History Taking for Chest Pain

1. Stabilise First

• Abnormal vital signs
• ECG signs of ischaemia/injury
• Prior coronary artery disease
• Abrupt, severe, or new-onset chest pain (Tintinalli's Emergency Medicine)

2. The Core SOCRATES Framework

3. Differential-Directed Questioning

Acute Coronary Syndrome (ACS / Angina / MI)

• Classic: Retrosternal crushing/squeezing/pressure; radiation to left arm (or both arms), neck, or jaw; brought on by exertion; relieved by rest or nitrates; lasts 2–10 min (stable), >30 min (AMI)
• Key associated features: Diaphoresis, nausea, dyspnoea
• Non-classic (do NOT dismiss): Sharp or stabbing quality occurs in 22% of AMIs; pleuritic, positional, or very brief pain does not exclude ACS
• High-risk groups for atypical presentation: Women (especially pre/early menopausal), elderly, diabetics, racial minorities, psychiatric illness — may present with fatigue, nausea, jaw/neck/back pain without chest pain
• Anginal equivalents (47% of MI patients present without classic chest pain): Dyspnoea, epigastric discomfort, generalised weakness, diaphoresis, palpitations, acute confusion (Tintinalli's Emergency Medicine; Goldman-Cecil Medicine)

Aortic Dissection

• Sudden onset, maximal-severity "tearing" or "ripping" pain
• Radiation to the back (ascending → chest/back; descending → back/abdomen)
• History of hypertension, Marfan syndrome, connective tissue disorder, cocaine use, pregnancy
• Ask about pulse asymmetry, neurological symptoms, arm BP difference (Goldman-Cecil Medicine)

Pulmonary Embolism (PE)

• Pleuritic — sharp, worsened by deep inspiration
• Associated with dyspnoea, haemoptysis, leg swelling/DVT
• Risk factors: Immobilisation, recent surgery/travel, OCP, pregnancy, malignancy, blood dyscrasias (Murray & Nadel's Respiratory Medicine)

Pericarditis

• Sharp retrosternal pain, relieved by sitting up and leaning forward, worsened lying flat
• May radiate to trapezius ridge
• Recent viral illness, fever (Goldman-Cecil; Murray & Nadel)

Tension Pneumothorax / Spontaneous Pneumothorax

• Sudden-onset pleuritic pain, ipsilateral
• Young tall male or underlying lung disease (COPD, asthma, Marfan) (Murray & Nadel's)

Pleuritis / Pneumonia

• Pleuritic pain (worsened by deep breath, cough, sneezing) — localised, unilateral
• Diaphragmatic pleurisy → referred to ipsilateral shoulder and neck
• Associated fever, productive cough (Murray & Nadel's)

Musculoskeletal

• Point tenderness reproduced by palpation or specific movement
• Tietze syndrome: costochondral junction redness/swelling
• Precordial catch (Texidor's twinge): sharp, left apical, resolves in minutes
• Intercostal neuritis/herpes zoster: lancinating, dermatomal, look for vesicular rash 1–2 days later (Murray & Nadel's; Rosen's EM)

Gastrointestinal (Oesophageal / GI)

• Burning character, worse after meals, relieved by antacids → GORD
• Oesophageal spasm can mimic angina exactly — even relieved by nitrates
• Epigastric pain in >50-year-olds or known CAD: always include ECG (may be ACS) (Goldman-Cecil; Rosen's)

4. Past Medical History

• Established IHD, prior MI, stents, CABG, previous angiogram/stress test results
• Prior identical episodes — what was the cause?
• Hypertension, hypercholesterolaemia, diabetes, atrial fibrillation
• Previous PE or DVT
• Known aortic aneurysm or connective tissue disease
• Active malignancy

5. Medications

• GTN — does it relieve the pain, and how quickly?
• Anticoagulants, antiplatelets
• OCP (PE risk)
• Cocaine, amphetamines (ACS risk even in young patients)
• Antiretrovirals (accelerated atherosclerosis)

6. Family History

• Early sudden cardiac death in young adulthood
• Premature coronary artery disease
• Inherited conditions: Marfan syndrome, hypertrophic cardiomyopathy, channelopathies

7. Social History

• Smoking (pack-years)
• Cocaine or other recreational drug use
• Recent travel or prolonged immobilisation (PE)
• Occupation, physical activity level

8. Features That Increase or Decrease ACS Likelihood

Note: No single symptom rules ACS in or out. Use clinical gestalt integrating all features, risk factors, ECG, and troponins.

9. Risk Stratification Scores to Recall

• HEART score (History, ECG, Age, Risk factors, Troponin) — widely validated in ED chest pain
• TIMI score — for NSTEMI/UA
• Wells score — for PE
• ADD-RS / aortic dissection risk score — for dissection

10. Special Populations

• Women: More atypical presentations; back pain, fatigue, jaw pain, nausea predominate
• Elderly: Higher rates of silent ischaemia; dyspnoea may be the only complaint
• Diabetics: Autonomic neuropathy blunts pain perception
• Children/Adolescents: Most common causes are musculoskeletal, asthma, GORD; cardiac causes (HCM, anomalous coronaries) present with exertional chest pain or syncope on exertion — always ask about family history of sudden unexplained death (Rosen's EM)

The Master History-Taking Framework

STEP 1 — Opening

• Introduce yourself, confirm patient identity
• Open question: "What brings you in today?" / "Tell me what's been happening."
• Listen without interrupting for at least 60 seconds — let the patient tell their story
• Acknowledge and empathise before probing

STEP 2 — Presenting Complaint (PC)

e.g., "Chest pain × 2 hours"

STEP 3 — History of Presenting Complaint (HPC)

Always ask: "Is this the first time?" and "Have you ever had anything like this before?"

STEP 4 — Systematic Associated Symptoms Review

Cardiovascular

• Chest pain, palpitations, dyspnoea, orthopnoea, PND, ankle swelling, syncope, claudication

Respiratory

• Cough (dry/productive), haemoptysis, wheeze, dyspnoea, pleuritic pain, night sweats

Gastrointestinal

• Nausea, vomiting, dysphagia, heartburn, abdominal pain, change in bowel habit, PR bleeding, melaena, jaundice, weight loss

Genitourinary

• Dysuria, frequency, urgency, haematuria, discharge, menstrual history (in women — LMP, cycle regularity, pregnancies), testicular pain/swelling

Neurological

• Headache, visual changes, diplopia, dizziness, vertigo, weakness, numbness, speech disturbance, seizures, memory problems, gait disturbance

Musculoskeletal

• Joint pain/swelling, stiffness (morning), muscle pain/weakness, back pain, functional limitation

Endocrine / Constitutional

• Weight change, fatigue, heat/cold intolerance, polydipsia, polyuria, hair/skin changes, menstrual irregularity

Haematological

• Easy bruising/bleeding, lymph node swelling, recurrent infections, pallor

Psychiatric

• Mood (low/elevated), anxiety, sleep disturbance, appetite, suicidal ideation (ask directly and sensitively)

Skin

• Rashes, lesions, pruritus, colour change, wounds

STEP 5 — Past Medical History (PMH)

• Previous illnesses, diagnoses, hospital admissions
• Previous surgeries or procedures
• Previous similar episodes
• Chronic conditions (HTN, DM, IHD, COPD, CKD, thyroid, epilepsy, etc.)
• Psychiatric history
• Obstetric history (women): G_P_, complications, current pregnancy?
• Childhood illnesses if relevant

"Have you ever been in hospital before? Do you have any ongoing medical conditions?"

STEP 6 — Drug History (DH)

• All current medications — name, dose, frequency, route, how long
• OTC medications, herbal remedies, supplements
• Allergies — drug, food, environment; what reaction did they have? (distinguish true allergy from intolerance)
• Compliance — are they actually taking their medications?
• Recreational drugs (ask non-judgementally: "Do you use any recreational substances?")

STEP 7 — Family History (FH)

• Health of parents, siblings, children — alive or deceased? Cause of death?
• Specific inherited conditions relevant to the complaint:
  • Cardiovascular: premature IHD, sudden unexplained death, cardiomyopathy, arrhythmia
  • Cancer: type, age of onset
  • Metabolic: DM, thyroid, hyperlipidaemia
  • Neurological: epilepsy, dementia, movement disorders
  • Haematological: thrombophilia, bleeding disorders

"Is there anything that runs in your family?"

STEP 8 — Social History (SH)

STEP 9 — Ideas, Concerns, Expectations (ICE)

• Ideas: "What do you think might be causing this?"
• Concerns: "Is there anything specific you're worried about?"
• Expectations: "What were you hoping we might be able to do for you today?"

STEP 10 — Summarise and Screen

• Summarise back to the patient: "So to make sure I've understood correctly…"
• Screen: "Is there anything else you'd like to tell me or that you think I should know?"
• Safety-net: Identify any red flags you may have missed

Red Flag Symptoms — Never Miss These

Structuring Your Findings

PC:     One-line summary
HPC:    Chronological narrative using SOCRATES
PMH:    Bullet list
DH:     All meds + allergies
FH:     Relevant positives and negatives
SH:     Smoking, alcohol, drugs, occupation, living situation
ROS:    Positive and relevant negative findings
ICE:    Patient's perspective

The Golden Habits

1. Start open, then funnel — broad open questions → specific closed questions
2. Follow the patient's lead — let them complete sentences
3. Clarify lay terms — what does the patient mean by "dizzy"? (vertigo vs presyncope vs light-headedness)
4. Silence is a tool — pause after open questions; patients often continue with the most important detail
5. Non-verbal cues — notice body language, affect, distress
6. Avoid leading questions — not "Is it a crushing pain?" but "How would you describe it?"
7. Age and sex adjust — think about what conditions are most likely in this demographic
8. When in doubt, ask again — "Tell me more about that"

Differential Diagnosis, Provisional Diagnosis & How to Present a History

PART 1 — How to Build a Differential Diagnosis (DDx)

Step 1 — Extract the "Problem Representation"

"A [age]-year-old [sex] with [key risk factors] presenting with [duration] of [key symptoms] and [key associated features]."

"A 55-year-old hypertensive male smoker presenting with 2 hours of crushing central chest pain radiating to the left arm, associated with diaphoresis and nausea."

Step 2 — Generate the DDx Using a System

Method A — Anatomical / Regional

Method B — Surgical Sieve (VITAMINS C)

Method C — Probability Triage (Always Do This)

Step 3 — Weight Each Diagnosis Using Clinical Features

Step 4 — Rank Your List

PART 2 — How to Formulate the Provisional Diagnosis

The Formula:

Provisional diagnosis = Most likely condition that:

• Explains all (or most) key features
• Fits the demographics and risk factors
• Accounts for the time course
• Is biologically plausible

How to State It:

"My provisional diagnosis is STEMI, based on the acute onset of crushing central chest pain radiating to the left arm with diaphoresis and nausea in a 55-year-old hypertensive male smoker, lasting over 30 minutes."

The Provisional Diagnosis Statement Has 3 Parts:

1. WHAT:   "My provisional diagnosis is [condition]"
2. WHY:    "...based on [key supporting features from history/exam/results]"
3. CAVEAT: "...however I want to exclude [must-not-miss alternatives] with [specific tests]"

"My provisional diagnosis is acute STEMI, based on the clinical presentation of acute central crushing chest pain with radiation, diaphoresis, and risk factors. However, I want to exclude aortic dissection with a chest X-ray and CT angiogram, and PE with a D-dimer and CT-PA if indicated."

PART 3 — How to Present a History

The Golden Rules of Presentation

1. Speak in sentences, not bullet points
2. Lead with the most important information
3. Be concise but complete — include all positives and relevant negatives
4. Maintain logical flow — chronological within HPC
5. End with your assessment — DDx and provisional diagnosis
6. Do not pad — avoid filler words; every sentence should add information

The Optimal Presentation Structure

🔹 1. Opening Line (10 seconds)

"Mr Ahmed is a 55-year-old hypertensive male smoker who presents with a 2-hour history of chest pain."

🔹 2. History of Presenting Complaint (60–90 seconds)

"The pain started suddenly at rest, is central and crushing in character, radiating to the left arm. It is associated with diaphoresis and nausea, and he rates the severity as 9 out of 10. It has been constant for the past 2 hours, worsening over time, and has not been relieved by antacids or positional change. There is no pleuritic component and no associated cough or haemoptysis."

• State positive features first
• Then state relevant negatives — these are as important as positives
• Relevant negatives are the features you asked about specifically because they affect the DDx

"Notably, there is no tearing quality to suggest dissection, no fever or recent viral illness to suggest pericarditis, and no leg swelling or recent immobilisation to suggest PE."

🔹 3. Past Medical History (15 seconds)

"His past medical history is significant for hypertension and hypercholesterolaemia. He had no prior cardiac events. He underwent an appendicectomy in 2005."

🔹 4. Drug History + Allergies (10 seconds)

"He takes amlodipine 10 mg once daily and atorvastatin 40 mg. He has a documented penicillin allergy causing rash."

🔹 5. Family History (5–10 seconds)

"His father died of a myocardial infarction aged 58."

🔹 6. Social History (10–15 seconds)

"He is a 30-pack-year smoker. He drinks approximately 10 units of alcohol per week. He is a taxi driver and lives with his wife. He is independent in all activities of daily living."

🔹 7. Systems Review (10 seconds)

"On systems review, he denies dysphagia, abdominal pain, or recent weight loss."

🔹 8. Summary Statement (15–20 seconds)

"In summary, this is a 55-year-old hypertensive male smoker presenting with a 2-hour history of acute crushing central chest pain radiating to the left arm with diaphoresis and nausea, in the context of a family history of premature coronary artery disease."

🔹 9. Differential and Provisional Diagnosis (30 seconds)

"My provisional diagnosis is an acute ST-elevation myocardial infarction. My differential includes unstable angina, aortic dissection — which I consider less likely given the absence of a tearing quality or back pain — and pulmonary embolism, which is unlikely given no pleuritic features or DVT risk factors."

🔹 10. Proposed Investigations and Management

"I would like an urgent 12-lead ECG, troponin, FBC, U&E, LFTs, coagulation screen, chest X-ray, and group and save. If ECG confirms STEMI, I would activate the cardiac catheterisation lab and commence dual antiplatelet therapy, anticoagulation, and oxygen if saturations are below 94%."

Full Example: Putting It All Together

"Mr Ahmed is a 55-year-old hypertensive male smoker who presents with a 2-hour history of crushing central chest pain.

The pain began suddenly at rest, is rated 9/10 in severity, and is described as crushing in character. It radiates to the left arm and is associated with diaphoresis and nausea. It has not been relieved by rest. There is no tearing quality, no pleuritic component, no cough, haemoptysis, or leg swelling. He has not had similar pain before.

His past medical history includes hypertension and hypercholesterolaemia. He takes amlodipine and atorvastatin. He has a penicillin allergy. His father died of an MI at age 58. He is a 30-pack-year smoker and drinks 10 units of alcohol per week. He is a taxi driver, lives with his wife, and is fully independent.

In summary, this is a high-risk patient with multiple cardiovascular risk factors presenting with a classic acute coronary syndrome picture.

My provisional diagnosis is acute STEMI. My differentials include unstable angina, aortic dissection — less likely given absence of tearing pain or back radiation — and PE, which is unlikely given no pleuritic features or immobilisation history.

I would like an urgent ECG, troponin, chest X-ray, and routine bloods. If STEMI is confirmed on ECG, I would activate the cath lab immediately."

Quick Reference Card

PRESENTATION ORDER:
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
1. Opening line      → Age, sex, PMH, complaint, duration
2. HPC               → SOCRATES narrative + relevant negatives
3. PMH               → Relevant conditions first
4. DH + Allergies    → Medications + reactions
5. FH                → Only if relevant
6. SH                → Smoking, alcohol, occupation, function
7. Systems review    → Key positives/negatives only
8. Summary           → 2-3 sentence synthesis
9. DDx + Provisional → Ranked with reasoning
10. Plan             → Investigations + Management
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

DDx FORMULA:
Must-not-miss → Most likely (Provisional) → Also consider

PROVISIONAL Dx FORMULA:
"My provisional diagnosis is [X], based on [features A, B, C],
 however I want to exclude [Y] with [test Z]."

Mnemonics & Formulas for HoPI by Chief Complaint

Every complaint uses SOCRATES as the base. What follows are the extra targeted questions unique to each complaint — the ones that make the difference in diagnosis.

THE MASTER BASE (Always First)

S — Site
O — Onset
C — Character
R — Radiation
A — Associated symptoms
T — Timing
E — Exacerbating / Relieving factors
S — Severity

1. CHEST PAIN — "PQRST + AWED"

P — Provocation / Palliation (exertion? rest? nitrates? antacids? position?)
Q — Quality (crushing, tearing, burning, stabbing, pleuritic)
R — Radiation (arm, jaw, back, shoulder)
S — Severity + Sweating (diaphoresis = cardiac until proven otherwise)
T — Timing (seconds = MSK; minutes = angina; hours = MI/PE/dissection)

A — Associated: dyspnoea, nausea, palpitations, syncope
W — Worse with: breathing (pleuritic), movement (MSK), meals (GI)
E — Exertion history: does it come on walking? How far?
D — DVT/dissection risk: travel, immobilisation, hypertension, Marfan

• Tearing + back pain → Dissection
• Pleuritic + dyspnoea + DVT risk → PE
• Positional + leaning forward relieves → Pericarditis
• Post-meal + burning → GORD/oesophageal
• Reproducible on palpation → MSK

2. DYSPNOEA (Shortness of Breath) — "AMPLE PODS"

A — Acuity: sudden (pneumothorax, PE, flash pulmonary oedema) vs gradual (heart failure, COPD)
M — Modified MRC scale: how many stairs/metres before stopping?
P — Posture: orthopnoea (pillows at night)? PND (wakes up gasping)?
L — Lying flat: worse = LVF; better lying = COPD/asthma
E — Exertion threshold: walking on flat? At rest?

P — Precipitants: allergen, exercise, cold, infection, emotion
O — Other symptoms: wheeze, cough, haemoptysis, chest pain, ankle swelling, fever
D — Duration of each episode
S — Sputum: colour, quantity (yellow/green = infection; pink frothy = pulmonary oedema)

• Orthopnoea + PND + ankle oedema → Heart failure
• Wheeze + atopy + triggers → Asthma
• Chronic smoker + progressive → COPD
• Sudden + pleuritic + risk factors → PE
• Sudden + young + no trigger → Pneumothorax

3. PALPITATIONS — "SCRIPT"

S — Start and Stop: sudden (SVT/AF) vs gradual (sinus tachycardia)?
C — Character: fast/slow? Regular/irregular? "Racing", "flip-flopping", "thudding"?
R — Rate: can they tap it out?
I — In between episodes: any symptoms at rest?
P — Precipitants: caffeine, alcohol, exercise, stress, fever, thyroid meds
T — Termination: stops suddenly (SVT) or gradually (sinus tach)? Valsalva? Water?

• Syncope or pre-syncope with palpitations → Dangerous arrhythmia (VT, WPW)
• Chest pain during palpitations → Ischaemia
• Thyroid symptoms (heat intolerance, weight loss) → AF secondary to hyperthyroidism
• Family history of sudden death → Channelopathy (LQTS, Brugada)

4. HEADACHE — "POUND + 3Ss"

P — Pulsatile quality?
O — One-day duration (4–72 hrs)?
U — Unilateral?
N — Nausea / vomiting?
D — Disabling (stops activity)?
→ (≥4 of 5 = migraine with high specificity)

3Ss — Screen for Danger:
S — Sudden onset / Thunderclap ("worst headache of my life") → SAH
S — Systemic features: fever, rash, neck stiffness → Meningitis
S — Secondary features: neurological deficit, papilloedema, postural, progressive → Space-occupying lesion

• Morning headache + worsened by Valsalva → Raised ICP
• Temporal tenderness + jaw claudication + age >50 → Giant Cell Arteritis
• Unilateral + eye redness/watering + autonomic features → Cluster headache
• Better with caffeine/in dark/quiet → Migraine
• Postural (worse standing, better lying) → Intracranial hypotension

5. ABDOMINAL PAIN — "SOCRATES + DOMVIT"

D — Diarrhoea / Constipation: onset, frequency, blood, mucus?
O — Open bowels: last time? Flatus passing?
M — Meals: relation to eating (before = peptic; after = biliary/ischaemic)?
V — Vomiting: blood (haematemesis)? Bile? Faeculent?
I — Investigations: prior endoscopy, scans, operations?
T — Travel: recent foreign travel → infectious cause

L — Last menstrual period
O — Obstetric history (G_P_)
S — Sexual history / contraception
S — Spotting or vaginal discharge

6. VOMITING / NAUSEA — "VITAMIN FO"

V — Volume: how much each episode?
I — Is there blood? (haematemesis — red = fresh; coffee grounds = altered)
T — Timing: relation to meals? Morning (pregnancy, ↑ICP, alcohol)?
A — Associated: pain, fever, diarrhoea, headache, vertigo, jaundice?
M — Medications: NSAIDs, opioids, chemotherapy, digoxin?
I — Ingestion: food, alcohol, toxins?
N — Neurological: headache, visual changes (raised ICP)?

F — Frequency per day
O — Other: last normal meal, bowel activity, urine output (dehydration assessment)

7. DIARRHOEA — "FLOATS"

F — Frequency: how many times per day? Change from baseline?
L — Looks: watery, bloody, mucusy, oily/fatty (steatorrhoea), pale?
O — Onset: acute (<2 weeks = infective/toxic) vs chronic (>4 weeks = IBD/IBS/malabsorption)
A — Associated: pain (before or relieved by defecation?), urgency, tenesmus, weight loss, fever
T — Travel / contacts: anyone else affected? Recent antibiotics (C. diff)?
S — Systemic: weight loss, mouth ulcers, joint pain, eye symptoms, skin rashes (IBD clues)

• Bloody + mucus + tenesmus → IBD / infective colitis
• Watery + no blood + post-antibiotic → C. difficile
• Fatty + weight loss + malabsorption → Coeliac / pancreatic insufficiency
• Relieved by defecation + alternating → IBS
• Nocturnal diarrhoea → Organic (not IBS)

8. JAUNDICE — "JAUNDICE"

J — Joint pain / arthralgia (viral hepatitis)
A — Abdo pain: RUQ (biliary) vs painless (malignancy = Courvoisier's)
U — Urine colour: dark (obstructive/hepatic) vs normal (haemolytic)
N — Nausea, vomiting, fever (hepatitis, cholangitis)
D — Duration and progression
I — Itch (pruritus = obstructive jaundice)
C — Contacts, travel, sexual history, blood transfusions (hepatitis risk)
E — Exposure: alcohol (quantity), drugs/medications, toxins, herbal remedies

• Pale stools + dark urine + itch = Obstructive (cholestatic)
• Normal stools = Hepatocellular or haemolytic

9. DYSURIA / URINARY SYMPTOMS — "FLOSS FUND"

F — Frequency
L — Lower urinary tract symptoms: urgency, nocturia, hesitancy, poor stream, incomplete emptying
O — Output: oliguria / polyuria?
S — Stinging / burning on micturition
S — Smell / appearance: cloudy, haematuria, frothy

F — Fever / rigors (systemic → pyelonephritis vs lower UTI)
U — Urethral discharge
N — Nausea / flank pain (loin = upper tract)
D — Duration

• Prostate symptoms: hesitancy, terminal dribbling, incomplete emptying, double voiding → BPH / prostate cancer
• Testicular pain / swelling → Epididymo-orchitis, torsion

10. HAEMATURIA — "ABCDE of Haematuria"

A — Amount: gross (visible) vs microscopic?
B — Blood timing: start of stream (urethra) / end of stream (bladder neck/prostate) / throughout (kidney/ureter)
C — Clots? Shape: worm-like = ureter; amorphous = bladder
D — Dysuria / lower urinary symptoms?
E — Elsewhere: weight loss, bone pain, cough (malignancy)?

11. BACK PAIN — "BACK + RED FLAGS"

B — Body of pain: thoracic (serious until proven otherwise) vs lumbar vs sacral?
A — Activity: worse with movement (MSK) vs rest (inflammatory/malignancy)?
C — Character: dull ache vs sharp vs band-like?
K — Kick: radiation down the leg? Below knee? (sciatica = nerve root)

RED FLAGS (must ask every time):
- Age <20 or >55 with new back pain
- Trauma history
- Fever / weight loss (infection/malignancy)
- Night pain waking from sleep (malignancy, AS)
- Bilateral leg symptoms or saddle anaesthesia → Cauda Equina (EMERGENCY)
- Bladder/bowel dysfunction → Cauda Equina
- History of malignancy / steroids / immunosuppression

12. JOINT PAIN — "JOINT + SPARE"

J — Joint count: monoarthritis (1) / oligoarthritis (2-4) / polyarthritis (≥5)?
O — Onset: acute (hours = septic/gout/trauma) vs subacute/chronic?
I — Inflammatory vs mechanical?
    Inflammatory: morning stiffness >1hr, worse with rest, better with activity
    Mechanical: worse with activity, better with rest, no morning stiffness
N — Number and pattern: symmetric (RA) / asymmetric (reactive/psoriatic) / large (OA/gout) / small (RA)?
T — Temperature: hot, red, swollen = septic or crystal arthropathy

S — Stiffness: duration in morning?
P — Prior episodes / triggers: recent infection (reactive), dietary (gout), trauma?
A — Associated: rash (psoriasis, SLE), eye (uveitis), bowel (IBD, reactive), urethral discharge (reactive)?
R — Rest: does rest help or worsen?
E — Extra-articular features: fatigue, fever, weight loss, mouth ulcers, Raynaud's

13. SYNCOPE / COLLAPSE — "COLLAPSE"

C — Circumstances: standing (vasovagal/orthostatic) / exertion (cardiac) / sitting (cardiac)
O — Others witnessed it? What did they see? Duration of loss of consciousness?
L — Limb jerking / tongue biting / incontinence (seizure vs syncope)
L — Lies down / recovery: fast full recovery (vasovagal) vs prolonged confusion (seizure/Todd's)
A — Aura / prodrome: nausea, sweating, tunnel vision (vasovagal) vs no warning (cardiac/arrhythmia)
P — Palpitations before or after?
S — Stimuli: pain, emotion, blood, prolonged standing, micturition, cough?
E — Exertion: during or immediately after exercise → **Cardiac (HCM, LQTS, aortic stenosis)**

14. SEIZURE — "BEFORE + DURING + AFTER"

BEFORE (Aura/Prodrome):
- Warning? Type: visual, smell (uncinate), déjà vu, rising epigastric feeling?
- Triggers: sleep deprivation, alcohol, flashing lights, fever?

DURING (Ictal phase — from witness):
- Duration?
- Movement: tonic-clonic, focal, staring, automatisms?
- Eyes: open or closed? Deviation?
- Colour: cyanosis, pallor?
- Tongue biting (lateral = seizure; tip = syncope)
- Incontinence?

AFTER (Post-ictal):
- Confusion duration (Todd's paresis)?
- Headache? Muscle aching?
- Memory of event?

15. COUGH — "COUGHS"

C — Character: dry / productive / barking (croup) / whooping?
O — Onset: acute <3 weeks (infective) / subacute 3-8 weeks / chronic >8 weeks
U — Urge: constant or episodic? Nocturnal (asthma, LVF, GORD)?
G — Green / yellow sputum vs clear vs blood (haemoptysis)?
H — Haemoptysis: amount, frequency, mixed with sputum or pure blood?
S — Smoking history + ACE inhibitor use (dry cough side effect)

C — Chest pain / Cancer risk
L — Last episode
A — Amount (teaspoon vs cupful = massive)
M — Medications: anticoagulants?
P — Prior TB / bronchiectasis / HIV

16. FEVER — "FEVER + TRIPS"

F — Frequency and pattern: continuous / swinging / tertian / quotidian
E — Exact temperature, rigors?
V — Vaccination history
E — Exposure: animal, sick contacts, sexual history
R — Recent antibiotics?

T — Travel: where, when, malaria prophylaxis?
R — Rash: type, distribution, timing relative to fever?
I — Immunosuppression: HIV, steroids, chemotherapy, transplant?
P — Prosthetics: valves, joints, lines, catheters (source of infection)
S — Source localisation: dysuria, cough, headache, neck stiffness, joint pain, abdominal pain?

17. WEIGHT LOSS — "MEND"

M — Magnitude: how much, over what time? (>5% in 6 months = significant)
E — Eating: appetite normal (malabsorption/malignancy) or reduced (depression/malignancy/drugs)?
N — New symptoms: night sweats, fever, lymph nodes (lymphoma)
D — Depression / Diabetes / Drugs (cause of weight loss)

QUICK REFERENCE SUMMARY TABLE

The Universal Add-Ons (Every Complaint)

After every HoPI, always ask:

1. "Have you had this before?"
2. "Did you see a doctor? What did they say?"
3. "Are you worried about anything specific?" (ICE)
4. "Is there anything else you think is important?"

Complete Investigations Guide — By Chief Complaint

Framework for ordering investigations: Always think in tiers: Bedside → Bloods → Imaging → Special Order from least invasive, fastest, cheapest first.

THE UNIVERSAL INVESTIGATION FRAMEWORK

TIER 1 — BEDSIDE (Immediate, no delay)
├── Vital signs (HR, BP both arms, RR, SpO2, Temp, GCS)
├── ECG
├── Urinalysis (dipstick)
├── Blood glucose (fingerprick)
└── Peak flow (if respiratory)

TIER 2 — BLOODS (First-line labs)
├── FBC — Full Blood Count
├── U&E — Urea & Electrolytes (renal function)
├── LFTs — Liver Function Tests
├── CRP / ESR — Inflammation markers
├── Coagulation — PT, APTT, INR
├── Blood glucose / HbA1c
├── TFTs — Thyroid Function
└── Group & Save / Crossmatch (if bleeding/surgical)

TIER 3 — IMAGING (Directed by diagnosis)
├── CXR — Chest X-Ray
├── USS — Ultrasound
├── CT — Computed Tomography
├── MRI
└── Echo / Doppler / Nuclear

TIER 4 — SPECIAL / INVASIVE
├── Biopsy
├── Endoscopy
├── Angiography
├── Lumbar puncture
└── Speciality-specific tests

1. CHEST PAIN

Bedside

• ECG — FIRST within 10 minutes
  - ST elevation → STEMI (Δ in ≥2 contiguous leads)
  - ST depression / T-wave inversion → NSTEMI/UA
  - S1Q3T3 + sinus tachycardia → PE
  - Saddle-shaped ST elevation → Pericarditis
  - Wide mediastinum on CXR → Dissection
  - PR depression → Pericarditis
• SpO2
• BP in BOTH arms (>20 mmHg difference → dissection)

Bloods

• Troponin I or T (high-sensitivity)
  - Rises: 3-6 hrs after MI onset; peaks 12-24 hrs; normalises 7-14 days
  - Serial troponin: 0hr + 3hr (hs-cTn) or 0hr + 6hr (conventional)
  - Elevated also in: PE, myocarditis, sepsis, renal failure, demand ischaemia
• CK-MB (older marker, useful for re-infarction within 24–48 hrs)
• BNP / NT-proBNP
  - Elevated in: heart failure, RV strain (PE), severe ACS
• D-dimer
  - Only useful if pre-test probability is LOW
  - Negative D-dimer + low Wells score → PE excluded
  - NOT useful in high pre-test probability (always elevated)
• ABG (Arterial Blood Gas)
  - PE: hypoxia + hypocapnia + respiratory alkalosis
  - Pneumothorax: hypoxia
• FBC — anaemia (demand ischaemia), leukocytosis (infection/infarction)
• U&E — baseline before contrast/medications
• Lipid profile — cardiovascular risk
• Glucose / HbA1c — DM risk factor
• Coagulation — if anticoagulation planned
• Blood cultures — if fever (endocarditis, sepsis)

Imaging

• CXR (PA erect)
  - Cardiomegaly → heart failure
  - Pulmonary oedema → LVF
  - Wide mediastinum (>8cm) → Dissection
  - Pneumothorax → absent lung markings
  - Consolidation → pneumonia
  - Hampton's hump / Westermark sign → PE
• CTPA (CT Pulmonary Angiogram)
  - Gold standard for PE
• CT Aortogram (with contrast)
  - Gold standard for aortic dissection (sensitivity 98%)
• Echo (Transthoracic or Transoesophageal)
  - Wall motion abnormality → ACS/MI
  - Effusion → pericarditis/tamponade
  - Aortic regurgitation / flap → dissection
  - RV dilation → PE
• Coronary Angiogram (Cardiac Cath)
  - Gold standard for coronary artery disease
  - Allows immediate PCI (angioplasty/stenting)
• V/Q Scan — PE (if contrast contraindicated)
• Stress Testing (only when acute causes excluded)
  - Exercise ECG / Stress echo / Nuclear stress test

Special

• Cardiac MRI — myocarditis, cardiomyopathy, pericarditis
• Pericardiocentesis — if tamponade (diagnostic + therapeutic)
• Pleural aspirate — if effusion (LDH, protein, pH, culture, cytology)

2. DYSPNOEA

Bedside

• SpO2 (pulse oximetry)
• Peak Expiratory Flow Rate (PEFR)
  - <50% predicted → severe asthma attack
• ECG — arrhythmia, RV strain (PE), ischaemia
• Urinalysis — nephrotic syndrome causing oedema

Bloods

• ABG — essential in severe dyspnoea
  TYPE 1 Respiratory Failure: PaO2 <8 kPa, PaCO2 normal/low
  TYPE 2 Respiratory Failure: PaO2 <8 kPa, PaCO2 >6 kPa
  Metabolic acidosis (DKA, sepsis)
  Metabolic alkalosis (over-diuresis)

• FBC
  - Anaemia → reduced O2 carrying capacity
  - Polycythaemia → chronic hypoxia
• BNP / NT-proBNP
  - Elevated → heart failure (very sensitive)
  - BNP <100 → heart failure very unlikely
• D-dimer → PE (low pre-test probability only)
• Troponin → MI causing pulmonary oedema
• U&E — electrolytes, renal function
• TFTs — thyroid (hypo/hyperthyroidism → dyspnoea/palpitations)
• CRP / procalcitonin — infection (pneumonia)
• Sputum culture & sensitivity
• Blood cultures — if fever/sepsis

Imaging

• CXR
  - Bilateral perihilar ("bat-wing") shadowing → pulmonary oedema
  - Consolidation → pneumonia
  - Hyperinflation + flattened diaphragm → COPD/emphysema
  - Pneumothorax
  - Effusion (blunted costophrenic angle)
  - Cardiomegaly
• CT Chest (HRCT)
  - Interstitial lung disease (ILD)
  - Bronchiectasis, emphysema, malignancy
• CTPA → PE (gold standard)
• Echocardiography
  - LV systolic/diastolic function
  - Pulmonary hypertension
• V/Q scan → PE

Special / Pulmonary Function Tests

• Spirometry (Gold standard for obstructive vs restrictive disease)
  FEV1/FVC <0.7 → OBSTRUCTIVE (asthma, COPD)
  FVC ↓, FEV1/FVC normal or ↑ → RESTRICTIVE (fibrosis, neuromuscular)
  Reversibility test: >12% + 200mL improvement after bronchodilator → Asthma

• DLCO (Diffusing capacity of CO)
  Reduced in: emphysema, ILD, pulmonary hypertension, anaemia

• 6-Minute Walk Test — functional exercise capacity
• Bronchoscopy + BAL — ILD, malignancy, haemoptysis
• Sleep study — if nocturnal symptoms / OSA

3. PALPITATIONS

Bedside

• ECG (12-lead) — MOST IMPORTANT
  - Long QTc (>440ms men, >460ms women) → LQTS
  - Short PR + delta wave → WPW
  - AF: irregularly irregular, no P waves
  - SVT: narrow complex tachycardia
  - VT: broad complex tachycardia (DANGEROUS)
  - Heart block: PR prolongation / dropped beats
• BP, SpO2

Bloods

• TFTs — hyperthyroidism (AF, sinus tachycardia)
• FBC — anaemia, infection
• U&E — hypokalaemia, hypomagnesaemia (arrhythmia triggers)
• Calcium, Magnesium — electrolyte arrhythmias
• Blood glucose — hypoglycaemia
• Troponin — if chest pain associated
• Drug levels — digoxin toxicity, theophylline
• Toxicology screen — cocaine, amphetamines
• TFTs — essential

Monitoring / Special

• 24-hour Holter Monitor
  - Captures rhythm over 24 hrs
  - Use if symptoms daily

• 48–72 hour Holter / 7-day patch monitor
  - Infrequent palpitations

• Event (loop) recorder (worn 4 weeks)
  - Infrequent episodic symptoms

• Implantable Loop Recorder (ILR)
  - Subcutaneous, lasts 3 years
  - Use for unexplained syncope / rare episodes

• Exercise ECG
  - Arrhythmia provoked by exertion → WPW, CPVT, LQTS

• Electrophysiology Study (EPS)
  - Maps arrhythmia circuit; gold standard
  - Precedes ablation

• Echocardiogram
  - Structural heart disease underlying arrhythmia
  - HCM, valvular disease, cardiomyopathy

4. HEADACHE

Bedside

• BP — hypertensive emergency?
• Fundoscopy — papilloedema (↑ICP), hypertensive retinopathy
• Temperature — meningitis, encephalitis
• Neurological exam — focal deficit, meningism

Bloods

• FBC — infection, anaemia
• CRP / ESR
  - ESR >50 in elderly with temporal headache → Giant Cell Arteritis (GCA)
• Temporal artery biopsy — gold standard for GCA (do not wait — start steroids first)
• U&E, glucose
• Blood cultures — if meningitis suspected
• Coagulation — if anticoagulation or haemorrhage
• Anti-dsDNA, ANA — if SLE vasculitis suspected

Imaging

• CT Head (non-contrast) — FIRST if:
  - Thunderclap headache (SAH)
  - Focal neurological deficit
  - Papilloedema
  - Immunosuppressed
  - Post-trauma
  - Sensitivity for SAH: 98% within 6 hrs, drops to 90% at 24 hrs

• MRI Brain (better than CT for):
  - Posterior fossa lesions
  - Venous sinus thrombosis (MRI + MRV)
  - Pituitary / sellar pathology
  - Low-pressure headache (meningeal enhancement)

• CT Angiogram / MR Angiogram
  - Intracranial aneurysm, AVM, vasculitis

Special

• Lumbar Puncture (LP)
  - After CT excludes mass lesion / herniation
  - Indications: suspected SAH (CT negative but clinical suspicion high)
    → Xanthochromia (yellow tinge) = SAH until proven otherwise
  - Meningitis: turbid CSF, high WBC, high protein, low glucose
  - Viral encephalitis: lymphocytosis, normal glucose
  - Opening pressure → raised in idiopathic intracranial hypertension (IIH)

• CSF Analysis:
  Condition        | Appearance | WBC         | Protein | Glucose
  Bacterial mening | Turbid     | ↑↑ Neutro   | ↑↑      | ↓↓
  Viral mening     | Clear      | ↑ Lympho    | ↑       | Normal
  TB mening        | Fibrinous  | ↑ Lympho    | ↑↑      | ↓
  SAH              | Bloody/Xan | RBCs        | ↑       | Normal
  IIH              | Clear      | Normal      | Normal  | Normal

5. ABDOMINAL PAIN

Bedside

• Urinalysis — UTI, renal colic (haematuria), pregnancy (hCG)
• Blood glucose — DKA (abdominal pain + ketones)
• ECG — inferior MI can present as epigastric pain
• Temperature, HR, BP — sepsis / peritonitis
• Pregnancy test (urine β-hCG) in ALL women of reproductive age

Bloods

• FBC
  - WBC ↑ → infection, appendicitis, cholecystitis, bowel ischaemia
  - Anaemia → GI bleeding, malignancy
• CRP / ESR — inflammation, infection
• U&E — electrolytes, renal function (vomiting, diarrhoea)
• LFTs + GGT
  - Raised bilirubin + ALP → obstructive jaundice (gallstones, cholangitis)
  - Raised ALT/AST → hepatitis, ischaemia
• Amylase / Lipase
  - Amylase >3× normal → pancreatitis (sensitivity ~80%)
  - Lipase more sensitive and specific than amylase
• Lactate
  - Elevated → bowel ischaemia, sepsis (EMERGENCY)
• Coagulation — liver disease, DIC
• Blood cultures — if sepsis
• Urine culture — UTI / pyelonephritis
• Serum β-hCG — ectopic pregnancy
• CA-125 — ovarian malignancy (if relevant)
• Hepatitis serology (A, B, C, E) — if hepatitis suspected
• Lipid profile — in pancreatitis (hypertriglyceridaemia as cause)

Imaging

• AXR (Abdominal X-Ray) — limited use, but check for:
  - Bowel obstruction: dilated loops, air-fluid levels
  - Perforation: (Erect CXR better — subdiaphragmatic free air)
  - Calcification: renal stones, gallstones, aortic calcification

• USS Abdomen — FIRST for:
  - Gallstones, cholecystitis (wall thickening, pericholecystic fluid)
  - Bile duct dilatation
  - AAA
  - Appendix (in children/thin patients)
  - Renal stones, hydronephrosis
  - Pelvic organs (transvaginal USS for ectopic)

• CT Abdomen/Pelvis (with contrast)
  - Gold standard for most acute abdominal conditions
  - Appendicitis, diverticulitis, malignancy, pancreatitis staging
  - Bowel obstruction, ischaemia, AAA
  - CT KUB (non-contrast) → renal stones

• Erect CXR
  - Free air under diaphragm → perforation (EMERGENCY)

• MRI Abdomen
  - Liver lesions, bile duct (MRCP), rectal cancer staging

• MRCP (Magnetic Resonance Cholangiopancreatography)
  - Non-invasive biliary/pancreatic duct imaging

• ERCP (Endoscopic Retrograde Cholangiopancreatography)
  - Diagnostic + therapeutic: bile duct stones, strictures

6. JAUNDICE

Bloods

• LFTs (pattern analysis):

  Pattern              | Likely Cause
  ─────────────────────────────────────────────
  ↑↑ ALT/AST          | Hepatocellular damage (hepatitis, ischaemia)
  ↑↑ ALP + GGT        | Cholestatic / obstructive
  ↑ Bilirubin only    | Haemolysis / Gilbert's
  ↑↑ All              | Severe liver disease

• Bilirubin fractionation
  - Unconjugated (indirect) ↑ → pre-hepatic (haemolysis)
  - Conjugated (direct) ↑ → hepatic or post-hepatic (obstruction)

• Albumin ↓ + PT ↑ → synthetic liver function impaired → severe liver disease

• Hepatitis serology
  - HAV IgM → Hep A (acute)
  - HBsAg, HBeAg, HBcAb IgM → Hep B (active infection)
  - Anti-HCV → Hep C
  - HEV IgM → Hep E

• Autoimmune panel
  - Anti-smooth muscle Ab → Autoimmune hepatitis
  - Anti-mitochondrial Ab (AMA) → Primary Biliary Cholangitis (PBC)
  - Anti-LKM1 → AIH type 2
  - ANCA → PSC

• Haemolysis screen
  - Blood film + reticulocytes + haptoglobin ↓ + LDH ↑ + Coombs test

• Ferritin + iron studies → Haemochromatosis
• Caeruloplasmin / 24hr urine copper → Wilson's disease (young patient)
• Alpha-1-antitrypsin level
• Tumour markers: AFP (hepatocellular carcinoma), CA 19-9 (pancreatic/biliary)
• Coagulation (PT/INR) — prognostic marker

Imaging

• USS Liver/Biliary → First line
• MRCP → Biliary duct pathology
• CT Abdomen → Malignancy staging
• Liver biopsy → Definitive diagnosis (grading and staging)

7. ANAEMIA

FBC Interpretation

MCV < 80 (Microcytic)       → Iron deficiency, thalassaemia, sideroblastic anaemia
MCV 80–100 (Normocytic)     → Haemolysis, chronic disease, acute blood loss, renal disease
MCV > 100 (Macrocytic)      → B12/folate deficiency, alcohol, hypothyroidism, drugs

Bloods

• FBC + Reticulocyte count
  - Reticulocytes ↑ → active blood loss or haemolysis (bone marrow responding)
  - Reticulocytes ↓ → bone marrow failure, aplasia, B12/folate deficiency

• Iron studies (Microcytic)
  - Serum iron ↓, TIBC ↑, Ferritin ↓ → Iron deficiency anaemia
  - Serum iron ↓, TIBC ↓, Ferritin ↑ → Anaemia of chronic disease

• B12 and Folate (Macrocytic)
• Haemolysis screen
  - LDH ↑, Haptoglobin ↓, Indirect bilirubin ↑
  - Blood film: schistocytes (MAHA), spherocytes (hereditary/AIHA)
  - Direct Coombs test (DAT) → AIHA

• Haemoglobin electrophoresis → Thalassaemia, Sickle cell
• Blood film — morphology (target cells, sickling, hypersegmented neutrophils)
• Bone marrow biopsy — aplastic anaemia, leukaemia, MDS
• Intrinsic factor antibodies → Pernicious anaemia
• Renal function → EPO deficiency (CKD)
• TFTs → Hypothyroidism
• Coagulation → Bleeding disorder

8. URINARY SYMPTOMS / HAEMATURIA

Bedside

• Urinalysis dipstick
  - Leucocytes + Nitrites → UTI
  - Blood → haematuria (microscopic)
  - Protein → glomerulonephritis, nephrotic syndrome
  - Glucose → DM
  - Ketones → DKA, starvation

Bloods

• FBC — anaemia, infection
• U&E + Creatinine — renal function (AKI/CKD)
• eGFR
• PSA (Prostate Specific Antigen) — prostate cancer (men >40 with LUTS)
• Glucose / HbA1c
• Urine ACR (albumin:creatinine ratio) — proteinuria, CKD monitoring
• Renal/vasculitis screen (if glomerulonephritis suspected):
  - ANA, ANCA, anti-GBM (Goodpasture's), complement C3/C4
  - Anti-streptolysin O (ASOT) — post-streptococcal GN

Urine Tests

• Urine MC&S (Microscopy, Culture, Sensitivity) — UTI
• Urine cytology — transitional cell carcinoma (bladder cancer)
• 24hr urine protein — nephrotic syndrome
• Urine protein electrophoresis — Bence-Jones proteins (myeloma)
• Early morning urine (EMU) × 3 — TB

Imaging

• USS KUB — renal stones, hydronephrosis, masses
• CT KUB (non-contrast) — gold standard for renal stones
• CT Urogram — haematuria workup (malignancy exclusion)
• Cystoscopy — gold standard for bladder cancer diagnosis
• MCUG (Micturating Cystourethrogram) — VUR in children
• Renal biopsy — glomerulonephritis, nephrotic syndrome

9. JOINT PAIN / ARTHRITIS

Bloods

• FBC — anaemia of chronic disease (RA), infection
• CRP + ESR — inflammation severity
• Uric acid — GOUT (but can be normal during acute attack)
• Rheumatoid Factor (RF) — positive in 70–80% RA (also SLE, Sjögren's)
• Anti-CCP (Anti-citrullinated peptide antibodies)
  - More specific for RA (95% specificity); positive before symptoms
• ANA (Antinuclear Antibodies) — SLE, autoimmune disease
• Anti-dsDNA — specific for SLE
• HLA-B27 — Ankylosing spondylitis, reactive arthritis, psoriatic arthritis
• Complement C3/C4 ↓ — active SLE
• ASO titre — reactive arthritis post-strep
• Blood cultures — septic arthritis
• TFTs — hypothyroid myopathy
• Creatine Kinase (CK) — myositis, polymyositis
• Calcium, phosphate, PTH, Vit D → metabolic bone disease

Synovial Fluid Analysis

JOINT ASPIRATION — CRITICAL FOR:
  - Septic arthritis (EMERGENCY — do before antibiotics)
  - Crystal arthropathy (gout vs pseudogout)

Test           | Normal    | Non-inflamatory | Inflammatory | Septic
Appearance     | Clear     | Clear/yellow    | Cloudy       | Turbid/purulent
WBC/mm³        | <200      | <2000           | 2000–50000   | >50000
Neutrophils    | <25%      | <25%            | >50%         | >75%
Culture        | Negative  | Negative        | Negative     | Positive
Crystals       | None      | None            | Urate/CPPD   | None

Crystals:
  Urate (Gout): Needle-shaped, NEGATIVELY birefringent (yellow parallel to light)
  CPPD (Pseudogout): Rhomboid, POSITIVELY birefringent (blue parallel to light)

Imaging

• X-Ray of affected joints
  - RA: periarticular osteoporosis, joint space narrowing, erosions, subluxation
  - OA: joint space narrowing, osteophytes, subchondral sclerosis, cysts
  - Gout: "punched out" erosions with overhanging edge
  - AS: sacroiliitis, "bamboo spine"

• MRI — soft tissue, early erosions, sacroiliitis, enthesitis
• USS — joint effusion, synovitis, guided aspiration
• Bone scan (scintigraphy) — polyarthritis, metastases
• DEXA scan — bone density, osteoporosis

10. FEVER / SEPSIS

Bedside

• Blood cultures (×2 sets from different sites) BEFORE antibiotics
• ECG — sepsis-induced arrhythmia
• Urinalysis + urine MC&S
• Lactate (point-of-care) — >2 mmol/L = sepsis; >4 = septic shock

Bloods

• FBC
  - WBC ↑ → bacterial infection
  - WBC ↓ → viral, overwhelming sepsis, bone marrow failure
  - Left shift (band neutrophils) → bacterial infection

• CRP → general inflammation
• Procalcitonin (PCT)
  - Highly specific for BACTERIAL infection
  - PCT >0.5 → bacterial; >2 → severe sepsis
  - Useful for antibiotic stewardship (guide stopping antibiotics)

• ESR — chronic infection, malignancy
• Blood cultures × 2
• LFTs — liver involvement, drug reaction
• U&E — dehydration, AKI
• Lactate — tissue perfusion
• Coagulation — DIC (sepsis complication)
• Thick and thin blood film → Malaria (if travel)
• Malaria RDT (rapid diagnostic test)
• Monospot / EBV / CMV serology — if young + lymphadenopathy
• HIV test — if risk factors
• Serology: brucella, legionella, rickettsia, leptospira (travel history)
• Urine Legionella antigen + Pneumococcal antigen
• TB: Mantoux, IGRA (Interferon Gamma Release Assay), Sputum AFB × 3
• Cultures: sputum, urine, wound swabs, CSF if meningitis suspected

Imaging

• CXR — pneumonia, effusion, TB
• USS — intra-abdominal abscess, biliary sepsis
• CT Chest/Abdomen/Pelvis — occult sepsis source
• Echocardiogram — infective endocarditis (TTE then TOE)
• Bone scan / MRI — osteomyelitis, discitis
• PET-CT — fever of unknown origin (FUO)

11. NEUROLOGICAL (Weakness / Altered Consciousness)

Bedside

• GCS (Glasgow Coma Scale)
• Blood glucose — hypoglycaemia (first reversible cause to exclude)
• ECG — arrhythmia causing reduced perfusion
• Temperature — meningitis, encephalitis

Bloods

• Blood glucose — hypoglycaemia
• FBC, U&E — metabolic encephalopathy
• Calcium — hypo/hypercalcaemia (seizures, confusion)
• Sodium — hypo/hypernatraemia (seizures, confusion)
• LFTs + Ammonia → hepatic encephalopathy
• TFTs — myxoedema coma, thyroid storm
• B12, Folate → subacute combined degeneration
• Syphilis serology (VDRL/TPHA) — neurosyphilis
• HIV
• Thiamine — Wernicke's encephalopathy (alcoholics)
• Autoimmune encephalitis panel: Anti-NMDAR, anti-LGI1, anti-CASPR2
• Paraneoplastic panel: anti-Hu, anti-Yo, anti-Ri
• Cortisol — Addisonian crisis
• Toxicology screen
• Blood cultures — meningitis, encephalitis
• Coagulation — intracranial haemorrhage risk

Imaging

• CT Head (non-contrast) — URGENT first line
  - Exclude haemorrhage before LP
  - Infarct (may be normal in first 6 hrs)
  - Mass lesion, midline shift

• MRI Brain — SUPERIOR for:
  - Ischaemic stroke (DWI sequence — positive within minutes)
  - Posterior fossa lesions
  - MS plaques (periventricular, FLAIR)
  - Encephalitis
  - Dementia

• MRA / CTA — vascular (aneurysm, AVM, carotid stenosis)
• EEG — seizures, encephalitis, non-convulsive status
• LP (after CT) — meningitis, encephalitis, SAH, MS (oligoclonal bands)
• EMG / Nerve Conduction Studies — peripheral neuropathy, myopathy
• Carotid Doppler USS — carotid stenosis (TIA/stroke workup)

QUICK REFERENCE: INVESTIGATIONS BY COMPLAINT

COMPLAINT          MUST-DO FIRST          GOLD STANDARD
─────────────────────────────────────────────────────────
Chest pain         ECG + Troponin         Coronary angiogram
Dyspnoea           ABG + CXR              Spirometry / CTPA
Palpitations       12-lead ECG            24hr Holter / EPS
Headache           CT head                LP (if CT negative, SAH suspected)
Abdominal pain     USS + β-hCG            CT Abdomen/Pelvis
Jaundice           LFTs + USS             Liver biopsy / MRCP
Anaemia            FBC + Blood film       Bone marrow biopsy
Haematuria         Urine MC&S + USS       Cystoscopy + CT Urogram
Joint pain         CRP + X-Ray            Synovial fluid aspiration
Fever              Blood cultures + FBC   Culture + PET-CT (FUO)
Neurology          BM + CT head           MRI Brain + LP
─────────────────────────────────────────────────────────

THE INVESTIGATION ORDERING PRINCIPLE

Ask 3 questions before ordering any test:

1. WILL IT CHANGE MANAGEMENT?
   If the result won't change what you do → don't order it

2. IS THE PATIENT HIGH OR LOW PRE-TEST PROBABILITY?
   Low probability + sensitive test = rule OUT
   High probability + specific test = rule IN

3. LEAST INVASIVE FIRST
   Bedside → Bloods → Imaging → Invasive → Biopsy