Stability of coagulation proteins in frozen plasma.
ABSTRACT This study reports on the frozen stability of all commonly measured coagulation proteins in normal citrated plasma: activated partial thromboplastin time, prothrombin time (%), thrombin time and fibrinogen (Clauss); clotting assays for factors II, V, VII, VIII, IX, X, XI and XII; functional assays for protein C (clotting), protein S (clotting), antithrombin (chromogenic) and plasminogen (chromogenic); and immunological assays for von Willebrand factor and D-dimer. All these factors listed are stable for up to 3 months if frozen at -24 degrees C or lower. At -74 degrees C, all these factors (allowing for 10% variation) were stable for at least 18 months, most were stable for 24 months. The number of proteins showing > 5% variation over baseline after 6 months storage indicates that some decay does occur even at -74 degrees C. There was no clear advantage in snap freezing at -74 degrees C and then storing at -24 degrees C over both freezing and storing at -24 degrees C; therefore, the freezing process itself is not responsible for the loss of stability. The best stability, especially at -24 degrees C, was obtained when small samples (1 ml) were stored in screw-cap tubes with a minimum dead space. The decrease in stability of the coagulation proteins directly correlates with the effect of temperature and time.
- [Show abstract] [Hide abstract]
ABSTRACT: D-dimer concentrations have not been evaluated extensively as a predictor of increased venous thromboembolism (VTE) risk in acutely ill, hospitalized medical patients. To analyze the relationships between D-dimer concentration, VTE, and bleeding in the MAGELLAN trial (NCT00571649). Multicenter, randomized, controlled trial. Patients aged ≥40 years, hospitalized for acute medical illnesses with risk factors for VTE received subcutaneous enoxaparin 40 mg once daily for 10 ± 4 days then placebo up to Day 35, or oral rivaroxaban 10 mg once daily for 35 ± 4 days. Patients (n = 7581) were grouped by baseline D-dimer ≤2× or >2× upper limit of normal. VTE and major plus non-major clinically relevant bleeding were recorded at Day 10, Day 35, and between Days 11 and 35. VTE frequency was 3.5-fold greater in patients with high D-dimer concentrations. Multivariate analysis showed D-dimer was an independent predictor of VTE risk (odds ratio 2.29 [95% confidence interval 1.75-2.98]), and was similarly predictive for VTE to established risk factors, e.g. cancer and advanced age. In the high D-dimer group, rivaroxaban was non-inferior to enoxaparin at Day 10, and, unlike the low D-dimer group, superior to placebo at Day 35 (P < 0.001) and Days 11-35 (P < 0.001). In both groups, bleeding outcomes favored enoxaparin/placebo. Elevated baseline D-dimer concentrations may identify acutely ill, hospitalized medical patients at high VTE risk for whom extended anticoagulant prophylaxis may provide greater benefit than those with low D-dimer concentrations. This article is protected by copyright. All rights reserved.Journal of Thrombosis and Haemostasis 01/2014; · 6.08 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Introduction Where unexplained recurrent pregnancy loss (RPL) is attributed to an underlying maternal prothrombotic state, empirical prophylactic anticoagulation may be recommended. Materials and Methods In the present study we used calibrated automated thrombography and rotational thromboelastometry to determine the procoagulant potential of these women as a rationale for anticoagulation. Fifty women with ≥ three consecutive unexplained losses prior to 14 weeks’ gestation or one loss after this time were compared with forty-one parous women with no miscarriages. Exclusion criteria included antiphospholipid syndrome, inherited thrombophilia and prior venous thromboembolism. Thrombin generation in platelet poor plasma and whole blood thromboelastometry was performed outside pregnancy to determine the presence or not of an underlying prothrombotic state. Results Peak thrombin and endogenous thrombin potential were not significantly increased in subjects relative to controls. The use of low tissue factor (1 pM) to better reflect physiological conditions and assay modification to better assess the protein C pathway (5 pM in the presence of thrombomodulin) provided no additional discrimination. Consistent results were shown with thromboelastometry; mean parameters were equivalent between subjects and controls. Conclusions These data demonstrate that global coagulation assays provide no evidence of an underlying hypercoagulable state in women with unexplained RPL; this is in keeping with the results of recent randomised controlled trials and strengthens the evidence base against use of anticoagulants in this setting.Thrombosis Research 01/2014; · 3.13 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Background The risk of venous thrombosis (VT) associated with oral hormone therapy (HT) may differ by type of estrogen compound.Objective To compare the thrombotic profile of women using oral conjugated equine estrogens (CEE) with that of women using oral estradiol (E2).Methods In postmenopausal female health maintenance organization (HMO) members with no history of VT, we measured thrombin generation, levels of factor VII activity, antithrombin activity, and total protein S antigen. Mean levels of hemostasis biomarkers were cross-sectionally compared by use and type of estrogen using multiple linear regressions. The type of estrogen used was determined primarily by the HMO formulary, which changed its preferred estrogen from CEE to E2 during the study period.ResultsThe sample included 92 E2 users and 48 CEE users, with a mean age of 64.1y and mean BMI of 29.1kg/m2. Twenty-seven percent of HT contained medroxyprogesterone acetate. Compared with E2 users, CEE users had greater thrombin generation peak values, endogenous thrombin potential, and lower total protein S (multivariate adjusted differences of 49.8 nM (95%CI: 21.0, 78.6); 175.0 nMxMin (95%CI: 54.4, 295.7); and -13.4% (95%CI: -19.8, -6.9), respectively). Factor VII and antithrombin levels were not different between E2 and CEE users. Results were similar in subgroups of users of unopposed HT, opposed HT, low-dose estrogen and standard dose estrogen.Conclusion The hemostatic profile of women using CEE is more prothrombotic than that of women using E2. These findings provide further evidence for a different thrombotic risk for oral CEE and oral E2.This article is protected by copyright. All rights reserved.Journal of Thrombosis and Haemostasis 03/2014; · 6.08 Impact Factor