DNase analysed by a novel competitive assay in patients with complications after ChAdOx1 nCoV-19 vaccination and in normal unvaccinated blood donors

Increased levels of neutrophil extracellular traps (NETs) have been detected in individuals with vaccine complications after the ChAdOx1 nCov vaccine with a correlation between the severity of vaccine side effects and the level of NETosis. DNases may disrupt NETs by degrading their content of DNA, and a balance has been reported between NETs and DNases. Because of this and since the inflammatory marker NETs may be used as a confirmatory test in diagnosing VITT, it is of interest to monitor levels of DNase in patients with increased NETs levels. The current novel rapid DNase ELISA was tested in blood samples of patients with known increased levels of NETs with or without VITT after ChAdOx1 nCoV-19 vaccination. DNase levels in VITT patients were significantly increased compared with normal unvaccinated blood donors and compared with patients with post-vaccination symptoms but not VITT. However, since EDTA was found to inhibit DNase, serum and not EDTA-plasma samples should be applied for DNase testing. The novel DNase assay may serve as a supplementary test to the NETs test when analysing samples from patients with suspected increased NETs levels.

In Vitro Apixaban Removal By CytoSorb Whole Blood Adsorber: An Experimental Study

OBJECTIVES

The use of unopposed oral anticoagulants while undergoing cardiothoracic surgery is associated with severe bleeding and increased morbidity. The aim of this experimental study was to examine if the apixaban concentration in reconstituted blood could be reduced in an in vitro setup by the use of CytoSorb whole blood adsorber, and to study how this affected global coagulation assays.

DESIGN AND SETTING

An experimental study performed in a laboratory.

PARTICIPANTS

An in vitro setup with reconstituted whole blood.

INTERVENTIONS

Reconstituted whole blood spiked with apixaban circulated in an in vitro circuit with the CytoSorb 300 mL device connected.

MEASUREMENTS AND MAIN RESULTS

Blood samples were drawn at 0, 5, 15, 30, 60, and 120 minutes of adsorption. The apixaban concentration was measured at each time point. In addition, the global coagulation assays, thromboelastometry clotting time and thrombin generation, were performed, and the results were compared with baseline values obtained before spiking blood with apixaban. After 30 minutes of adsorption, the mean apixaban concentration was reduced from 414.3 (±69.1) ng/mL to 33 (±11.4) ng/mL. Thrombin generation showed maximum effect after 60 minutes, and the thromboelastometry clotting time was close to baseline values after 120 minutes.

CONCLUSIONS

In this in vitro study, apixaban concentrations were effectively reduced, and the clotting time and thrombin generation assays were normalized by the use of CytoSorb whole blood adsorber.

Vaccine Induced Immune Thrombotic Thrombocytopenia Causing a Severe Form of Cerebral Venous Thrombosis With High Fatality Rate: A Case Series

During a 2-week period, we have encountered five cases presenting with the combination of cerebral venous thrombosis (CVT), intracerebral hemorrhage and thrombocytopenia. A clinical hallmark was the rapid and severe progression of disease in spite of maximum treatment efforts, resulting in fatal outcome in for 4 out of 5 patients. All cases had received ChAdOx1 nCov-19 vaccine 1–2 weeks earlier and developed a characteristic syndrome thereafter. The rapid progressive clinical course and high fatality rate of CVT in combination with thrombocytopenia in such a cluster and in otherwise healthy adults is a recent phenomenon. Cerebral autopsy findings were those of venous hemorrhagic infarctions and thrombi in dural venous sinuses, including thrombus material apparently rich in thrombocytes, leukocytes and fibrin. Vessel walls were free of inflammation. Extra-cerebral manifestations included leech-like thrombi in large veins, fibrin clots in small venules and scattered hemorrhages on skin and membranes. CVT with thrombocytopenia after adenovirus vectored COVID-19 vaccination is a new clinical syndrome that needs to be recognized by clinicians, is challenging to treat and seems associated with a high mortality rate.

The effect of emicizumab and bypassing agents in patients with hemophilia - An in vitro study

BACKGROUND

Emicizumab is a nonfactor replacement therapy for hemophilia A (HA) and is a bispecific monoclonal antibody mimicking factor VIII by binding both factors IXa and X. Although it reduces the frequency of bleeding episodes, there is still need for bypassing agents in case of breakthrough bleeds or need for surgery. The HAVEN-1 study showed an increased risk of thrombotic events and episodes of thrombotic microangiopathic hemolytic anemia with simultaneous treatment with emicizumab and activated prothrombin complex concentrate (aPCC) in high doses (>100 U/kg daily) for more than 1 day, and it is suspected that these drugs have a synergistic hemostatic effect.

OBJECTIVES

To evaluate and compare the hemostatic effect of bypassing agents in vitro in people with HA before and after starting treatment with emicizumab to investigate if dosing should be adjusted to optimize treatment.

PATIENTS/METHODS

Blood collected before and after start of treatment with emicizumab was spiked with aPCC and recombinant factor VIIa (rFVIIa) at different concentrations. The effect of aPCC and rFVIIa was assessed by thrombin generation assay and thromboelastometry.

RESULTS

Six people with HA were included. The response to aPCC in thrombin generation after starting emicizumab was significantly stronger than before. This synergistic effect was less pronounced for emicizumab and rFVIIa. Furthermore, aPCC shortened thromboelastometry clotting time more effectively after starting emicizumab than before starting this treatment.

CONCLUSIONS

We demonstrated a strong synergistic effect of emicizumab and aPCC and a similar but less pronounced effect of rFVIIa in people treated with emicizumab.

Investigation of the Optimal Dose aPCC in Reversing the Effect of Factor Xa Inhibitors-An In Vitro Study

Factor (F) Xa inhibitors are safe and effective alternatives to warfarin. There are concerns about the lack of a reversal strategy in case of serious bleeds or need for emergency surgery in situations when the antidote andexanet alfa is not available. Factor concentrates are widely used, but there are few clinical studies regarding the reversal effect of activated prothrombin complex concentrate (aPCC). Because of the feared thrombogenicity, administration of the lowest effective dose would be desirable. To determine the lowest concentration of aPCC sufficient to reverse the effect of rivaroxaban and apixaban. Blood from 18 healthy volunteers were supplemented with apixaban or rivaroxaban. aPCC was added to obtain 10 different concentrations ranging from 0.08-1.60 U/mL. Thromboelastometry and thrombin generation assay were used to assess the reversal effect. aPCC concentrations of 0.08 and 0.16 U/mL restored thromboelastometry clotting time to baseline in apixaban (P = 1.0) and rivaroxaban (P = 1.0)-containing samples, respectively. The concentrations 0.08 U/mL (P = 0.5) and 0.24 U/mL (P = 0.2) were sufficient to restore thrombin generation. Concentrations of 0.56 U/mL and higher, caused significantly higher ETP than baseline in apixaban-containing samples (P < 0.05). aPCC concentrations lower than previously reported were effective in reversing the effect of FXa inhibitors in vitro.

The impact of rivaroxaban on primary hemostasis in patients with venous thrombosis

Factor Xa inhibitors are safe and effective alternatives to warfarin, but several studies indicate that rivaroxaban may cause a different risk profile for bleeding. For instance, while the risk of major bleeding in general may be lower with rivaroxaban than for warfarin, the risk of gastrointestinal bleeding or abnormal uterine bleeding may be higher. The underlying mechanisms for these differences are not known, and the effect of rivaroxaban on primary hemostasis is poorly understood. The aim of this study was to investigate the effect of rivaroxaban on platelet function, P-selectin and von Willebrand factor (VWF) antigen and activity. Patients with venous thrombosis assigned to 3 months of treatment due to temporary risk factors were included. Blood was collected both during (on-treatment) and 4-6 weeks after end of treatment (without treatment). The platelet reactivity was assessed by light transmission aggregometry. P-selectin was measured by an enzyme-linked immunosorbent assay and vWF antigen and activity by latex immunoagglutination assays. Platelet reactivity during on-treatment (trough- and peak concentration) was similar to values without treatment. There was a trend toward a reduction of P-selectin during rivaroxaban treatment (peak concentration) compared to value without treatment (p = 0.06). There were no differences in vWF antigen and activity between the different time-points. We found no difference in platelet reactivity or vWF antigen/activity during rivaroxaban treatment compared with values without treatment. Apart from possibly causing a reduction of P-selectin, rivaroxaban seems not to influence primary hemostasis.

Activated prothrombin complex concentrate to reverse the factor Xa inhibitor (apixaban) effect before emergency surgery: a case series

BACKGROUND

The lack of an antidote against factor Xa inhibitors in case of major bleeding or need for urgent surgery is a concern to clinicians. Guidelines on managing major bleeding in patients under anticoagulation with a factor Xa inhibitor suggest several hemostatic agents to reverse the effect, but there is no consensus regarding the choice of drug or appropriate dose. The ability of prothrombin complex concentrate, activated prothrombin complex concentrate, and recombinant factor VIIa to reverse the effect of factor Xa inhibitors has been evaluated in animal studies, in vitro studies, and healthy volunteers, but not yet in randomized clinical studies.

CASE PRESENTATION

We report a consecutive case series of patients under factor Xa inhibitor (apixaban) treatment who received activated prothrombin complex concentrate to reverse the anticoagulation effect before emergency cardiovascular surgery. Patient 1, a 63-year-old white man, was operated with replacement of the aortic valve; patient 2, a 65-year-old white man, underwent heart transplantation; patient 3, a 68-year-old white man, was operated for acute type A aortic dissection. They all received activated prothrombin complex concentrate 25 IU/kg immediately before surgery. In two of the cases, the global coagulation assay thromboelastometry (ROTEM™) was performed before and after administering activated prothrombin complex concentrate. The ROTEM™ clotting time was reduced from 1900 seconds to 740 seconds and from 1482 to 807 seconds, respectively, after administering a dose of 25 IU/kg activated prothrombin complex concentrate. The apixaban concentration before reversal was within the range considered to be the therapeutic level in all cases. No bleeding complications occurred during surgery, but one case was complicated with bleeding postoperatively. No thromboembolic complications were observed during or after surgery.

CONCLUSIONS

Activated prothrombin complex concentrate 25 IU/kg reversed the anticoagulation effect of apixaban effectively and safely before emergency cardiovascular surgery.

The reversal effect of prothrombin complex concentrate (PCC), activated PCC and recombinant activated factor VII against anticoagulation of Xa inhibitor

Background

An increasing number of patients are treated with direct-acting oral anticoagulants (DOACs), but the optimal way to reverse the anticoagulant effect is not known. Specific antidotes are not available and prothrombin complex concentrate (PCC), activated PCC (aPCC) and recombinant factor VIIa (rFVIIa) are variously used as reversal agents in case of a major bleeding. We aimed to determine the most effective haemostatic agent and dose to reverse the effect of rivaroxaban in blood samples from patients taking rivaroxaban for therapeutic reasons.

Methods

Blood samples from rivaroxaban-treated patients (n = 50) were spiked with PCC, aPCC and rFVIIa at concentrations imitating 80%, 100% and 125% of suggested therapeutic doses. The reversal effect was assessed by thromboelastometry in whole blood and a thrombin generation assay (TGA) in platelet-poor plasma. Samples from healthy subjects (n = 40) were included as controls.

Results

In thromboelastometry measurements, aPCC and rFVIIa had a superior effect to PCC in reversing the rivaroxaban-induced lenghtening of clotting time (CT). aPCC was the only haemostatic agent that shortened the CT down to below the control level. Compared to healthy controls, patients on rivaroxaban also had a prolonged lag time and decreased peak concentration, velocity index and endogenous thrombin potential (ETP) in platelet-poor plasma. aPCC reversed these parameters more effectively than rFVIIa and PCC. There were no differences in efficacy between 80%, 100% and 125% doses of aPCC.

Conclusions

aPCC seems to reverse the anticoagulant effect of rivaroxaban more effectively than rFVIIa and PCC by evaluation with thromboelastometry and TGA in vitro.