Effect of warfarin prophylaxis on venous thrombosis in patients with paroxysmal nocturnal hemoglobinuria (PNH) granulocyte clone sizes of > 50% (patients presenting with thrombosis excluded).

The 10-year cumulative incidence rate of venous thrombosis in patients with PNH granulocyte clones of > 50%, not presenting with thrombosis and not taking warfarin is 36.5%. In comparison, the current thrombosis rate is 0% in patients taking primary prophylaxis (P = 0.01*).

Thirty-two of the 39 patients on primary prophylaxis had granulocyte clone sizes > 50% and could therefore be included in this analysis. A further 2 of these patients were excluded because, having stopped warfarin (one through personal choice and one because of warfarin-associated hemorrhage), they went on to suffer venous thrombosis.

Time 0 was the time of presentation with PNH.

* P value calculated with use of the log-rank test;