## Clinical Diagnosis of Deep Vein Thrombosis **Key Point:** Unilateral calf swelling with pitting edema is the most sensitive clinical sign for DVT, though it lacks specificity. No single clinical sign is both sensitive and specific for DVT diagnosis. ### Clinical Signs of DVT: Sensitivity and Specificity | Clinical Sign | Sensitivity | Specificity | Comments | |---|---|---|---| | **Unilateral calf swelling + edema** | 70–80% | 40–50% | Most sensitive; poor specificity | | **Homan's sign** (calf pain on dorsiflexion) | 30–40% | 60% | Low sensitivity; unreliable | | **Pratt's sign** (pain in thigh on compression) | 20–30% | 70% | Very low sensitivity | | **Calf tenderness alone** | 50% | 30% | Nonspecific; many causes | | **Fever** | 15–20% | 80% | Uncommon in DVT | **High-Yield:** Clinical examination alone is insufficient to diagnose or exclude DVT. Sensitivity of clinical signs ranges from 30–80%, and specificity is often <60%. **Always use imaging (compression ultrasound) to confirm or exclude DVT.** ### Why Swelling + Edema Is Most Sensitive 1. Reflects obstruction to venous return 2. Occurs in majority of proximal DVT cases 3. Detectable on inspection and measurement 4. However, swelling can occur from cellulitis, lymphedema, or muscle injury → low specificity **Warning:** Homan's sign is classically taught but has poor sensitivity (30–40%) and is unreliable. Do NOT rely on it clinically. **Clinical Pearl:** Up to 50% of patients with DVT may have *no* clinical signs. Conversely, 50% of patients with clinical signs of DVT do NOT have DVT on imaging. This is why **compression ultrasound is the gold standard** for diagnosis.
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