PO-61 Measurement of procoagulant activity of microparticles by the fibrin generation test as a predictor for venous thrombosis in cancer patients

Abstract

Background: Although in patients with cancer the risk of venous thromboembolism (VTE) is increased, the incidence is too low to routinely give prophylactic treatment. Procoagulant microparticles (MPs), especially tissue factor (TF)-bearing MPs, contribute to the risk of VTE in cancer patients. In the present study, we assessed the MP-associated procoagulant activity using a functional assay, the fibrin generation test (FGT), to identify cancer patients who will develop VTE. Methods: As an ongoing study, plasma was collected from cancer patients, mainly with stage III or IV pancreatic, gastro-intestinal, breast or lung cancer. The MP-associated procoagulant activity was determined via the FGT with the addition of an inhibitory antibody to factor VII. The prolongation of the clotting time in the presence of anti-factor VII is a measure for the contribution of TF-bearing MPs to the clotting time. Patients were followed up for 6 months. Preliminary results: 100 patients were included, of which 77 had complete follow-up. The first 43 patients were used to establish a cut-off value of the FGT. Receiver operating characteristics showed that a prolongation of the clotting time of 13% after addition of anti-factor VII, was the optimal cut-off value. In the entire group, 8 of 77 patients (10%) developed VTE, of which 7 could have been predicted by the FGT. Using this cut-off value, 23 patients (30%) had a FGT-result above the cut-off (positive test) and 54 patients had a FGT-result below the cut-off (negative test). The prevalence of VTE was 30% in the FGT-positive patients and 2% in the FGT-negative patients (sensitivity 88%, specificity 77%). Conclusion: The FGT seems an excellent predictor for VTE in cancer patients. The next step will be to test the efficacy of prophylactic anticoagulants in patients with cancer and a high thrombosis risk based on the FGT.