Reference — Respiratory
Pulmonary Embolism Risk & Diagnosis Reference
The PE workup in order: estimate risk (Wells), rule out when low (D-dimer), and confirm with imaging (CT angiography). Know what each test is for — and which one is the gold standard.
Educational use only. Diagnostic pathways and thresholds are provider-directed and individualized. This reference is an educational aid. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Risk Factors — Virchow’s Triad
Venous stasis: immobility, prolonged surgery, long travel, heart failure, paralysis. Hypercoagulability: cancer, pregnancy/postpartum, estrogen (OCPs/HRT), inherited thrombophilias, sepsis. Endothelial injury: surgery, trauma, fractures, central venous catheters. The more factors present, the higher the suspicion.
The Diagnostic Workup
| Test | Role | Note |
|---|---|---|
| Wells score | Pretest probability (clinical risk) | Stratifies likely vs unlikely; guides whether to use D-dimer or go straight to imaging |
| D-dimer | Rule OUT (when probability is low) | Sensitive, not specific — a normal value helps exclude; many things raise it |
| CT pulmonary angiography (CTA) | Confirm (GOLD STANDARD) | Visualizes the clot; needs IV contrast (check renal function/allergy) |
| V/Q scan | Alternative confirmatory test | Used when CTA is contraindicated (contrast allergy, renal failure, pregnancy) |
| ABG | Supports, not diagnostic | Classic = hypoxemia with respiratory alkalosis (tachypnea blows off CO₂) |
| Troponin / BNP | Severity / RV strain | Elevation suggests right-ventricular strain (submassive/massive PE) |
ECG may show sinus tachycardia (most common) or the classic-but-uncommon S1Q3T3 pattern of RV strain.
NCLEX Pearls
- ✦Risk = Virchow's triad: venous stasis, hypercoagulability, endothelial injury.
- ✦Wells score sets pretest probability; D-dimer rules OUT when probability is low (sensitive, not specific).
- ✦CT pulmonary angiography is the gold standard; V/Q scan is the alternative (renal failure, contrast allergy, pregnancy).
- ✦Classic ABG = hypoxemia with respiratory alkalosis; troponin/BNP rise with RV strain.
- ✦ECG: sinus tachycardia is most common; S1Q3T3 is classic but uncommon.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with American Association for Respiratory Care (AARC) · GOLD (COPD) / ATS / CHEST. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →