Microparticle-associated tissue factor activity and venous thrombosis in multiple myeloma.

Multiple myeloma (MM) is associated with an increased risk of venous thromboembolic (VTE) complications. Aim of this study was to measure microparticle-associated tissue factor (MP-TF) activity in patients with newly diagnosed MM before and after chemotherapy and to investigate whether MP-TF activity is associated with VTE. MP-TF activity was assessed in 122 newly diagnosed MM patients who were eligible for combination chemotherapy. MP-TF activity levels (17.6 fM Xa/min [8.6-33.2] (median [IQR]) were higher in untreated MM patients compared to normal healthy volunteers (4.1 fM Xa/min [2.3-6.6], p <0.001). MP-TF activity prior to the start of treatment was not different between patients who developed a VTE during follow-up (n=15) and those who did not (n=107). In 75 patients in whom plasma was obtained before and after chemotherapy, MP-TF activity decreased significantly (from 17.4 [10.2-32.8] to 12.0 [7.0-18.5] fM Xa/min, P=0.006). MP-TF activity remained, however, elevated in patients who developed VTE (15.1 [10.3-25.2]), in contrast to patients not developing VTE (11.4 [7.0-25.2], P<0.001). In conclusion, MP-TF activity is increased in patients with MM. Whether MP-TF activity has a pathogenetic role in VTE in MM patients remains to be established in future studies.