Factor XII deficiency evaluated by thrombin generation assay

Abstract During surface-initiated blood coagulation in vitro, activated factor XII (fXIIa) converts factor XI (fXI) to fXIa. Whereas fXI deficiency is associated with a hemorrhagic disorder, factor XII deficiency is not, suggesting that fXI can be activated by other mechanisms in vivo. Thrombin activates fXI, and several studies suggest that fXI promotes coagulation independent of fXII. However, a recent study failed to find evidence for fXII-independent activation of fXI in plasma. Using plasma in which fXII is either inhibited or absent, we show that fXI contributes to plasma thrombin generation when coagulation is initiated with low concentrations of tissue factor, factor Xa, or α-thrombin. The results could not be accounted for by fXIa contamination of the plasma systems. Replacing fXI with recombinant fXI that activates factor IX poorly, or fXI that is activated poorly by thrombin, reduced thrombin generation. An antibody that blocks fXIa activation of factor IX reduced thrombin generation; however, an antibody that specifically interferes with fXI activation by fXIIa did not. The results support a model in which fXI is activated by thrombin or another protease generated early in coagulation, with the resulting fXIa contributing to sustained thrombin generation through activation of factor IX.

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Factor XII Deficiency in ECMO Patients

Blood ◽

10.1182/blood-2019-131614 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4965-4965 ◽

Cited By ~ 1

Author(s):

Katherine Regling ◽

Sarah Ramiz ◽

Meera B. Chitlur

Keyword(s):

Board Of Directors ◽

Thrombin Generation ◽

Ecmo Support ◽

Factor Xii ◽

Advisory Committees ◽

Factor Xii Deficiency ◽

Coagulation Assays ◽

Factor Deficiency ◽

Thrombotic Complications ◽

Thromb Thrombolysis

Background: Extracorporeal membrane oxygenation (ECMO) for cardiopulmonary support of critically ill patients is used frequently in the pediatric and adult population. Although a lifesaving modality, it is burdened with high morbidity and mortality as a result of hematologic complications (Dalton, et al. Am J Respir Crit Care Med. 2017). Bleeding and thrombosis are related to contact of blood and its cellular components with the non-biologic surface of the extracorporeal circuit used that results in a massive inflammatory and clotting response. Factor XII deficiency is not associated with bleeding, but results in a significant prolongation of conventional coagulation assays making them unreliable for monitoring. Here we discuss 3 cases of Factor XII deficiency and the implications it has on monitoring anticoagulation in patients on ECMO. Laboratory characteristics for all 3 patients are outlined in Table 1. Case 1: Newborn full-term male with persistent pulmonary hypertension (PPHN) and meconium aspiration syndrome (MAS) with respiratory failure was placed on ECMO support on day of life 1. Patient received several units of cryoprecipitate and fresh frozen plasma (FFP) to correct deficiencies throughout his 31 day ECMO course. Patient did not have any bleeding or thrombotic complications, however he showed no improvement in lung function and decision was made to discontinue ECMO support. Case 2: Newborn full-term male with severe hypoxic ischemic encephalopathy (HIE) and MAS with secondary PPHN required ECMO support on day of life 1. His Factor XII level normalized with replacement by FFP and was decannulated after 11 days of ECMO support. This patient was discharged home with family in stable condition at 5 weeks of age. Case 3: 20-year-old female with history of recurrent astrocytoma, chronic lung disease, hydrocephalus with ventriculoperitoneal (VP) shunt, and tracheostomy presented with multifocal pneumonia and suspected sepsis. Despite fluid resuscitation and ventilatory management patient continued to have hypotension and hypoxia and thus was placed on ECMO. Prior to cannulation, patient was noted to have a coagulopathy. In addition, Factor II was low at 57% and corrected with one unit of FFP; which was thought to be related to consumptive process. On ECMO day 8, she had worsening hypotension despite vasopressor support and fixed and dilated pupils; suspected to have thromboembolic stroke and thus decision was made to withdraw life support. Discussion: Adequate anticoagulation in patients with Factor XII deficiency requiring ECMO support presents a challenging task. Patients with Factor XII deficiency generally do not show symptoms of a bleeding disorder, which may lead to misinterpretation of coagulation assays (Kokoye, et al. Thromb Res 2016). Increased contact activation inside the ECMO cannula causes activation of platelets, consumption of Factor XII, and formation of FXIIa-antithrombin complexes that may contribute to increased risk for thrombus formation (Kokoye, et al. Thromb Res 2016 and Bachler, et al. J Thromb Thrombolysis 2019). All patients had Factor XII levels <40% on initial testing, which is sufficient to cause severe changes to the aPTT. A circulating anticoagulant aPTT was completed to assess for presence of lupus anticoagulants in 2 of the patients, which has been known to falsely elevate the aPTT and was negative (Bachler, et al. J Thromb Thrombolysis 2019). All patients received FFP in an attempt to correct deficiency and facilitate the use of aPTT and ACTs for monitoring. However, this did not prove to be successful in 2/3 patients despite receiving adult plasma. Hepzyme TEGs showed improvement in R-time post-FFP in 2 patients, but in 1 there remained evidence of factor deficiency. It is clear that traditional coagulation assays, including aPTT and ACT, become unreliable and the R-time on TEG becomes difficult to dissect heparin versus coagulation factor effect. We recommend attempting to correct factor deficiency with FFP to potentially decrease risk of thrombotic complications, and choosing an alternative laboratory monitoring assay for heparin, such as Anti-Xa levels, which may more accurately correspond to the anticoagulation status in this population. Currently, we are running a modified thrombin generation assay in these Factor XII deficient patients, pre/post-FFP, to identify if there is a decrease in thrombin generation post-FXII/FFP supplementation. Table 1 Disclosures Chitlur: Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda/Shire: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bioveritiv/Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; CSL-Behring: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Research Funding; Octapharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novo Nordisk Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees.

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Inhibition of Thrombin Generation in Plasma by Inhibitors of Factor Xa

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657717 ◽

1997 ◽

Vol 78 (04) ◽

pp. 1215-1220 ◽

Cited By ~ 25

Author(s):

D Prasa ◽

L Svendsen ◽

J Stürzebecher

Keyword(s):

Thrombin Generation ◽

Factor Xa ◽

Thrombin Inhibitors ◽

Thrombin Inhibitor ◽

Thrombin Generation Assay ◽

Ic50 Values ◽

Fxa Inhibitor ◽

20 Nm ◽

Tick Anticoagulant Peptide ◽

Inhibition Of Thrombin

SummaryA series of inhibitors of factor Xa (FXa) were investigated using the thrombin generation assay to evaluate the potency and specificity needed to efficiently block thrombin generation in activated human plasma. By inhibiting FXa the generation of thrombin in plasma is delayed and decreased. Inhibitor concentrations which cause 50 percent inhibition of thrombin generation (IC50) correlate in principle with the Ki values for inhibition of free FXa. Recombinant tick anticoagulant peptide (r-TAP) is able to inhibit thrombin generation with considerably low IC50 values of 49 nM and 37 nM for extrinsic and intrinsic activation, respectively. However, the potent synthetic, low molecular weight inhibitors of FXa (Ki values of about 20 nM) are less effective in inhibiting the generation of thrombin with IC50 values at micromolar concentrations.The overall effect of inhibitors of FXa in the thrombin generation assay was compared to that of thrombin inhibitors. On the basis of similar Ki values for the inhibition of the respective enzyme, synthetic FXa inhibitors are less effective than thrombin inhibitors. In contrast, the highly potent FXa inhibitor r-TAP causes a stronger reduction of the thrombin activity in plasma than the most potent thrombin inhibitor hirudin.

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A Case of Bladder Tamponade with Factor XII Deficiency in a Cat

Japanese Journal of Veterinary Anesthesia & Surgery ◽

10.2327/jvas.45.13 ◽

2014 ◽

Vol 45 (1) ◽

pp. 13-18

Author(s):

Harumichi ITOH ◽

Tomoya HARAGUCHI ◽

Kazuhito ITAMOTO ◽

Kinya TAMURA ◽

Satoshi KANBAYASHI ◽

...

Keyword(s):

Factor Xii ◽

Factor Xii Deficiency

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A rare case of not-so-benign factor XII deficiency

European Journal of Medical Case Reports ◽

10.24911/ejmcr/173-1532134733 ◽

2019 ◽

pp. 1-4

Author(s):

Adeel Arshad ◽

Nazia Mohamed ◽

Absia Jabbar ◽

Makiko Ban-hoefen

Keyword(s):

Rare Case ◽

Factor Xii ◽

Factor Xii Deficiency

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Concizumab, an anti-tissue factor pathway inhibitor antibody, induces increased thrombin generation in plasma from haemophilia patients and healthy subjects measured by the thrombin generation assay

Haemophilia ◽

10.1111/hae.13260 ◽

2017 ◽

Vol 23 (5) ◽

pp. 769-776 ◽

Cited By ~ 40

Author(s):

E. K. Waters ◽

J. Sigh ◽

U. Friedrich ◽

I. Hilden ◽

B. B. Sørensen

Keyword(s):

Tissue Factor ◽

Healthy Subjects ◽

Thrombin Generation ◽

Tissue Factor Pathway Inhibitor ◽

Thrombin Generation Assay ◽

Tissue Factor Pathway

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Contact system activation and high thrombin generation in hyperthyroidism

Acta Endocrinologica ◽

10.1530/eje-16-0835 ◽

2017 ◽

Vol 176 (5) ◽

pp. 583-589 ◽

Cited By ~ 2

Author(s):

Namhee Kim ◽

Ja-Yoon Gu ◽

Hyun Ju Yoo ◽

Se Eun Han ◽

Young Il Kim ◽

...

Keyword(s):

Neutrophil Elastase ◽

Thrombin Generation ◽

Contact System ◽

Factor Vii ◽

Factor Xii ◽

Free T4 ◽

Thrombotic Risk ◽

Double Stranded Dna ◽

System Activation ◽

Normal Controls

BackgroundHyperthyroidism is associated with increased thrombotic risk. As contact system activation through formation of neutrophil extracellular traps (NET) has emerged as an important trigger of thrombosis, we hypothesized that the contact system is activated along with active NET formation in hyperthyroidism and that their markers correlate with disease severity.Subjects and methodsIn 61 patients with hyperthyroidism and 40 normal controls, the levels of coagulation factors (fibrinogen, and factor VII, VIII, IX, XI and XII),D-dimer, thrombin generation assay (TGA) markers, NET formation markers (histone–DNA complex, double-stranded DNA and neutrophil elastase) and contact system markers (activated factor XII (XIIa), high-molecular-weight kininogen (HMWK), prekallikrein and bradykinin) were measured.ResultsPatients with hyperthyroidism showed higher levels of fibrinogen (median (interquartile range), 315 (280–344) vs 262 (223–300),P = 0.001),D-dimer (103.8 (64.8–151.5) vs 50.7 (37.4–76.0),P < 0.001), peak thrombin (131.9 (102.2–159.4) vs 31.6 (14.8–83.7),P < 0.001) and endogenous thrombin potential (649 (538–736) vs 367 (197–1147),P = 0.021) in TGA with 1 pM tissue factor, neutrophil elastase (1.10 (0.39–2.18) vs 0.23 (0.20–0.35),P < 0.001), factor XIIa (66.9 (52.8–87.0) vs 73.0 (57.1–86.6),P < 0.001), HMWK (6.11 (4.95–7.98) vs 3.83 (2.60–5.68),P < 0.001), prekallikrein (2.15 (1.00–6.36) vs 1.41 (0.63–2.22),P = 0.026) and bradykinin (152.4 (137.6–180.4) vs 118.3 (97.1–137.9),P < 0.001) than did normal controls. In age- and sex-adjusted logistic regression analysis, fibrinogen, factor VIII, IX and XIIa,D-dimer, peak thrombin, neutrophil elastase, HMWK and bradykinin showed significant odds ratios representing hyperthyroidism’s contribution to coagulation and contact system activation. Free T4 was significantly correlated with factors VIII and IX,D-dimer, double-stranded DNA and bradykinin.ConclusionThis study demonstrated that contact system activation and abundant NET formation occurred in the high thrombin generation state in hyperthyroidism and were correlated with free T4 level.

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