### Social history: supports, occupation, substances, exposures ### Medication history #### Dose, route, timing, indication #### Adherence, benefit, adverse effects, recent changes #### Over-the-counter and complementary products ### Allergy: name the actual reaction ### Review of systems tests the differential, not everything ## Examination as hypothesis testing ### Consent, dignity, chaperone, infection control ### Observe before touching ### Vital signs read as a pattern, not single values ### Link every sign to anatomy and mechanism #### Raised jugular venous pressure depends on technique #### Crackles are not specific to one disease #### Separate weakness from pain, effort, fatigue ### Reliability varies: a sign shifts probability ## Problem representation ### Demographics, time course, key syndrome ### Major risk factors and discriminating findings ### Compression that keeps the inconvenient finding ## Differential by mechanism and anatomy ### Vascular, infective, inflammatory, neoplastic ### Degenerative, toxic, metabolic, endocrine ### Traumatic, obstructive, iatrogenic, congenital, functional ### Priority questions #### Most likely #### Most dangerous if missed #### Most treatable or time-sensitive ## Probability and diagnostic tests ### Pre-test probability from prevalence, setting, risk, findings ### Sensitivity: proportion with disease testing positive ### Specificity: proportion without disease testing negative ### Likelihood ratio shifts the odds ### Predictive value depends on prevalence #### Rare disease yields false positives in excess #### Very high probability survives a negative result ### Most informative near a decision threshold ### Reference interval is a distribution, not a boundary ## Cognitive error and calibration ### Anchoring and premature closure ### Confirmation bias and search satisfaction ### Base-rate neglect and framing ### Diagnostic pause #### What else could this be #### Which finding does not fit #### What evidence would change the plan ### Calibration: state residual probability, not exclusion ### Follow-up is a diagnostic tool ## Documentation and communication ### Source and reliability of information ### Relevant positives and negatives, uncertainty, plan ### Handover: situation, background, risk, recommendation ### Closed-loop communication on critical instructions ### Shared decision-making and decision-specific capacity