Preparatory Mindset
Diagnostics is the bridge between basic sciences and clinical medicine. It is built on "Three basics + thinking" — basic theory, basic knowledge, basic skills, plus clinical thinking. The two halves of the subject are: (1) Clinical skills — history taking, symptom analysis, and physical examination (inspection, palpation, percussion, auscultation, olfaction); and (2) Laboratory & instrumental diagnostics — lab tests, ECG, imaging, and endoscopy. Diagnosis is a process: gather data → analyze → form a working hypothesis → verify or revise. Good diagnosis = medical knowledge + clinical experience + scientific thinking.
Core Concepts
What is Diagnosis?
Diagnosis uses symptoms, signs, laboratory tests, and special examinations as clues to find a clinically reasonable explanation for the patient's discomfort. In the words of Zhang Zhongjing: 观其脉证，知犯何逆，随证治之. Only an accurate diagnosis can guide correct treatment — an incorrect diagnosis can harm the patient.
- Clinical Thinking (临床思维): the physician's worldview/methodology for analyzing patient data to make diagnostic and therapeutic decisions
- Critical Thinking (批判性思维): evaluating evidence, identifying bias, assessing quality of information
- Clinical Reasoning (临床推理): logical inference, hypothesis formation, evidence evaluation
- Clinical Judgment (临床判断): the final decision based on reasoning
The Diagnostic Process — 4 Steps
| Step | Content | Key points |
|---|---|---|
| 1. Gathering clinical data | History taking + physical exam + initial lab/ancillary tests | History is the single largest contributor (about 50% of diagnoses); PE ~30%; instrumental ~20% |
| 2. Analysis & synthesis | Evaluate facts, identify key problems, form hypotheses | Reliable data in → reliable diagnosis out |
| 3. Preliminary diagnosis | Working hypothesis based on most-likely explanation | Probabilistic, not absolute truth |
| 4. Verification / revision | Test with clinical course, treatment response, new results | Diagnosis is dynamic and always revisable |
Seven Principles of Clinical Thinking
- Common diseases first — prioritize common/frequent diseases (Bayesian reasoning). A smoker's cough + SOB is more likely bronchitis/COPD than a rare fungal infection.
- Organic over functional — missing organic disease causes irreversible harm; functional diagnosis is one of exclusion (e.g. chest pain must rule out CAD before attributing to neurosis).
- Treatable diseases first — a lung shadow with hemoptysis should be treated as TB (treatable) while lung cancer is being ruled out.
- Consider local epidemics — fever + arthralgia + travel history → consider dengue/chikungunya.
- Single diagnosis to explain all symptoms — lung cancer with syncope + intracranial mass → brain metastasis, not a separate primary tumor.
- Be objective and factualistic — avoid anchoring and confirmation bias; follow the data.
- Treat the patient, not just the disease — biological + psychological + social factors; symptoms ≠ disease severity.
Characteristics of Clinical Reasoning
- Complexity of subject: human body variability, subjective patient reports, physician integration
- Urgency of time: in MI/stroke/sepsis, compress the process — targeted history/exam, only immediately-actionable tests
- Incompleteness of information: disease evolution + setting constraints → decide on incomplete data
- Probabilistic nature: initial diagnoses are working hypotheses, not certainties
- Dynamic evolution: diagnosis is a "tentative label" confirmed/revised by course and response
History Taking — Basic Structure
- General data (name, age, sex, occupation, address, nationality, recording date, informant, reliability)
- Chief complaints (主诉) — symptom/sign + duration, 1–2 sentences
- Present illness history (现病史) — onset, characteristics, inducing factors, development, associated symptoms, previous treatment, general condition
- Past history (既往史) — previous health, infections, operations, trauma, allergies, immunizations
- Review of systems (系统回顾) — GI, cardiorespiratory, neuro, urinary, etc.
- Personal/social history (个人史) — work, smoking, alcohol, travel
- Marital history (婚姻史)
- Menstrual & childbearing history (月经生育史)
- Family history (家族史)
The 73855 Magic Number in Communication
- Words 7% / Tone 38% / External image & body 55%
- Active listening, empathy, eye contact, simple language, patient-centered (disease framework + illness framework)
High-Yield Points
- 50% of diagnoses come from history alone, 30% from PE, 20% from investigations
- 5 basic PE methods: inspection, palpation, percussion, auscultation, olfaction (视触叩听嗅)
- Chief complaint = symptom/sign + duration, never a diagnosis
- Present illness must include: onset, characteristics, aggravating/relieving factors, associated symptoms, prior treatment, general condition
- Common > rare, organic > functional, treatable first, single diagnosis, objective, patient not disease
- Chest pain case: history questions must cover location, quality, onset, severity, radiation, aggravating/relieving factors, associated symptoms (crushing + radiation to left arm → cardiac)
- Communication: informed consent, empathy, privacy, never rush, don't over-note-take
LMCHK OSCE Practice
- 3C1H before any examination: Consent (「你好，我是XX醫生，今天要幫你做一個XX檢查，請問你同意嗎？」), Curtain (blinds for privacy), Chaperone (opposite-sex patient → "I would like to have a chaperone"), Hygiene ("Hand wash").
- Running commentary script: introduce yourself → state consent/curtain/chaperone/hand hygiene → adjust bed position and exposure → ask about pain ("先生，有沒有哪裡痛？") → "I will do the examination; please tell me if anything is uncomfortable."
- OSCE station structure (LMCHK Part 3): Medicine short case = 2 stations × 20 min (Station 1: Abdomen 8 min + CVS 8 min + General 4 min; Station 2: Respiratory 8 min + Neurology 8 min + General 4 min). Written tasks may be part of a station.
- General medicine station: dermatology (erythroderma), rheumatology (rheumatoid hand, ankylosing spondylitis), endocrinology (Cushing, acromegaly), spot diagnosis.
Topic Summary
Diagnostics = history + symptoms/signs + physical examination + laboratory/instrumental examination + clinical thinking. The 4-step diagnostic process turns raw clinical data into a verified diagnosis. Master the 7 thinking principles and the full history-taking framework, and you have the skeleton for every clinical encounter — both in ward practice and in LMCHK OSCE short/long cases.