How you got that clot
Elevated plasma factor VIII predicts recurrent venous thromboembolism.
LONDON, August 17 (SPIS MedWire). An elevated plasma level of factor VIII is a known risk factor for venous thromboembolism but, according to a report in today's New England Journal of Medicine it is also strongly predictive of recurrence of the condition. Kyrle et al from Vienna University Hospital used data from the ongoing Austrian Study on Recurrent Venous Thrombosis to prospectively evaluate the relationship between raised factor VIII levels and recurrence in 360 patients who had already had a first episode of venous thrombosis. Over an average follow-up period of 30 months, during which oral anticoagulation was discontinued, 38 patients had recurrence of thromboembolism (24 deep vein thrombosis, 14 pulmonary embolism). Patients with recurrence had higher mean (±SD) plasma levels of factor VIII than those without recurrence (182±66 vs 157±54 IU/dl, p=0.009). The relative risk of recurrent venous thrombosis was 1.08 (95% CI 1.04–1.12) for each increase of 10 IU/dl in the plasma level of factor VIII. Among patients with a factor VIII level above the 90th percentile of the values in the study population, the likelihood of recurrence at two years was 37%, as compared with 5% among patients with lower levels (p<0.001). Among patients with plasma factor VIII levels above the 90th percentile, as compared with those with lower levels, the overall relative risk of recurrence was 6.7 (95% CI, 3.0–14.8) after adjustment for age, sex, the presence of factor V Leiden or prothrombin mutation, and the duration of oral anticoagulation. The authors call for prospective studies of anticoagulation in these patients, but add that "until these data are in hand, extended prophylaxis must be considered after a single episode of spontaneous venous thromboembolism."