What should be assessed in a patient with a new Deep Vein Thrombosis (DVT)?

Assessment of New Deep Vein Thrombosis

In a patient with newly diagnosed DVT, you must assess clinical probability using a validated scoring system, obtain baseline laboratory tests (CBC with platelets, PT, aPTT, liver and kidney function), and perform complete duplex ultrasound from the inguinal ligament to the ankle to fully characterize the thrombus extent. 1, 2

Clinical Probability Assessment

Use the Wells Score to stratify pretest probability before or immediately after diagnosis confirmation 1:

• Active cancer (treatment within 6 months or palliative): +1 point 1
• Paralysis, paresis, or recent plaster immobilization: +1 point 1
• Recently bedridden ≥3 days or major surgery within 12 weeks: +1 point 1
• Localized tenderness along deep venous system: +1 point 1
• Entire leg swollen: +1 point 1
• Calf swelling ≥3 cm larger than asymptomatic side (measured 10 cm below tibial tuberosity): +1 point 1
• Pitting edema confined to symptomatic leg: +1 point 1
• Collateral superficial veins (nonvaricose): +1 point 1
• Previously documented DVT: +1 point 1
• Alternative diagnosis at least as likely: -2 points 1

A score ≥2 indicates high probability; <2 indicates low probability 1.

Baseline Laboratory Testing

Obtain the following labs as part of initial diagnostic workup 2:

• Complete blood count with platelet count - essential for baseline before anticoagulation and to assess for heparin-induced thrombocytopenia risk 2
• PT and aPTT - baseline coagulation parameters 2
• Liver function tests - important for anticoagulant selection and dosing 2
• Kidney function (creatinine/CrCl) - critical for LMWH and DOAC dosing decisions 1, 2

Complete Imaging Assessment

Complete duplex ultrasound (CDUS) is the preferred imaging modality and should include 1:

• Compression of deep veins from inguinal ligament to ankle at 2-cm intervals, including posterior tibial and peroneal veins in the calf 1
• Spectral Doppler waveforms of bilateral common femoral veins to evaluate symmetry 1
• Popliteal spectral Doppler 1
• Color Doppler images throughout 1

Evaluate symptomatic areas for superficial venous thrombosis or alternative pathology, particularly if deep vein assessment is normal 1. Limited protocols that exclude calf veins are not recommended as they require repeat scanning in 5-7 days 1.

Assessment for Pulmonary Embolism

Consider evaluating for concurrent PE if the patient has any respiratory symptoms (dyspnea, chest pain, tachypnea), as DVT and PE represent the same disease spectrum 1. Use clinical probability assessment (Wells PE score) combined with D-dimer if PE unlikely, or proceed directly to CT pulmonary angiography if PE likely 1.

Provoked vs Unprovoked Classification

Determine if the DVT is provoked or unprovoked, as this impacts duration of anticoagulation 1:

• Provoked: Recent surgery, trauma, immobilization, pregnancy, estrogen therapy 1
• Unprovoked: No identifiable transient risk factor - requires longer anticoagulation 1

Cancer Screening Considerations

In patients with unprovoked DVT, assess for occult malignancy through age-appropriate cancer screening 1, 2. Active cancer is present in approximately 10% of patients with unprovoked VTE 1. Cancer patients require different anticoagulation strategies (LMWH preferred over warfarin) 2, 3.

Common Pitfalls to Avoid

• Do not rely on clinical examination alone - the positive predictive value of history and physical examination is poor, with DVT prevalence of 15% even in "low-risk" clinical groups 4
• Do not accept limited proximal-only ultrasound as definitive - this requires repeat imaging in 5-7 days and may miss isolated calf DVT 1
• Do not forget to assess renal function before selecting anticoagulation - LMWH accumulates with CrCl <30 mL/min and fondaparinux is contraindicated 1
• Do not overlook bilateral symptoms - consider alternative diagnoses like heart failure, venous insufficiency, or lymphedema 2