Summary
Hereditary deficiencies of protein S, protein C and antithrombin are known risk factors
for first venous thromboembolism. We assessed the absolute risk of recurrence, and
the contribution of concomitant thrombophilic defects in a large cohort of families
with these deficiencies. Annual incidence of recurrence was estimated in 130 deficient
patients, with separate estimates for those with each of protein S, protein C, and
antithrombin deficiency, and in eight non-deficient patients with prior venous thromboembolism.
All patients were also tested for factor V Leiden, prothrombin G20210A, high levels
of factors VIII, IX and XI, and hyperhomocysteinemia. There were 81 recurrent events
among 130 deficient patients. Median follow-up was 4.6 years. Annual incidences (95%
confidence interval) of recurrent venous thromboembolism were 8.4% (5.8–11.7) for
protein S deficiency, 6.0% (3.9–8.7) for protein C deficiency, 10.0% (6.1–15.4) for
antithrombin deficiency, and overall 7.7% (6.1–9.5). Relative risk of recurrence in
patients with a spontaneous versus provoked first event was 1.5 (0.95–2.3). Cumulative
recurrence rates at 1, 5 and 10 years were 15%, 38% and 53%. Relative risk of recurrence
with concomitant defects was 1.4 (0.7–2.6) (1 defect) and 1.4 (0.8–2.7) (≥2 defects).
Annual incidence was 1.0% (0.03–5.5) in eight non-deficient patients. Annual incidence
of major bleeding in deficient patients on oral anticoagulant treatment was 0.5% (0.2–1.0).
We conclude that patients with a hereditary protein S, protein C or antithrombin deficiency
appear to have a high absolute risk of recurrence. This risk is increased after a
first spontaneous event, and by concomitance of other thrombophilic defects.
Keywords
Epidemiology - recurrent venous thromboembolism - thrombophilia