Patients who have their first VTE under 40 years of age

Patients with oestrogen therapy or pregnancy as the sole risk factor for VTE

Patients who have their first unprovoked VTE under 60 years of age

Patients with recurrent VTE, irrespective of risk factor presence

Patients with recurrent superficial vein thrombosis in the absence of varicose veins

Patients with VTE at unusual sites under 50 years of age

Patients with warfarin-induced skin necrosis and neonates with purpura fulminans not related to sepsis

Asymptomatic individuals with symptomatic first-degree relatives who have thrombophilia