Table 1.

Known hereditary thrombophilia risk factors

Prevalence in the white population (%)
Thrombophilic defect	Incident VTE	Recurrent VTE	Normal population	Relative thrombotic risk
Antithrombin deficiency	1–2	2–5	0.02–0.04	5
Protein C deficiency	2–5	5–10	0.2–0.5	6–10
Protein S deficiency	1–3	5–10	0.1–1	2
Factor V Leiden	20	40–50	3–7	3–7 (heterozygotes) 50–100 (homozygotes)
Prothrombin G20210A	3–8	15–20	1–3	2–8 (heterozygotes)

VTE venous thromboembolism