Comparison of a fluorogenic anti-FXa assay with a central laboratory chromogenic anti-FXa assay for measuring LMWH activity in patient plasmas

Obstetric venous thromboembolism: a systematic review of dalteparin and pregnancy

A systematic review of studies published between 1 January 1985 and 31 August 2017 was performed to analyse the efficacy of the low-molecular-weight heparin, dalteparin, in venous thromboembolism (VTE) treatment and prophylaxis during pregnancy, and to evaluate dosing practices, anticoagulant monitoring and adverse events. A therapeutic dosing throughout pregnancy or followed by reduced doses effectively prevented VTE recurrence. Anti-factor Xa activity was the most commonly used method of dose monitoring. The risk of bleeding with dalteparin was generally minor. Major bleeding was observed when a high dose of dalteparin was employed during (or close to) delivery, or postpartum. Other adverse events were minor. Disparity exists in VTE treatment and thromboprophylaxis, with wide variety in the dosing regimens, treatment strategies and monitoring practices employed. Large randomised controlled trials are warranted but due to ethical reasons, and the rarity of VTE-associated obstetric complications, case-control, registry and large observational studies present more likely options.

Factor Xa generation by computational modeling: an additional discriminator to thrombin generation evaluation

Factor (f)Xa is a critical enzyme in blood coagulation that is responsible for the initiation and propagation of thrombin generation. Previously we have shown that analysis of computationally generated thrombin profiles is a tool to investigate hemostasis in various populations. In this study, we evaluate the potential of computationally derived time courses of fXa generation as another approach for investigating thrombotic risk. Utilizing the case (n = 473) and control (n = 426) population from the Leiden Thrombophilia Study and each individual's plasma protein factor composition for fII, fV, fVII, fVIII, fIX, fX, antithrombin and tissue factor pathway inhibitor, tissue factor-initiated total active fXa generation was assessed using a mathematical model. FXa generation was evaluated by the area under the curve (AUC), the maximum rate (MaxR) and level (MaxL) and the time to reach these, TMaxR and TMaxL, respectively. FXa generation was analyzed in the entire populations and in defined subgroups (by sex, age, body mass index, oral contraceptive use). The maximum rates and levels of fXa generation occur over a 10- to 12- fold range in both cases and controls. This variation is larger than that observed with thrombin (3–6 fold) in the same population. The greatest risk association was obtained using either MaxR or MaxL of fXa generation; with an ∼2.2 fold increased risk for individuals exceeding the 90^th percentile. This risk was similar to that of thrombin generation(MaxR OR 2.6). Grouping defined by oral contraceptive (OC) use in the control population showed the biggest differences in fXa generation; a >60% increase in the MaxR upon OC use. FXa generation can distinguish between a subset of individuals characterized by overlapping thrombin generation profiles. Analysis of fXa generation is a phenotypic characteristic which may prove to be a more sensitive discriminator than thrombin generation among all individuals.