Deep vein thrombosis (DVT) and pulmonary embolism (PE) are serious conditions that can lead to significant morbidity and mortality. Risk scores have been developed to assess the likelihood of DVT and PE, guide diagnostic testing, and inform management decisions.
Clinical Use of Risk Scores
- Wells Score for DVT and PE: These scores help stratify patients into low, moderate, or high risk for DVT or PE, guiding the need for further diagnostic testing (e.g., D-dimer, ultrasound, CT pulmonary angiography).
- Revised Geneva Score: An alternative to the Wells Score, particularly useful in emergency settings for assessing PE risk.
- PERC Rule: Used to safely rule out PE in patients with a low pre-test probability, potentially avoiding unnecessary imaging studies.
Here are the commonly used risk scores for DVT and PE:
DVT Risk Scores
Wells Score for DVT
The Wells Score is a clinical prediction rule used to estimate the probability of DVT. It assigns points based on clinical criteria:
- Active cancer (treatment ongoing, within the last 6 months, or palliative): +1
- Paralysis, paresis, or recent plaster immobilization of the lower extremities: +1
- Recently bedridden for more than 3 days or major surgery within the last 4 weeks: +1
- Localized tenderness along the distribution of the deep venous system: +1
- Entire leg swollen: +1
- Calf swelling at least 3 cm larger than the asymptomatic side (measured 10 cm below tibial tuberosity): +1
- Pitting edema confined to the symptomatic leg: +1
- Collateral superficial veins (non-varicose): +1
- Previously documented DVT: +1
- Alternative diagnosis at least as likely as DVT: -2
Interpretation:
- Score 0: Low risk (probability of DVT is <3%)
- Score 1-2: Moderate risk (probability of DVT is 17%)
- Score ≥3: High risk (probability of DVT is 75%)
PE Risk Scores
Wells Score for PE
The Wells Score for PE is a clinical prediction rule to estimate the probability of pulmonary embolism:
- Clinical signs and symptoms of DVT (minimum of leg swelling and pain with palpation of the deep veins): +3
- PE is the most likely diagnosis: +3
- Heart rate >100 beats per minute: +1.5
- Immobilization or surgery in the previous 4 weeks: +1.5
- Previous DVT/PE: +1.5
- Hemoptysis: +1
- Active cancer (treatment ongoing, within the last 6 months, or palliative): +1
Interpretation:
- Score ≤4: PE unlikely (probability of PE is <15%)
- Score >4: PE likely (probability of PE is >15%)
Revised Geneva Score
The Revised Geneva Score is another clinical prediction tool for assessing the probability of PE:
- Age >65 years: +1
- Previous DVT or PE: +3
- Surgery or fracture within 1 month: +2
- Active malignancy: +2
- Unilateral lower limb pain: +3
- Hemoptysis: +2
- Heart rate 75-94 bpm: +3
- Heart rate ≥95 bpm: +5
- Pain on deep venous palpation of lower limb and unilateral edema: +4
Interpretation:
- Score 0-3: Low probability of PE
- Score 4-10: Intermediate probability of PE
- Score ≥11: High probability of PE
PERC (Pulmonary Embolism Rule-out Criteria)
The PERC rule is used in patients with a low pre-test probability of PE to rule out the condition without further testing if all criteria are negative:
- Age <50 years
- Heart rate <100 bpm
- Oxygen saturation ≥95% on room air
- No hemoptysis
- No estrogen use
- No history of DVT or PE
- No unilateral leg swelling
- No surgery or trauma requiring hospitalization within the past 4 weeks
If a patient meets all the PERC criteria and has a low pre-test probability of PE, the likelihood of PE is low enough that further testing is usually not required.
Summary
- Wells Score: Estimates the probability of PE based on clinical signs, symptoms, and history. It requires clinician judgment for certain components.
- Revised Geneva Score: Uses objective criteria to estimate PE probability without requiring clinician judgment.
- PERC Rule: Helps rule out PE in low-risk patients without further testing if all criteria are met.
These tools help clinicians stratify patients based on their risk of PE and make informed decisions about further testing and management.