USMLE High Yield
🧠 High-Yield USMLE Medicine Facts are best learned as pattern-recognition triggers rather than isolated facts.
⚡ On exam day, the key is to link a classic vignette to the single most likely diagnosis, investigation, or next best step.
👉 Focus on red flags, discriminators, and “can’t miss” management decisions.
🚨 Rapid-Fire “Next Best Step” Triggers
- ⚡ Unstable tachyarrhythmia → synchronized cardioversion
- ⚡ Pulseless VT/VF → defibrillation
- ⚡ Tension pneumothorax → immediate decompression
- ⚡ Cardiac tamponade → urgent pericardiocentesis
- ⚡ TTP → plasma exchange
- ⚡ Temporal arteritis with visual symptoms → immediate steroids
- ⚡ Suspected meningococcal sepsis/meningitis → urgent antibiotics
- ⚡ Ascending cholangitis → antibiotics + biliary decompression
- ⚡ DKA → IV fluids first, then insulin and potassium-guided replacement
- ⚡ Hyperkalaemia with ECG changes → IV calcium first
🧠 USMLE Exam Tips
- 📌 Read the last line first: diagnosis, investigation, mechanism, or management?
- 📌 Look for the discriminator in the stem: pain pattern, rash, electrolyte clue, murmur manoeuvre, ECG pattern.
- 📌 In emergencies, the answer is often the stabilising step, not the definitive diagnosis test.
- 📌 If two diagnoses seem close, choose the one best supported by the single classic clue.
- 📌 Repeated testing often focuses on common dangerous misses: PE, MI, dissection, meningitis, temporal arteritis, ectopic pregnancy, DKA, hyperkalaemia.
🩸 Anaemia Classification (Core Exam Table)
| Type | MCV | Causes | Key Clue |
|---|
| Microcytic | ↓ | Iron deficiency, thalassaemia, chronic disease | Low ferritin (iron deficiency) |
| Normocytic | Normal | Acute blood loss, haemolysis | ↑ reticulocytes |
| Macrocytic | ↑ | B12, folate, alcohol | Neurological signs → B12 |
🧠 Acid–Base Disorders
| Disorder | Primary Problem | Example | Key Tip |
|---|
| Metabolic acidosis | ↓ HCO₃⁻ | DKA, renal failure | Check anion gap |
| Metabolic alkalosis | ↑ HCO₃⁻ | Vomiting, diuretics | Often volume depletion |
| Respiratory acidosis | ↑ CO₂ | COPD | Hypoventilation |
| Respiratory alkalosis | ↓ CO₂ | Anxiety | Hyperventilation |
🧪 Thyroid Function Patterns
| Condition | TSH | T4 | Cause |
|---|
| Primary hypothyroid | ↑ | ↓ | Thyroid failure |
| Primary hyperthyroid | ↓ | ↑ | Graves |
| Secondary hypothyroid | ↓ | ↓ | Pituitary |
⚡ Electrolyte Patterns
| Electrolyte | High | Low | Key Danger |
|---|
| Potassium | Renal failure, ACEi | Diuretics, vomiting | Arrhythmias |
| Sodium | Dehydration | SIADH | Brain oedema |
| Calcium | Malignancy, hyperPTH | Hypoparathyroid | Seizures |
🦠 Meningitis Organisms by Age
| Age Group | Common Organisms |
|---|
| Neonates | Group B Strep, E. coli, Listeria |
| Adults | Strep pneumoniae, Neisseria meningitidis |
| Elderly | + Listeria |
❤️ Chest Pain Differentials
| Condition | Pain Type | Key Feature |
|---|
| MI | Crushing | Radiates to arm/jaw |
| Pericarditis | Pleuritic | Better sitting forward |
| Aortic dissection | Tearing | Back radiation |
| PE | Pleuritic | Dyspnoea |
🧬 Nephritic vs Nephrotic
| Feature | Nephritic | Nephrotic |
|---|
| Protein | Mild | Heavy (>3.5g) |
| Blood | Yes | No |
| Oedema | Mild | Severe |
| Mechanism | Inflammation | Permeability |
🦴 Inflammatory vs Non-inflammatory Arthritis
| Feature | Inflammatory | Non-inflammatory |
|---|
| Morning stiffness | >30–60 min | <30 min |
| Swelling | Yes | Minimal |
| Examples | RA, SLE | Osteoarthritis |
🫀 Shock Types
| Type | Cause | CO | SVR | Key Clue |
|---|
| Hypovolaemic | Blood/fluid loss | ↓ | ↑ | Cold, tachycardic |
| Cardiogenic | MI, HF | ↓ | ↑ | Pulmonary oedema |
| Distributive | Sepsis, anaphylaxis | ↑ | ↓ | Warm peripheries (early) |
| Obstructive | PE, tamponade | ↓ | ↑ | JVP ↑ |
🫁 Hypoxia Causes (A–a Gradient)
| Cause | A–a Gradient | Example |
|---|
| Hypoventilation | Normal | Opioids |
| V/Q mismatch | ↑ | PE, pneumonia |
| Shunt | ↑ | ARDS |
| Diffusion defect | ↑ | Fibrosis |
🧠 Cranial Nerve Lesions
| Nerve | Function | Lesion |
|---|
| III | Eye movement | Down & out eye |
| VII | Facial movement | Facial droop |
| IX/X | Swallowing | Dysphagia |
| XII | Tongue | Deviation to side |
🩺 Heart Murmurs
| Murmur | Timing | Key Feature |
|---|
| Aortic stenosis | Systolic | Radiates to carotids |
| Mitral regurgitation | Systolic | Radiates to axilla |
| Aortic regurgitation | Diastolic | Wide pulse pressure |
| Mitral stenosis | Diastolic | Opening snap |
🧬 Tumour Markers
| Marker | Cancer |
|---|
| AFP | Hepatocellular, germ cell |
| CEA | Colorectal |
| CA-125 | Ovarian |
| PSA | Prostate |
🦠 Antibiotic Coverage (Core)
| Drug | Covers | Key Note |
|---|
| Penicillin | Gram+ | Strep |
| Vancomycin | Gram+ | MRSA |
| Ceftriaxone | Broad | Meningitis |
| Piperacillin-tazobactam | Broad incl Pseudomonas | Sepsis |
🧪 Liver Patterns
| Pattern | Labs | Cause |
|---|
| Hepatocellular | ↑ AST/ALT | Hepatitis |
| Cholestatic | ↑ ALP | Obstruction |
🧠 Dementia Types
| Type | Feature |
|---|
| Alzheimer | Memory loss first |
| Vascular | Stepwise decline |
| Lewy body | Visual hallucinations |
| Frontotemporal | Personality change |
🧂 Fluid Status Clues
| State | Signs |
|---|
| Hypovolaemia | Tachycardia, dry mucosa |
| Hypervolaemia | Oedema, JVP ↑ |
🦠 Rash + Fever Differentials
| Condition | Rash | Clue |
|---|
| Meningococcaemia | Petechial | Sepsis |
| Measles | Maculopapular | Koplik spots |
| Scarlet fever | Sandpaper | Strawberry tongue |
| Chickenpox | Vesicular | Different stages |
