Venous thromboembolism

Quick Overview

Venous thromboembolism (VTE) encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), affecting ~1-2/1000 annually in the UK. NICE NG158 (2020) provides evidence-based guidance on diagnosis, anticoagulation choice, and duration. Rapid risk stratification using Wells score and appropriate D-dimer interpretation prevents both missed diagnoses and unnecessary imaging.

Core Facts & Concepts

Wells Score for DVT (≥2 = DVT likely, <2 = DVT unlikely):

• Active cancer (+1), paralysis/immobilization (+1), bedridden >3 days/major surgery within 12 weeks (+1)
• Localized tenderness along deep veins (+1), entire leg swollen (+1)
• Calf swelling >3cm vs asymptomatic leg (+1), pitting oedema (+1)
• Collateral superficial veins (+1), alternative diagnosis as likely (-2)

Wells Score for PE (>4 = PE likely, ≤4 = PE unlikely):

• Clinical DVT signs (+3), PE most likely diagnosis (+3), heart rate >100 (+1.5)
• Immobilization/surgery in previous 4 weeks (+1.5), previous VTE (+1.5)
• Haemoptysis (+1), malignancy (+1)

D-dimer Interpretation:

• Use only if Wells score = "unlikely" (negative predictive value >99%)
• Age-adjusted threshold: age × 10 μg/L if >50 years (improves specificity)
• 📊 False positives: pregnancy, malignancy, infection, post-operative, elderly

Anticoagulation per NICE NG158:

• First-line: Apixaban or Rivaroxaban (DOACs) - no monitoring required
• Alternative DOACs: Edoxaban or Dabigatran (require initial LMWH for ≥5 days)
• Warfarin: Use if DOACs contraindicated (renal failure CrCl <15, antiphospholipid syndrome)

Problem-Solving Approach

Step-by-step VTE diagnosis:

1. Calculate Wells score - determines imaging pathway
2. If "unlikely": D-dimer → negative = stop; positive = imaging
3. If "likely": Proceed directly to imaging (DVT: compression USS; PE: CTPA)
4. Interim anticoagulation: Start immediately if imaging delayed >4 hours

Anticoagulation Duration (NICE NG158):

• Provoked VTE (surgery, trauma, oestrogen, pregnancy): 3 months
• Unprovoked VTE: 3-6 months, then reassess bleeding vs recurrence risk
• Active cancer: 3-6 months (consider extended with LMWH or DOAC)
• Recurrent unprovoked VTE: Consider lifelong anticoagulation

🚩 Red Flags for Extended Anticoagulation: Unprovoked proximal DVT/PE, recurrent VTE, antiphospholipid syndrome, active cancer

Thrombophilia Screening Indications (NICE NG158 does NOT routinely recommend):

• Consider only if: age <50, recurrent VTE, unusual site (mesenteric, cerebral), strong family history
• Tests: Factor V Leiden, Prothrombin G20210A, Protein C/S, Antithrombin, Antiphospholipid antibodies

Analysis Framework

DOAC vs Warfarin Selection:

• DOAC preferred unless: severe renal failure (CrCl <15), antiphospholipid syndrome, mechanical heart valves
• Warfarin if patient preference for monitoring or concerns about adherence/cost

Visual Aid

Key Points Summary

✓ Wells score determines pathway: "Unlikely" = D-dimer first; "Likely" = direct imaging (DVT: USS, PE: CTPA)

✓ Age-adjusted D-dimer (age × 10 μg/L if >50 years) reduces false positives in elderly without missing VTE

✓ NICE NG158 first-line: Apixaban or Rivaroxaban (no monitoring); reserve warfarin for CrCl <15 or antiphospholipid syndrome

✓ Duration: Provoked = 3 months; Unprovoked = 3-6 months then reassess; Cancer/recurrent = consider extended

✓ Thrombophilia screening NOT routine - only if age <50, recurrent VTE, unusual site, or strong family history

✓ Interim anticoagulation: Start immediately if imaging delayed >4 hours (prevents clot extension)

✓ Common pitfall: Using D-dimer in "likely" Wells score or high pre-test probability (leads to false reassurance if negative)