Background Rivaroxaban is a direct factor Xa inhibitor with substantial inter‐individual pharmacokinetic (PK) variability. Pharmacodynamic (PD) variability, especially assessed with thrombin generation (TG), has been less documented. Objectives (i) To assess TG parameter time profiles in healthy volunteers, with TG being studied under different conditions and (ii) to model the relationship between rivaroxaban concentrations and TG parameters and subsequently estimate interindividual variability. Methods Sixty healthy male volunteers (DRIVING‐NCT01627665) received a single 40‐mg rivaroxaban dose. Blood sampling was performed at baseline and 10 predefined time points over 24 h. The TG was investigated with the fully automated ST‐Genesia system (Stago), using two tissue‐factor (TF) concentrations, in the absence (−), or presence (+) of thrombomodulin (TM) for the lowest one. The PD models were built to characterize the relationships between plasma rivaroxaban concentrations and endogenous thrombin potential (ETP) or peak height induced by the lowest TF concentration. Results Thrombin generation parameter time profiles with the lowest TF concentration showed a good sensitivity to rivaroxaban, especially +TM (active protein C negative feedback). The relationship between rivaroxaban concentrations and TG parameters was modeled with a sigmoidal relation. Mean rivaroxaban concentrations halving the baseline value of ETP and peak height (−TM) (C50) were of 284 and 33.2 ng/mL, respectively: +TM, C50 declined to 19.4 and 13.8 ng/mL, reflecting a powerful inhibitory effect. The estimated C50 population coefficients of variation were of 12.2% (−TM) and 31.3% (+TM) with the peak height models, 34.8% (+TM) with the ETP model. Conclusions This low‐rivaroxaban to moderate‐rivaroxaban PD variability in healthy volunteers contrasts with the substantial PK variability and deserves to be studied in different patient settings.

Introduction Directs oral anticoagulants (DOACs) can interfere with coagulation assays, especially in thrombophilia workup. To avoid these interferences, a new device, DOAC Filter, allows the removal of DOACs from citrated plasma. This study aims to confirm that DOAC Filter efficiently removes DOACs and to ascertain that coagulation assays are not impacted by filtration. Methods Directs oral anticoagulants Filter (Diagnostica Stago, France) is a filtration cartridge in which DOAC molecules are trapped by noncovalent binding, while plasma is filtered through a solid phase. Normal pool plasma (NPP) spiked with DOACs up to 300 ng/mL, with dabigatran etexilate (n = 27), rivaroxaban (n = 35), apixaban (n = 33), and edoxaban (n = 27) or 120 ng/mL for betrixaban (n = 4), and 18 plasma's samples from DOAC‐treated patients were used to assess efficacy. The potential impact of DOAC Filter on coagulation assays was evaluated with NPP and plasma's samples from positive and negative lupus anticoagulant (LA) patients. Results Directs oral anticoagulants concentrations measured after filtration were below the limit of detection (LoD) of DOAC‐specific assays for all plasmas tested, except for one apixaban plasma sample, with postfiltration concentration slightly higher than anti‐Xa assay LoD (25.1 ng/mL). Coagulation assays results varied between −4 and +8% after filtration and between −6 and +8% for LA plasmas. Such limited variations are not expected to have any clinical impact. Conclusion Directs oral anticoagulants Filter efficiently removes DOACs from plasma and achieves concentrations below DOAC‐specific assays LoD, except in the case of one apixaban sample. The integrity of plasma is respected, and the cartridge seems not to impact LA diagnosis.

Introduction The ST Genesia is a benchtop, fully automated thrombin generation (TG) device. It is completely standardized and ensures a uniform heat distribution throughout the measurement. We aimed to determine reference values and to compare TG in men and women with and without the use of oral contraceptives (OCs). Materials and Methods Plasma from 117 healthy donors was measured on the ST Genesia with the available reagent kits: STG‐BleedScreen, STG‐DrugScreen, and STG‐ThromboScreen. All kits include at least two quality controls and a reference plasma to normalize data. STG‐ThromboScreen has a second trigger containing thrombomodulin (TM) to include the effect on the protein C pathway. Means were compared with one‐way analysis of variance and reference ranges were established with 2.5th to 97.5th percentiles on absolute TG parameters. Results Mean age of the donors was 35 years (SD ± 12); 49.6% were men, 37.6% women without OCs, and 12.8% women with OCs. Men and women without OCs had, respectively, a mean peak height of 167 nM and 164 nM with STG‐BleedScreen, 335 nM and 351 nM with STG‐DrugScreen, and 192 nM and 198 nM with STG‐ThromboScreen. Women taking OCs had a mean peak height of 263 nM, 473 nM, and 312nM, respectively ( P < .05 compared to men/women without OCs). TM decreased endogenous thrombin potential by 54% in men, 47% in women without OCs, and only 25% in women with OCs ( P < .05 compared to men/women without OCs). Conclusions TG in men and women without OCs was similar; however, women taking OCs had significantly higher TG values, and the effect of TM was also less pronounced in these women.

Introduction Thrombin generation (TG) documents hypercoagulability. TG in platelet‐poor plasma is exquisitely sensitive to heparins, which thus must be neutralized before testing. Heparinase and hexadimethrine bromide (polybrene) have been used for that purpose, but their effects per se on TG have been poorly studied so far. Methods (i) TG was studied in commercial normal pooled plasma (NPP; CryoCheck®, Cryopep) in absence or presence of neutralizing agents. (ii) NPP was spiked with increasing concentrations of unfractionated heparin (UFH; up to 1.0 IU/mL) or low‐molecular‐weight heparin (LMWH; enoxaparin up to 1.2 IU/mL) and TG studied after incubation of heparinase (Hepzyme®; 15 minutes) or polybrene (0.025 mg/mL; 10 minutes). Results (i) With ThromboScreen reagent to initiate TG, addition of heparinase was associated with increased peak, whereas polybrene caused lengthening of lag time and time to peak, compared with nonsupplemented NPP. (ii) With polybrene, TG was completely restored over the whole range of UFH and LMWH studied. By contrast, heparinase failed to fully restore TG in presence of UFH concentrations ≥0.8 IU/mL or LMWH concentrations ≥1.0 IU/mL. Those effects were matched with detectable tiny residual amounts of non‐neutralized heparin (as assessed with an anti‐Xa assay) and were less pronounced with a higher picomolar concentration of tissue factor (DrugScreen reagent). Conclusion Polybrene fully restored TG of heparinized plasma at the expense of an alteration of TG, pointing to the need to use adapted reference ranges. Heparinase failed to do so in presence of high concentrations of both heparins.

The distribution of total fibrinolytic activity in seminal plasma, as well as specific tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and plasminogen activator inhibitor (PAI), has been studied using antigen and activity techniques in 170 ejaculates of men attending for assessment because of infertility without genital urinary pathology. Among these 170 patients, 18 showed oligoasthenoteratospermia, 28 showed azoospermia, and 124 showed normozoospermia. The seminal values were 50 times higher (262 to 289 ng/mL in antigen and 179 to 199 x 10 (3) IU/L for activity) than values in blood for t-PA and 15 times higher than values in blood for u-PA (18.4 to 26 ng/mL and 1.5 to 2.4 IU/mL, respectively). There was no correlation between the two levels in antigen or activity, but a higher concentration was observed in all first fractions from split ejaculates measurements. Moreover, t-PA was significantly lower in semen with abnormal liquefaction compared with semen exhibiting normal liquefaction. Zymography confirms the active forms. PAI was absent or at the detection limit for normozoospermia, whereas patients with oligoasthenoteratospermia or azoospermia showed high PAI antigen and activity levels. These data demonstrate that seminal PA activity may be related to sperm fertilizing capacity.