What are the risk scoring systems for Deep Vein Thrombosis (DVT)?

Risk Scoring Systems for Deep Vein Thrombosis (DVT)

The Wells score is the most validated and recommended risk stratification tool for DVT, which should be used as the first step in clinical assessment to determine pretest probability before ordering diagnostic tests. 1, 2

Primary Risk Scoring Systems

Wells Score for DVT

• Consists of clinical criteria that stratify patients into low, moderate, or high probability categories based on risk factors, physical findings, and likelihood of alternative diagnoses 2
• Points are assigned for: active cancer (1), paralysis/recent immobilization (1), bedridden >3 days or major surgery (1), localized tenderness along deep veins (1), entire leg swelling (1), calf swelling >3cm compared to asymptomatic leg (1), pitting edema (1), collateral superficial veins (1), previous DVT (1), and alternative diagnosis at least as likely as DVT (-2) 2
• Categorizes patients into risk groups: low risk (<1 point), moderate risk (1-2 points), or high risk (≥3 points) 2, 1
• Prevalence of DVT ranges from 5% (low), 17% (moderate), to 53% (high) pretest probability 2

Modified Wells Score

• Includes previous DVT as an additional criterion 3
• Similar performance to the original Wells score for proximal DVT detection, with comparable area under the receiver operating characteristic curve 4
• Classifies slightly fewer patients as low-risk (48% vs 53%) and more as high-risk (17% vs 15%) compared to the original score 4

Diagnostic Approach Using Risk Scores

Low to Moderate Pretest Probability

• Patients with low or moderate pretest probability should undergo high-sensitivity D-dimer testing first 2
• A negative D-dimer result in low-risk patients excludes DVT with 99% negative predictive value, avoiding unnecessary imaging 2, 1
• If D-dimer is positive, proceed to compression duplex ultrasound 2, 1

High Pretest Probability

• Patients with high pretest probability should proceed directly to compression duplex ultrasound without D-dimer testing 2, 1
• The failure rate of the Wells score to classify patients with a low pretest probability is 5.9% 5

Additional Risk Scoring Systems

Padua Prediction Score

• Used primarily for VTE prophylaxis in hospitalized medical patients 2
• Includes: active cancer (3), previous VTE (3), reduced mobility (3), thrombophilia (3), recent trauma/surgery (2), age ≥70 (1), heart/respiratory failure (1), acute MI or stroke (1), acute infection/rheumatic disorder (1), BMI ≥30 (1), ongoing hormonal treatment (1) 2
• Score ≥4 indicates high risk requiring prophylaxis 2

IMPROVE VTE Risk Assessment Model

• Used for hospitalized medical patients to assess VTE risk 2
• Includes: previous VTE (3), known thrombophilia (2), lower limb paralysis (2), active cancer (2), immobilization >7 days (1), ICU/CCU stay (1), age >60 years (1) 2
• Score ≥2 indicates increased VTE risk requiring prophylaxis 2

Caprini Score

• Used primarily for surgical patients to stratify VTE risk 2
• Stratifies patients into four risk categories: very low (0 points; 0.5% risk), low (1-2 points; 1.5% risk), moderate (3-4 points; 3% risk), and high (>5 points; 6% risk) 2

Limitations and Special Considerations

• The Wells score performs poorly in inpatient settings with an area under the ROC curve of only 0.60, which is only slightly better than chance 5
• The Wells score has a higher failure rate and lower efficiency in inpatients compared to outpatients 5
• Neither the original nor modified Wells score appears particularly useful in hospitalized patients and those with isolated distal DVT 4
• In patients with comorbid conditions likely to cause elevated D-dimer (cancer, recent surgery, infection), D-dimer testing has limited utility and direct imaging should be considered 1

Clinical Implications

• Using clinical risk stratification with D-dimer testing can reduce unnecessary ultrasound examinations by up to 30% 1, 6
• For patients with a positive ultrasound for proximal DVT, anticoagulation should be started unless contraindicated 3
• For distal DVT, patients can either start anticoagulation or undergo serial ultrasound monitoring 3
• Risk scores should guide not only diagnosis but also influence decisions about duration of anticoagulation therapy 6