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USMLE Step 3 Cheat Sheet

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Biostatistics & Epidemiology

  • 11-13% of exam
  • Sensitivity/Specificity NNT/NNH Study Design Bias & Confounding

Ethics, Legal & Patient Safety

  • 7-9% of exam
  • Capacity & Consent Minor Consent Patient Safety Root Cause Analysis

Pharmacology & Foundational Science

  • Not published of exam
  • Reversal Agents Drug Interactions Pharmacokinetics CYP450

CCS Case Simulation Strategy

  • Not published of exam
  • Order Entry Clock Management Follow-up Orders Scoring Domains

Cardiovascular System

  • 9-11% of exam
  • ACS/ECG Hypertension Atrial Fibrillation Murmurs

Pulmonary & Critical Care

  • 8-10% of exam
  • CURB-65 Wells/PERC ARDS Berlin COPD Exacerbation

Gastrointestinal System

  • 6-8% of exam
  • GI Bleed Timing Hepatic Encephalopathy Pancreatitis Ascites

Renal & Urinary System

  • 4-6% of exam
  • Anion Gap Hyponatremia DKA Electrolytes Acid-Base

Infectious Disease & Heme/Onc

  • 6-8% of exam
  • Sepsis-3/qSOFA Febrile Neutropenia Anemia Workup Virchow's Triad

Endocrine System

  • 5-7% of exam
  • Diabetes Management Thyroid Labs DKA vs HHS A1c Goals

Neurology & Special Senses

  • 8-10% of exam
  • Stroke tPA Window Subarachnoid Hemorrhage NPH Triad Botulism

Psychiatry & Behavioral Health

  • 4-6% of exam
  • Serotonin Syndrome NMS Benzo Withdrawal Alcohol Withdrawal

OB/GYN & Reproductive Health

  • 7-9% of exam
  • Preeclampsia Ectopic Pregnancy Pregnancy UTI hCG Trends

Pediatrics & Preventive Care

  • 1-3% of exam
  • Vaccine Schedule Growth & Development Lead Screening Well-Child Care

Musculoskeletal System

  • 5-7% of exam
  • Gout vs Pseudogout Septic Arthritis Arthrocentesis Crystal Analysis

Dermatology

  • 4-6% of exam
  • SJS/TEN Melanoma ABCDE Drug Eruptions BSA Staging

Quick Facts

  • Exam USMLE Step 3
  • Body FSMB / NBME
  • Format 2-day: FIP, ACM, CCS
  • MCQs 412 (232 Day1 + 180 Day2)
  • CCS Cases 13-14, Day 2 only
  • Time ~16h total (7h + 9h)
  • Pass Score 200 (3-digit scale)
  • Pass Rate 96% MD / 97% DO
  • Level Final USMLE licensing step
  • Fee $955 (2026)

SnNout and SpPin Test Rules BI

  • High sensitivity rules out; high specificity rules in
  • SnNout: sensitive, negative, out SpPin: specific, positive, in

RCT/Cohort vs Case-Control BI

RCT/cohort

  • Report relative risk
  • Exposure forward

Case-control

  • Report odds ratio
  • Outcome backward
  • Design dictates measure

Test Statistics & Predictive Value BI

  • Sensitivity TP/(TP+FN); SnNout
  • Specificity TN/(TN+FP); SpPin
  • PPV TP/(TP+FP), prevalence-dependent
  • NPV TN/(TN+FN), prevalence-dependent
  • NNT 1/ARR, lower is better
  • NNH 1/ARI, lower is worse
  • Relative risk Cohort/RCT studies only
  • Odds ratio Case-control studies only

Study Design & Bias BI

  • Confounder Linked to exposure and outcome
  • Effect modifier Different effect by subgroup
  • Type I error Alpha, false positive
  • Type II error Beta, false negative
  • Power 1-beta, detects true effect
  • RCT Gold standard for causation
  • Cohort study Exposure forward to outcome
  • Case-control Outcome backward to exposure

Capacity, Consent & Confidentiality ET

  • Capacity Communicate, understand, appreciate, reason
  • Autonomy Refusal trumps beneficence
  • Minor consent Emergency, STI, emancipated minor
  • Surrogate order Spouse, adult child, parent
  • Confidentiality break Duty to warn/protect
  • Advance directive Overrides family wishes

Patient Safety & Systems ET

  • Swiss cheese model System fault, not individual
  • Root cause analysis Retrospective systems review
  • Sentinel event Unexpected death or serious harm
  • Near miss Error caught before harm
  • PDSA cycle Plan-Do-Study-Act quality improvement

Dabigatran vs Factor Xa Reversal PH

Dabigatran

  • Idarucizumab reverses
  • Direct thrombin inhibitor

Factor Xa inhibitors

  • Andexanet alfa reverses
  • Apixaban, rivaroxaban
  • Match antidote to target

Anticoagulant Reversal Selection PH

  • Dabigatran bleeding → Idarucizumab
  • Factor Xa inhibitor bleeding → Andexanet alfa
  • Warfarin, life-threatening bleed → 4-factor PCC + vitamin K
  • Heparin overdose/bleeding → Protamine sulfate

Antidotes & Reversal Agents PH

  • Dabigatran Idarucizumab reverses
  • Factor Xa inhibitors Andexanet alfa reverses
  • Warfarin (urgent) 4-factor PCC + vitamin K
  • Heparin Protamine sulfate reverses
  • Opioids Naloxone reverses
  • Benzodiazepines Flumazenil (caution: seizures)
  • Acetaminophen N-acetylcysteine reverses
  • Beta-blocker overdose Glucagon reverses

Drug Interactions & Mechanisms PH

  • CYP3A4 inhibitor + statin Raises myopathy risk
  • Protein-binding displacement Raises free-drug fraction
  • ACE inhibitor cough Bradykinin buildup; switch ARB
  • Warfarin necrosis Protein C depletes first
  • Serotonin syndrome trigger SSRI plus MAOI/tramadol

CCS Order Entry & Timing CC

  • Order entry Free-text, pick autocomplete
  • Clock advance Move to next needed time
  • Follow-up orders Schedule reassessment, not just treat
  • Case length 10-20 simulated minutes
  • Location changes Move to ICU when unstable
  • Scoring domains Diagnosis, therapy, timing, sequencing

HCM vs Aortic Stenosis Murmur CA

HCM

  • Louder with Valsalva
  • Softer with squatting

Aortic stenosis

  • Softer with Valsalva
  • Louder with squatting
  • Preload response is opposite

Acute Chest Pain Pathway CA

  • ST elevation present → Emergent reperfusion ( PCI <90 min preferred )
  • ST depression V1-V3 → Suspect posterior MI ( Confirm posterior leads )
  • Troponin positive, no ST changes → NSTEMI pathway ( Anticoagulate + risk stratify )
  • Low-risk, normal troponin → Outpatient stress test ( If reassuring exam )

Coronary & ECG Patterns CA

  • Posterior MI ST depression, tall R, V1-3
  • STEMI door-to-balloon 90 minute goal
  • STEMI door-to-needle 30 minute goal (lytics)
  • NSTEMI/UA Troponin up, no ST elevation
  • CABG preferred 3-vessel or left main disease

AF Anticoagulation Decision CA

  • CHA2DS2-VASc ≥2, men → Anticoagulate
  • CHA2DS2-VASc ≥3, women → Anticoagulate
  • Valvular AF (mechanical valve) → Warfarin only ( Not DOAC )
  • Low score, no other RF → Consider no anticoagulation

Hypertension & Arrhythmia Targets CA

  • BP goal <130/80 most adults (ACC/AHA)
  • Stage 2 HTN ≥140/90 mmHg
  • CHA2DS2-VASc ≥2 Anticoagulate (men)
  • CHA2DS2-VASc ≥3 Anticoagulate (women)
  • DOAC preferred Over warfarin, nonvalvular AF
  • HCM murmur Louder Valsalva, softer squat
  • AS murmur Softer Valsalva, louder squat

CURB-65 Pneumonia Severity Score PU

  • Confusion, Urea, Respiratory rate, Blood pressure, Age 65
  • Confusion Urea >19 RR ≥30 BP <90/60 Age ≥65

Suspected PE Workup PU

  • Low Wells score → Order D-dimer
  • D-dimer negative → PE excluded
  • Moderate/high Wells → CT pulmonary angiography ( Skip D-dimer )
  • PERC all negative → No further testing

Pulmonary Risk Scores PU

  • CURB-65 ≥2 Admit for CAP
  • CURB-65 ≥3 Consider ICU care
  • Wells low + neg D-dimer PE effectively excluded
  • Wells moderate/high CT-PA, skip D-dimer
  • PERC all negative No further PE workup
  • Berlin ARDS PaO2/FiO2 ≤300, bilateral opacities
  • ARDS severity Mild 200-300, severe ≤100

COPD & Asthma Management PU

  • COPD exacerbation triad Bronchodilator, steroid, antibiotic
  • Antibiotic trigger Purulent sputum or vent need
  • Home O2 criteria PaO2 ≤55 or SpO2 ≤88%
  • Status asthmaticus Silent chest, no air movement

GI Bleeding & Liver Disease GA

  • Upper GI bleed scope Within 24h, after resuscitation
  • Hepatic encephalopathy Lactulose is first-line
  • Refractory HE Add rifaximin
  • Pancreatitis diagnosis 2 of 3 criteria met
  • Lipase threshold >3x upper limit normal
  • SAAG ≥1.1 Portal hypertension cause

High Anion Gap Causes (MUDPILES) RE

  • Methanol, Uremia, DKA, Paraldehyde, Iron-INH, Lactic, Ethylene-glycol, Salicylates
  • Methanol Uremia DKA Paraldehyde Iron/INH Lactic acidosis Ethylene glycol Salicylates

Electrolytes & Acid-Base RE

  • Anion gap Na−Cl−HCO3, normal 8-12
  • MUDPILES High anion gap causes
  • Hyponatremia correction ≤8 mEq/L per 24h
  • Overcorrection risk Osmotic demyelination syndrome
  • DKA potassium rule Replete K+ before insulin
  • DKA insulin hold Hold if K+ below 3.3

Virchow's Triad for Thrombosis ID

  • Stasis, endothelial injury, and hypercoagulability cause clots
  • Stasis: immobility Injury: vessel wall damage Hypercoagulability: clotting factors

Iron Deficiency vs Thalassemia Trait ID

Iron deficiency

  • High RDW
  • Low ferritin

Thalassemia trait

  • Normal RDW
  • Low Mentzer index
  • RDW variability is key

Sepsis & Infection Thresholds ID

  • qSOFA ≥2 RR≥22, altered mentation, SBP≤100
  • Sepsis-3 Infection plus organ dysfunction
  • Septic shock Lactate>2 plus pressors needed
  • Febrile neutropenia Antibiotics within 1 hour
  • Empiric agent Cefepime or pip-tazo

qSOFA Sepsis Screening Criteria ID

  • Respiratory rate, altered mentation, and low systolic BP
  • RR ≥22/min Altered mentation SBP ≤100 mmHg

Hematology & Oncology ID

  • Iron deficiency High RDW, low ferritin
  • Thalassemia trait Normal RDW, low Mentzer
  • Mentzer index MCV/RBC <13, thalassemia
  • Virchow's triad Stasis, injury, hypercoagulability

Subclinical vs Overt Hypothyroidism EN

Subclinical

  • High TSH
  • Normal free T4

Overt

  • High TSH
  • Low free T4
  • Free T4 makes diagnosis

DKA Fluid-Insulin-Potassium Sequence EN

  • K+ below 3.3 → Hold insulin, replete K+
  • K+ 3.3-5.3 → Start insulin + K+ together
  • K+ above 5.3 → Start insulin, monitor K+
  • Glucose reaches ~200 → Add dextrose, continue insulin

Thyroid & Diabetes Management EN

  • Metformin First-line for T2DM
  • Subclinical hypothyroid High TSH, normal free T4
  • Overt hypothyroid High TSH, low free T4
  • DKA vs HHS Ketoacidosis vs extreme glucose
  • A1c goal <7% most adults

Normal Pressure Hydrocephalus Triad NE

  • Wet, wobbly, and wacky — incontinence, gait, cognition
  • Wet: incontinence Wobbly: gait apraxia Wacky: dementia

Acute Ischemic Stroke Pathway NE

  • Within 4.5h, CT clear → Give IV tPA ( If BP <185/110 )
  • BP too high → Lower before tPA ( Labetalol/nicardipine )
  • Large vessel occlusion → Add mechanical thrombectomy ( Up to 24h select cases )
  • Beyond window/contraindicated → Antiplatelet + supportive care

Stroke & Neuro Emergencies NE

  • tPA window 4.5h from last known well
  • tPA BP limit <185/110 mmHg
  • Worst headache ever CT then LP for SAH
  • CT sensitivity drop After 6-12h for SAH
  • NPH triad Wet, wobbly, and wacky
  • NPH first response Gait improves first
  • Botulism Descending paralysis, antitoxin

Serotonin Syndrome vs NMS PS

Serotonin syndrome

  • Hyperreflexia, clonus
  • Rapid onset (hours)

NMS

  • Lead-pipe rigidity
  • Slow onset (days)
  • Reflexes up vs rigid

Psychiatric Emergencies PS

  • Serotonin syndrome Hyperreflexia, clonus, rapid onset
  • NMS Lead-pipe rigidity, slow onset
  • Benzo withdrawal Seizure risk; taper, don't stop
  • Alcohol withdrawal Peaks 24-72h, DTs risk

OB Emergencies & Pregnancy Risk OB

  • Preeclampsia, severe BP ≥160/110 plus symptoms
  • Eclampsia prophylaxis Magnesium sulfate is first-line
  • hCG rise rule ≥53% in 48h is normal
  • Suboptimal hCG rise Rule out ectopic pregnancy
  • UTI in pregnancy Avoid fluoroquinolones
  • Near-term UTI Avoid nitrofurantoin, sulfa

Pediatric & Preventive Care PE

  • MMR dose 1 12-15 months
  • MMR dose 2 4-6 years
  • MMR contraindication Pregnancy, immunosuppression
  • Lead screening 12 and 24 months

Gout vs Pseudogout Crystals MS

Gout

  • Negative birefringence
  • Needle-shaped

Pseudogout

  • Positive birefringence
  • Rhomboid-shaped
  • Birefringence sign flips

Joint & Crystal Disease MS

  • Gout crystals Negative birefringent, needle-shaped
  • Pseudogout crystals Positive birefringent, rhomboid
  • Septic arthritis Arthrocentesis before antibiotics
  • Septic WBC threshold >50,000/µL, PMN predominant

SJS vs TEN DE

SJS

  • <10% BSA sloughing
  • Better prognosis

TEN

  • >30% BSA sloughing
  • Higher mortality
  • BSA percentage decides severity

Dermatologic Emergencies DE

  • SJS <10% BSA sloughing
  • SJS/TEN overlap 10-30% BSA sloughing
  • TEN >30% BSA sloughing
  • SJS/TEN first step Stop the offending drug
  • ABCDE melanoma Asymmetry, border, color, diameter, evolving

Common Traps

Sensitivity ≠ specificity direction

  • Sensitivity rules out disease ≠ Specificity rules in disease

Relative risk ≠ odds ratio

  • RR needs cohort/RCT design ≠ OR needs case-control design

System error ≠ individual blame

  • Latent system defect at fault ≠ Fix the process, not person

CURB-65 ≠ qSOFA

  • CURB-65 is pneumonia-specific ≠ qSOFA is general sepsis screen

Idarucizumab ≠ andexanet alfa

  • Idarucizumab reverses dabigatran only ≠ Andexanet alfa reverses factor Xa

Subclinical ≠ overt hypothyroidism

  • Subclinical has normal free T4 ≠ Overt has low free T4

SJS ≠ TEN severity

  • SJS is under 10% BSA ≠ TEN is over 30% BSA

Hyponatremia correction ≠ unlimited

  • Max 8 mEq/L per 24h ≠ Faster risks brain demyelination

Last Minute

  • 1. 412 MCQs: 232 Day1, 180 Day2
  • 2. 13-14 CCS cases, Day 2 only
  • 3. Pass score is 200, 3-digit
  • 4. CCS: free-text order entry, autocomplete
  • 5. Schedule follow-up orders in CCS
  • 6. BP goal <130/80 most adults
  • 7. tPA window is 4.5 hours
  • 8. tPA needs BP <185/110
  • 9. DKA: replete K+ before insulin
  • 10. Hyponatremia: correct ≤8 mEq/L/24h
  • 11. CURB-65 ≥2 means admit
  • 12. CHA2DS2-VASc ≥2 (men) anticoagulate
  • 13. Idarucizumab for dabigatran, not Xa
  • 14. SJS <10% BSA, TEN >30%

USMLE Step 3

  • Practice Questions 234 questions Study Guide 41 topics Cheat Sheet 125 facts Flashcards 50 cards Videos 1 video Blogs 1 blog 1 Job Wiki Free CE Podcast