Letter by Martin et al Regarding Article, “Linking Endogenous Factor Xa Activity, a Biologically Relevant Pharmacodynamic Marker, to Edoxaban Plasma Concentrations and Clinical Outcomes in the ENGAGE AF-TIMI 48 Trial”

SummaryComparative plasma heparin levels were measured in normal subjects injected subcutaneously with 5,000 units of the sodium and calcium salts of heparin. Plasma heparin levels were measured up to 7 hr post-injection by an anti-factor Xa assay (Denson and Bonnar 1973). Preliminary studies indicated that heparin levels were reproducible in subjects who received two injections of the same heparin. Peak plasma concentrations (Cmax) and the time at which peak concentration was reached (Tmax) varied greatly from subject to subject. In one group of subjects (15) two commonly used heparins, a sodium heparin (Evans) and a calcium heparin (Choay) were compared. Peak heparin concentrations were not significantly different. However the Tmax for the sodium heparin (1.5 hr) was significantly earlier than the Tmax for the calcium heparin (3 hr) and this was not due to a difference in the volume of the two heparin injections. No significant difference could be detected in the plasma clearance rate and the molecular weight distribution of the two heparins.In two other groups of subjects, sodium and calcium preparations from two manufacturers were compared. In general, the sodium salts gave rise to significantly higher plasma concentrations, which could be interpreted as a greater bioavailability of sodium salts. These results indicate that the salt of the heparin can influence the plasma concentration achieved after subcutaneous injection.

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Coagulation and Fibrinolytic Profile of Paediatric Patients Undergoing Cardiopulmonary Bypass

Thrombosis and Haemostasis ◽

10.1055/s-0038-1655952 ◽

1997 ◽

Vol 77 (02) ◽

pp. 270-277 ◽

Cited By ~ 120

Author(s):

Anthony K C Chan ◽

Michael Leaker ◽

Frederick A Burrows ◽

William G Williams ◽

Colleen E Gruenwald ◽

...

Keyword(s):

Cardiopulmonary Bypass ◽

Plasminogen Activator ◽

Plasma Concentrations ◽

Factor Xa ◽

Plasminogen Activator Inhibitor ◽

Protein S ◽

Poor Correlation ◽

Heparin Cofactor Ii ◽

Paediatric Patients ◽

Sick Children

SummaryThe haemostatic system and the use of heparin during cardiopulmonary bypass (CPB) have been studied extensively in adults but not in children. Results from adult trials cannot be extrapolated to children because of age-dependent physiologic differences in haemostasis. We studied 22 consecutive paediatric patients who underwent CPB at The Hospital for Sick Children, Toronto. Fibrinogen, factors II, V, VII, VIII, IX, XI, XII, prekallikrein, protein C, protein S, antithrombin (AT), heparin cofactor II, α2-macroglobulin, plasminogen, α2-antiplas- min, tissue plasminogen activator (tPA), plasminogen activator inhibitor, thrombin-AT complexes (TAT), D-dimer, heparin (by both anti-factor Xa assay and protamine titration) and activated clotting time (ACT) were assayed perioperatively. The timing of the sampling was: pre heparin, post heparin, after initiation of CPB, during hypothermia, post hypothermia, post protamine reversal and 24 h post CPB. Plasma concentrations of all haemostatic proteins decreased by an average of 56% immediately following the initiation of CPB due to haemodilution. During CPB, the majority of procoagulants, inhibitors and some components of the fibrinolytic system (plasminogen, α2AP) remained stable. However, plasma concentrations of TAT and D-dimers increased during CPB showing that significant activation of the coagulation and fibrinolytic systems occurred. Mechanisms responsible for the activation of haemostasis are likely complex. However, low plasma concentrations of heparin (<2.0 units/ml in 45% of patients) during CPB were likely a major contributing etiology. ACT values showed a poor correlation (r = 0.38) with heparin concentrations likely due to concurrent haemodilution of haemostatic factors, activation of haemostatic system, hypothermia and activation of platelets. In conclusion, CPB in paediatric patients causes global decreases of components of the coagulation and fibrinolytic systems, primarily by haemodilution and secondarily by consumption.

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Viscoelastometry for detecting oral anticoagulants

Thrombosis Journal ◽

10.1186/s12959-021-00267-w ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Philipp Groene ◽

Daniela Wagner ◽

Tobias Kammerer ◽

Lars Kellert ◽

Andreas Giebl ◽

...

Keyword(s):

Healthy Volunteers ◽

Prospective Observational Study ◽

Oral Anticoagulants ◽

Plasma Concentrations ◽

Factor Xa ◽

Clotting Time ◽

Emergency Situations ◽

Tissue Plasminogen ◽

The Impact

Abstract Background Determination of anticoagulant therapy is of pronounced interest in emergency situations. However, routine tests do not provide sufficient insight. This study was performed to investigate the impact of anticoagulants on the results of viscoelastometric assays using the ClotPro device. Methods This prospective, observational study was conducted in patients receiving dabigatran, factor Xa (FXa)-inhibitors, phenprocoumon, low molecular weight heparin (LMWH) or unfractionated heparin (UFH) (local ethics committee approval number: 17–525-4). Healthy volunteers served as controls. Viscoelastometric assays were performed, including the extrinsic test (EX-test), intrinsic test (IN-test) Russel’s viper venom test (RVV-test), ecarin test (ECA-test), and the tissue plasminogen activator test (TPA-test). Results 70 patients and 10 healthy volunteers were recruited. Clotting time in the EX-test (CTEX-test) was significantly prolonged versus controls by dabigatran, FXa inhibitors and phenprocoumon. CTIN-test was prolonged by dabigatran, FXa inhibitors and UFH. Dabigatran, FXa inhibitors and UFH significantly prolonged CTRVV-test in comparison with controls (median 200, 207 and 289 vs 63 s, respectively; all p < 0.0005). Only dabigatran elicited a significant increase in CTECA-test compared to controls (median 307 vs 73 s; p < 0.0001). CTECA-test correlated strongly with dabigatran plasma concentration (measured by anti-IIa activity; r = 0.9970; p < 0.0001) and provided 100% sensitivity and 100% specificity for detecting dabigatran. Plasma concentrations (anti-XA activity) of FXa inhibitors correlated with CTRVV-test (r = 0.7998; p < 0.0001), and CTRVV-test provided 83% sensitivity and 64% specificity for detecting FXa inhibitors. Conclusions In emergency situations, ClotPro viscoelastometric assessment of whole-blood samples may help towards determining the presence and type of anticoagulant class that a patient is taking. Trial registration German clinical trials database ID: DRKS00015302.

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Detailed Quantification of Glomerular Structural Lesions Associates with Clinical Outcomes and Transcriptomic Profiles in Nephrotic Syndrome

10.1101/2021.09.16.21263706 ◽

2021 ◽

Author(s):

Jeffrey B. Hodgin ◽

Laura H. Mariani ◽

Jarcy Zee ◽

Q Liu ◽

Abigail R. Smith ◽

...

Keyword(s):

Nephrotic Syndrome ◽

Disease Progression ◽

Clinical Outcomes ◽

Messenger Rna ◽

Structural Changes ◽

Classification Systems ◽

Molecular Heterogeneity ◽

Biologically Relevant ◽

Current Classification ◽

Over Time

ABSTRACTThe current classification system for focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) does not fully capture the complex structural changes in kidney biopsies, nor the clinical and molecular heterogeneity of these diseases. The Nephrotic Syndrome Study Network (NEPTUNE) Digital Pathology Scoring System (NDPSS) was applied to 221 NEPTUNE FSGS/MCD digital kidney biopsies for glomerular scoring using 37 descriptors. The descriptor-based glomerular profiles were used to cluster patients with similar morphologic characteristics. Glomerular descriptors and patient clusters were assessed for association with time to proteinuria remission and disease progression by using adjusted Cox models, and eGFR measures over time by using linear mixed models. Messenger RNA from glomerular tissue was used to assess differentially expressed genes (DEG) between clusters and identify genes associated with individual descriptors driving cluster membership. Three clusters were identified: X (N=56), Y (N=68), and Z (N=97). Clusters Y and Z had higher probabilities of proteinuria remission (HR [95% CI]= 1.95 [0.99, 3.85] and 3.29 [1.52, 7.13], respectively), lower hazards of disease progression 0.22 [0.08, 0.57] and 0.11 [0.03, 0.45], respectively), and greater loss of eGFR over time compared with X. Cluster X had 1920 DEGs compared to Y+Z, which reflected activation of pathways of immune response and inflammation. Six individual descriptors driving the clusters individually correlated with clinical outcomes and gene expression. The NDPSS allows for characterization of FSGS/MCD patients into clinically and biologically relevant categories and uncovers histologic parameters associated with clinical outcomes and molecular signatures not included in current classification systems.TRANSLATIONAL STATEMENTFSGS and MCD are heterogeneous diseases that manifest with a variety of structural changes often not captured by conventional classification systems. This study shows that a detailed morphologic analysis and quantification of these changes allows for better representation of the structural abnormalities within each patient and for grouping patients with similar morphologic profiles into categories that are clinically and biologically relevant.

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Chromogenic anti-Xa test: the ratio between heparin activity units and concentration of apixaban and rivaroxaban

Atherothrombosis Journal ◽

10.21518/2307-1109-2020-2-96-104 ◽

2020 ◽

pp. 96-104

Author(s):

E. V. Titaeva ◽

A. B. Dobrovolsky

Keyword(s):

Oral Anticoagulants ◽

Direct Oral Anticoagulants ◽

Plasma Concentrations ◽

Factor Xa ◽

Activity Test ◽

Formation Dynamics ◽

Test Version ◽

Heparin Activity ◽

The Relationship ◽

Thrombin Formation

Introduction. The direct oral anticoagulants (DOC) therapy does not require alaboratory control; however, it may be required to determine the anticoagulationlevel to choose a treatment strategy if alarge bleeding is developing or emergency surgery is needed.The objective of this experimental study was to investigate the relationship between the residual factor Xa (FXa) activity, anti-Xa activity units oflow molecular weight heparins (LMWH), and the apixaban and rivaroxaban plasma concentrations in a chromogenic anti-Xa assay.Material and methods. Concentrated DOC solutions were prepared by extracting apixaban and rivaroxaban from crushed tablets using methanol and dimethyl sulfoxide, respectively. The resulting solutions were added to the donor plasma pool until final inhibitor concentrations are achieved in the range from 10 to 100 ng/ml plasma. Anti-Xa activity was determined using an STA-compact analyser and the Liquid anti-Xa reagent kit, an analysis protocol, and calibrators designed to control the LMWH therapy. The effect on the thrombin formation dynamics was investigated using the thrombin generation test (TGT) and the PPR reagent as a trigger (final concentrations of tissue factor are 5 pM, and those of phospholipids are 4 μM). TGT curves were analysed using the Thrombinoscope program.Results. It was shown that in the anti-Xa activity test version designed to control the LMWH therapy, there is a high correlation (R2 > 0.98) between thelogarithm of the residual factor Xa activity and the content of apixaban and rivaroxaban in the range from 10 to 80 ng/ml. Rivaroxaban shows about 1.5 times more anti-Xa activity than apixaban at equal concentrations. It was also shown that apixaban and rivaroxaban at doses equal both in concentration and in anti-Xa activity differ in their effect on the thrombin formation dynamics and thrombin inactivation in the TGT.Conclusion. In the LMWH anti-Xa activity test version, the measured range of apixaban and rivaroxaban includes 30 ng/ml and 50 ng/ ml concentrations taken as “cut-off points” to determine the treatment tactics in emergency cases. However, thelack of certified DOC calibratorslimits the use of this test in clinical practice.

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A Diagnostic Solution for Lupus Anticoagulant Testing in Patients Taking Direct Oral FXa Inhibitors Using DOAC Filter

Frontiers in Medicine ◽

10.3389/fmed.2021.683357 ◽

2021 ◽

Vol 8 ◽

Author(s):

Carine Farkh ◽

Syrine Ellouze ◽

Louis Gounelle ◽

Mama Sad Houari ◽

Jérôme Duchemin ◽

...

Keyword(s):

Lupus Anticoagulant ◽

Solid Phase ◽

Covalent Binding ◽

Plasma Concentrations ◽

Factor Xa ◽

New Device ◽

Before And After ◽

Single Use ◽

Fxa Inhibitor ◽

Inhibitor Compounds

Background: Direct oral factor Xa (FXa) inhibitors interfere with lupus anticoagulant (LA) assays challenging antiphospholipid syndrome diagnosis in treated patients. We evaluated a new device, called DOAC Filter, and its usefulness in this setting. It is a single-use filtration cartridge in which FXa inhibitor compounds are trapped by non-covalent binding while plasma is filtered through a solid phase. Patient samples were analyzed before and after filtration: 38 rivaroxaban, 41 apixaban, and 68 none. Anticoagulant plasma concentrations were measured using specific anti-Xa assays and HPLC-MS/MS. LA testing was performed using dilute Russell Viper Venom Time (dRVVT) and Silica Clotting Time (SCT). Baseline median [min–max] concentrations were 64.8 [17.6; 311.4] for rivaroxaban and 92.1 ng/mL [37.1; 390.7] for apixaban (HPLC-MS/MS). They were significantly correlated with anti-Xa assay results (r = 0.98 and r = 0.94, respectively). dRVVT was positive in 92% rivaroxaban and 72% apixaban and SCT in 28 and 41% of samples, respectively. Post-filtration, median % of neutralization was 100% with rivaroxaban and apixaban concentrations of, respectively, <2 [<2–2.4] and <2 ng/mL [<2–9.6] using HPLC-MS/MS. No significant effect of DOAC Filter was observed on LA testing in controls (n = 31) and LA-positive (n = 37) non-anticoagulated samples. dRVVT and SCT remained positive in, respectively, 16 and 8% of rivaroxaban and 41 and 18% of apixaban samples. DOAC Filter would be an easy-to-use device allowing FXa inhibitor removal from plasma samples, limiting their interference with LA testing in treated patients.

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Clinical outcomes with unfractionated heparin monitored by anti‐factor Xa vs. activated partial Thromboplastin time

American Journal of Hematology ◽

10.1002/ajh.25565 ◽

2019 ◽

Vol 94 (9) ◽

pp. 1015-1019 ◽

Cited By ~ 1

Author(s):

James C. Coons ◽

Carlo J. Iasella ◽

Megan Thornberg ◽

Mary Grace Fitzmaurice ◽

Kimberly Goehring ◽

...

Keyword(s):

Unfractionated Heparin ◽

Clinical Outcomes ◽

Partial Thromboplastin Time ◽

Factor Xa ◽

Activated Partial Thromboplastin Time

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132PD Plasma concentrations of pemetrexed to predict clinical outcomes in patients with advanced NSCLC

Journal of Thoracic Oncology ◽

10.1016/s1556-0864(18)30407-6 ◽

2018 ◽

Vol 13 (4) ◽

pp. S76-S77

Author(s):

S. Visser ◽

S. Koolen ◽

P. de Bruijn ◽

R. Mathijssen ◽

B. Stricker ◽

...

Keyword(s):

Clinical Outcomes ◽

Advanced Nsclc ◽

Plasma Concentrations

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Inhibition of thrombin generation by the zymogen factor VII: implications for the treatment of hemophilia A by factor VIIa

Blood ◽

10.1182/blood.v95.4.1330.004k28_1330_1335 ◽

2000 ◽

Vol 95 (4) ◽

pp. 1330-1335 ◽

Cited By ~ 98

Author(s):

Cornelis van 't Veer ◽

Neal J. Golden ◽

Kenneth G. Mann

Keyword(s):

Factor Viii ◽

Tissue Factor ◽

Thrombin Generation ◽

Hemophilia A ◽

Factor Viia ◽

Plasma Concentrations ◽

Factor Xa ◽

Factor Vii ◽

Lag Phase ◽

Single Chain

Factor VII circulates as a single chain inactive zymogen (10 nmol/L) and a trace (∼10-100 pmol/L) circulates as the 2-chain form, factor VIIa. Factor VII and factor VIIa were studied in a coagulation model using plasma concentrations of purified coagulation factors with reactions initiated with relipidated tissue factor (TF). Factor VII (10 nmol/L) extended the lag phase of thrombin generation initiated by 100 pmol/L factor VIIa and low TF. With the coagulation inhibitors TFPI and AT-III present, factor VII both extended the lag phase of the reaction and depressed the rate of thrombin generation. The inhibition of factor Xa generation by factor VII is consistent with its competition with factor VIIa for TF. Thrombin generation with TF concentrations >100 pmol/L was not inhibited by factor VII. At low tissue factor concentrations (<25 pmol/L) thrombin generation becomes sensitive to the absence of factor VIII. In the absence of factor VIII, factor VII significantly inhibits TF-initiated thrombin generation by 100 pmol/L factor VIIa. In this hemophilia A model, approximately 2 nmol/L factor VIIa is needed to overcome the inhibition of physiologic (10 nmol/L) factor VII. At 10 nmol/L, factor VIIa provided a thrombin generation response in the hemophilia model (0% factor VIII, 10 nmol/L factor VII) equivalent to that observed with normal plasma, (100% factor VIII, 10 nmol/L factor VII, 100 pmol/L factor VIIa). These results suggest that the therapeutic efficacy of factor VIIa in the medical treatment of hemophiliacs with inhibitors is, in part, based on overcoming the factor VII inhibitory effect.

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