Deep vein thrombosis — the diagnostic algorithm and the anticoagulation

The diagnostic algorithm:

1. The Wells-DVT score (the clinical prediction rule: the signs, the risk factors and the alternative-diagnosis judgement).^[1]
2. The DVT likely (the 2 or above) → the compression ultrasound directly, with empirical anticoagulation if the scan is delayed.^[1]
3. The DVT unlikely (the 1 or below) → the age-adjusted D-dimer (age times 10 micrograms per litre above 50). If negative, the DVT is ruled out; if positive, the compression ultrasound.^[1][4]
4. The compression ultrasound is the diagnostic test (the non-compressible vein). The proximal (the repeat in one week if the initial is negative and the D-dimer is positive) or the whole-leg strategy.^[1]

The choice of the anticoagulation by the scenario:

• The standard (the most) → the direct oral anticoagulant (the rivaroxaban, the apixaban), started directly with no parenteral lead-in.^[2]
• The cancer-associated → the low-molecular-weight heparin (the dalteparin) first-line, with a DOAC an increasingly used alternative.^[3]
• The pregnancy → the low-molecular-weight heparin (the direct oral anticoagulants and the warfarin contraindicated), continued at least 6 weeks postpartum for a minimum of 3 months.^[5]
• The renal failure → the unfractionated heparin or the dose-adjusted low-molecular-weight heparin.^[2]
• The contraindication to the anticoagulation → the removable IVC filter, retrieved once anticoagulation can start — never a substitute for anticoagulation.^[2]

The duration:

• The provoked (the reversible trigger) → the 3 months.^[2]
• The unprovoked → the 3 months then the reassessment, often the indefinite (the high recurrence).^[2]
• The cancer-associated, the recurrent, the antiphospholipid → the indefinite.^[3]

The principles: the Wells score and the D-dimer to avoid the over-investigation; the compression ultrasound as the diagnostic test; the direct oral anticoagulant for most and the low-molecular-weight heparin for the cancer and the pregnancy; and the duration matched to the recurrence risk.^[1][2]