Measurement of hemostatic factors in EDTA plasma

This study determined whether immunoassays of factors VII (FVII) and VIII (FVIII) and von Willebrand factor (vWF) in EDTA-anticoagulated plasma samples are comparable to bioassays and immunoassays of these factors in citrate-anticoagulated plasma. Blood from 40 healthy volunteers was collected in EDTA- and citrate-anticoagulant tubes and assayed using immunoassays (EDTA and citrate) and clotting assays (citrate). Linear regression analyses were performed and Pearson correlation coefficients recorded. The correlation coefficients (95% confidence intervals [CIs]) between levels in EDTA- and citrate-anticoagulated plasma samples were 0.893 (0.806-0.943) for FVII antigen (ag), 0.930 (0.870-0.962) for FVIIIag, 0.990 (0.981-0.995) for vWFag, and 0.949 (0.906-0.973) for vWF activity. Coefficients (CIs) were 0.811 (0.668-0.896) for FVII coagulant activity (c) in citrate and FVIIag in EDTA and 0.608 (0.366-0.774) for FVIIIc in citrate and FVIIIag in EDTA. Measurements of FVII, FVIII, and vWF antigens in EDTA-anticoagulated plasma samples give values comparable to similar measurements in citrate-anticoagulated samples. Clotting activity, especially of FVIII, is less well correlated. Although antigen assays using EDTA are not recommended for patients with coagulopathies, they may be suitable for population-based studies.