Antithrombin Levels and Heparin Responsiveness during Venoarterial Extracorporeal Membrane Oxygenation: A Prospective Single-center Cohort Study

BACKGROUND

Unfractionated heparin, administered during venoarterial extracorporeal membrane oxygenation to prevent thromboembolic events, largely depends on plasma antithrombin for its antithrombotic effects. Decreased heparin responsiveness seems frequent on extracorporeal membrane oxygenation; however, its association with acquired antithrombin deficiency is poorly understood. The objective of this study was to describe longitudinal changes in plasma antithrombin levels during extracorporeal membrane oxygenation support and evaluate the association between antithrombin levels and heparin responsiveness. The hypothesis was that extracorporeal membrane oxygenation support would be associated with acquired antithrombin deficiency and related decreased heparin responsiveness.

METHODS

Adults receiving venoarterial extracorporeal membrane oxygenation were prospectively included. All patients received continuous intravenous unfractionated heparin using a standardized protocol (target anti-Xa 0.3 to 0.5 IU/ml). For each patient, arterial blood was withdrawn into citrate-containing tubes at 11 time points (from hour 0 up to day 7). Anti-Xa (without dextran or antithrombin added) and antithrombin levels were measured. The primary outcome was the antithrombin plasma level. In the absence of consensus, antithrombin deficiency was defined as a time-weighted average of antithrombin less than or equal to 70%. Data regarding clinical management and heparin dosage were collected.

RESULTS

Fifty patients, including 42% postcardiotomy, were included between April 2020 and May 2021, with a total of 447 samples. Median extracorporeal membrane oxygenation duration was 7 (interquartile range, 4 to 12) days. Median antithrombin level was 48% (37 to 60%) at baseline. Antithrombin levels significantly increased throughout the follow-up. Time-weighted average of antithrombin levels was 63% (57 to 73%) and was less than or equal to 70% in 32 (64%) of patients. Overall, 45 (90%) patients had at least one antithrombin value less than 70%, and 35 (70%) had at least one antithrombin value less than 50%. Antithrombin levels were not significantly associated with heparin responsiveness evaluated by anti-Xa assay or heparin dosage.

CONCLUSIONS

Venoarterial extracorporeal membrane oxygenation support was associated with a moderate acquired antithrombin deficiency, mainly during the first 72 h, that did not correlate with heparin responsiveness.

EDITOR’S PERSPECTIVE

Thrombin Generation Assay in Antiphospholipid Antibodies Positive Subjects as a Personalized Thrombotic Risk Assessment: State of the Art and Perspectives

PURPOSE OF THE REVIEW

Thrombotic risk assessment in antiphospholipid positive (aPL +) subjects is a major challenge, and the study of in vitro thrombin generation (thrombin generation assays (TGA)) could provide useful information. Activated protein C (APC) sensitivity is involved in thrombotic events in antiphospholipid syndrome patients. We summarized methods used to assess APC sensitivity with TGA and evaluated the prognostic role of APC resistance through literature search.

RECENT FINDINGS

APC resistance induced by aPL is a complex pathway. Several cross-sectional studies assessed APC sensitivity to understand thrombotic event mechanisms in aPL + subjects. Only one prospective cohort had investigated the prognostic impact of APC resistance in aPL + subjects, with a positive and significant correlation between APC sensitivity and the risk of thrombosis during the follow up (hazard ratio, 6.07 [95% CI, 1.69-21.87]). APC resistance assessed with TGA could be associated with thrombotic events in aPL + subjects.

Prothrombin conversion and thrombin decay in patients with cirrhosis-role of prothrombin and antithrombin deficiencies

BACKGROUND

Thrombin generation (TG) in the presence of thrombomodulin (TG-TM) in the plasma of patients with cirrhosis (PWC) is tilted toward a hypercoagulable phenotype. Low protein C and elevated factor VIII levels play a role, but other determinants, such as the prothrombin/antithrombin pair, must also be studied.

OBJECTIVES

The objectives were (i) to quantitatively assess the subprocesses (prothrombin conversion and thrombin decay) and (ii) to understand the underlying mechanism by studying TG dynamics after prothrombin and antithrombin plasma level correction in PWC.

METHODS

We studied TG-TM in plasma samples of 36 healthy controls (HCs) and 41 PWC with prothrombin and antithrombin levels of <70% and after their correction. We initiated coagulation with an intermediate picomolar concentration of tissue factor. We determined the overall thrombin potential, prothrombin conversion, and thrombin decay.

RESULTS

TG-TM was increased in PWC compared with HC due to impaired thrombin inhibition. Indeed, thrombin decay capacity (min-1) decreased from 0.37 (0.35-0.40) in HC to 0.33 (0.30-0.37) in the Child-Turcotte-Pugh A (CTP-A; P = .09), 0.27 (0.26-0.30) in the CTP-B (P < .001), and 0.20 (0.19-0.20) in the CTP-C (P < .001) group. Concomitant correction of prothrombin and antithrombin increased endogenous thrombin potential with prothrombin conversion surpassing thrombin decay. By contrast, when we corrected only antithrombin, TG-TM was normalized and even consistent with a hypocoagulable phenotype in the CTP-C group.

CONCLUSION

Our results highlight that in PWC, hypercoagulability (evidenced in the presence of TM) is due to impaired thrombin decay, whereas low prothrombin levels do not translate into decreased prothrombin conversion, likely due to altered TM-activated protein C negative feedback.

Laboratory Monitoring of Heparin Anticoagulation in Hemodialysis: Rationale and Strategies

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are commonly used to prevent clotting of the hemodialysis extracorporeal circuit and optimize hemodialysis adequacy. There is no consensus on the optimal dosing for UFH and LMWHs during hemodialysis. In clinical practice, semiquantitative clotting scoring of the dialyzer and venous chamber may help to guide UFH and LMWH dose adjustment. Laboratory monitoring has not been shown to improve clinical outcomes and is therefore not routinely indicated in most hemodialysis patients. It might, however, be considered in select patients, such as those with extremes of body weight or history of repeated clotting or bleeding. Methods for laboratory monitoring include the activated partial thromboplastin time, activated clotting time, and antifactor Xa assays for UFH and antifactor Xa assay for LMWHs. Target ranges for anticoagulation in hemodialysis have been suggested but not clearly defined. When utilizing these tests, issues such as availability, standardization, interfering factors, and interpretation must be considered. In this narrative review, we discuss the rationale and methods of monitoring anticoagulation in hemodialysis.

Venous thromboembolism prophylaxis and multiple myeloma patients in real-life: Results of a large survey and clinical guidance recommendations from the IFM group

Venous thromboembolism (VTE) remains a critical issue in the management of patients with multiple myeloma (MM), particularly when immunomodulatory drugs (IMiDs) combined with dexamethasone therapy are being prescribed as first-line and relapse therapy. One possible explanation for the persistent high rates of VTE, is the use of inappropriate thromboprophylaxis strategies for patients starting antimyeloma treatment. To tackle the issue, the Intergroupe francophone du myélome (IFM) offered convenient guidance for VTE thromboprophylaxis in MM patients initiating systemic therapy. This guidance is mainly supported by the results of a large survey on the clinical habits regarding VTE of physicians who are substantially involved in daily care of MM patients. VTE prophylaxis should be considered for all patients treated with IMiDs in combination with dexamethasone, in the absence of significant comorbidities, such as renal failure or bleeding risk. Anticoagulant should be preferred to antiplatelet agents for thromboprophylaxis. Despite the absence of large randomized controlled trials comparing those attitudes/options, available data on direct oral anticoagulants, which are already used in daily management of MM patients, are consistent with their potential usefulness for VTE prophylaxis in such patients. However, in order to implement a personalized continuous improvement strategy, clinicians must to be organized to collect all the data regarding this management. In other situations, thromboprophylaxis should be evaluated by using risk models and after careful evaluation of the risk/benefit ratio.

Factors Influencing Anti-Xa Assays: A Multicenter Prospective Study in Critically Ill and Noncritically Ill Patients Receiving Unfractionated Heparin

BACKGROUND

 The presence of dextran sulfate (DS) in reagents and the type of blood collection tube (citrate/citrated-theophylline-adenosine-dipyridamole [CTAD]) can lead to discrepancies between unfractionated heparin (UFH) anti-Xa levels.

OBJECTIVES

 To evaluate the extent of the effect (1) of different reagents containing or not containing DS and (2) of the blood collection tubes, on UFH anti-Xa levels, in various clinical situations (NCT04700670).

METHODS

 We prospectively included patients from eight centers: group (G)1, cardiopulmonary bypass (CPB) after heparin neutralization (n = 39); G2, cardiothoracic intensive care unit (ICU) after CPB (n = 35); G3, medical ICU (n = 53); G4, other medical inpatients (n = 38). Blood was collected into citrated and CTAD tubes. Chromogenic anti-Xa assays were centrally performed, using seven reagent/analyzer combinations including two without DS. The association between anti-Xa levels and covariates was tested using a linear mixed-effects model.

RESULTS

 We analyzed 4,546 anti-Xa values from 165 patients. Median anti-Xa levels were systematically higher with reagents containing DS, whatever the patient group, with the greatest effect observed in G1 (0.32 vs. 0.05 IU/mL). Anti-Xa levels were slightly higher in CTAD than in citrate samples, irrespective of the assay. The model showed: (1) a significant dextran-patient group interaction (p < 0.0001), the effect of DS on anti-Xa levels varying from 30.9% in G4 to 296% in G1, and (2) a significant effect of CTAD, varying between patient groups (p = 0.0302).

CONCLUSION

 The variability of anti-Xa levels with a great overestimation of the values, using a reagent containing DS, can lead to different treatment decisions, especially after heparin neutralization by protamine. Clinical consequences of these differences remain to be demonstrated.

Reassessment of dextran sulfate in anti-Xa assay for unfractionated heparin laboratory monitoring

Background

Anti-Xa assays are used for unfractionated heparin (UFH) monitoring. Dextran sulfate (DS) is used in some assays to overcome the artifactual preanalytical release of platelet factor 4. However, the practical implications of this test modification have not been studied extensively.

Objectives

To investigate the impact of the presence of DS in the anti-Xa assay for UFH laboratory monitoring.

Methods

We studied factor Xa inhibition, using an assay without DS (Stago Liquid Anti-Xa), in normal pool plasma spiked with various concentrations of UFH (up to 1 IU/mL) in the presence of increasing concentrations of DS (up to 2560 μg/mL). We also investigated the effect of DS on FXa inhibition measured after the addition of UFH and heparin antagonists (protamine and Polybrene; Sigma Aldrich). Eventually, we compared the anti-Xa levels measured using the assay without DS to those measured with an assay containing DS (BIOPHEN Heparin LRT, Hyphen BioMed).

Results

DS per se had a detectable anti-Xa effect. FXa inhibition in UFH-spiked plasma linearly increased with increasing concentrations of added DS, with a plateau at approximately 160 μg/mL DS, at which the apparent anti-Xa level had almost doubled. In the presence of heparin antagonists, the addition of DS increased anti-Xa levels, corresponding to the dissociation of the UFH-antagonists complexes in vitro. With the anti-Xa assay containing DS, UFH inhibition was not detected.

Conclusion

In the presence of high concentrations of DS, FXa inhibition was much higher than that predicted from added UFH amounts, presumably related to the greater availability of UFH for interaction with antithrombin. While the relevance of measuring this "masked" heparin has not been demonstrated, the presence of DS renders the result inaccurate in the presence of protamine or Polybrene.

How to assess hypercoagulability in heparin-induced thrombocytopenia? Biomarkers of potential value to support therapeutic intensity of non-heparin anticoagulation

BACKGROUND

In case of heparin-induced thrombocytopenia (HIT), the switch to a non-heparin anticoagulant is mandatory, at a therapeutic dose. Such a treatment has limitations though, especially for patients with renal and/or hepatic failure. Candidate laboratory tests could detect the more coagulable HIT patients, for whom therapeutic anticoagulation would be the more justified.

PATIENTS AND METHODS

This was a monocentre observational prospective study in which 111 patients with suspected HIT were included. Nineteen were diagnosed with HIT (ELISA and platelet activation assay), among whom 10 were classified as HITT + when a thrombotic event was present at diagnosis or during the first following week. Two plasma prethrombotic biomarkers of in vivo activation of the haemostasis system, procoagulant phospholipids (ProcoagPPL) associated with extracellular vesicles and fibrin monomers (FM test), as well as in vitro thrombin potential (ST Genesia; low picomolar tissue factor) after heparin neutralization (heparinase), were studied. The results were primarily compared between HITT + and HITT- patients.

RESULTS

Those HIT + patients with thrombotic events in acute phase or shortly after (referred as HITT+) had a more coagulable phenotype than HIT + patients without thrombotic events since: (i) clotting times related to plasma procoagulant phospholipids tended to be shorter; (ii) fibrin monomers levels were statistically significantly higher (p = 0.0483); (iii) thrombin potential values were statistically significantly higher (p = 0.0404). Of note, among all patients suspected of suffering from HIT, we did not evidence a hypercoagulable phenotype in patients diagnosed with HIT compared to patients for whom the diagnosis of HIT was ruled out.

CONCLUSION

The three tests could help identify those HIT patients the most prone to thrombosis.

Variability among commercial batches of normal pooled plasma in lupus anticoagulant testing

INTRODUCTION

Lupus anticoagulant (LA) testing requires normal pooled plasma (NPP) in performing mixing studies and can be used for normalized ratios of clotting times (CTs). The aims were to demonstrate whether significant differences in clotting times between two batches of a same commercial NPP (CRYOcheck™) directly affect NPP-based cut-off values.

METHODS

Diluted Russell Viper venom time (DRVVT) and activated partial thromboplastin time (aPTT) were used for LA testing. Screening, mixing and confirm tests were performed with Stago® instruments and reagents. Two batches of commercial NPP (A1291 and A1301 from CRYOcheck™; frozen) were compared in the determination of cut-off values. Cut-off values were defined as 99th percentile values of 60 healthy donors and compared with Mann-Whitney U test.

RESULTS

Cut-off values obtained with the two NPP batches were significantly different for DRVVT (screen normalized ratio: 1.09 vs. 1.24, screen mix: 41.9 s vs. 38.9 s; index of circulating anticoagulant: 5.0 vs. 8.4; all had p-value <.001). On the contrary, no significant differences were observed for aPTT (screen normalized ratio: 1.32 vs. 1.34; p-value = .4068, screen mix: 37.8 s vs. 38.1 s; p-value = .1153) except for index of circulating anticoagulant: 9.6 versus 10.4 (p-value <.05).

CONCLUSION

This study demonstrates that differences between two commercial NPP batches produced by a same manufacturer influenced LA cut-off values used for mixing studies and normalized ratios. Adequate cut-off setting, taking into account NPP CTs, is important to provide accurate conclusion about the presence or absence of a LA and avoid potential clinical impact.

Assessment of DOAC in GEriatrics (Adage Study): Rivaroxaban/Apixaban Concentrations and Thrombin Generation Profiles in NVAF Very Elderly Patients

BACKGROUND

 Although a growing number of very elderly patients with atrial fibrillation (AF), multiple conditions, and polypharmacy receive direct oral anticoagulants (DOACs), few studies specifically investigated both apixaban/rivaroxaban pharmacokinetics and pharmacodynamics in such patients.

AIMS

 To investigate: (1) DOAC concentration-time profiles; (2) thrombin generation (TG); and (3) clinical outcomes 6 months after inclusion in very elderly AF in-patients receiving rivaroxaban or apixaban.

METHODS

 Adage-NCT02464488 was an academic prospective exploratory multicenter study, enrolling AF in-patients aged ≥80 years, receiving DOAC for at least 4 days. Each patient had one to five blood samples at different time points over 20 days. DOAC concentrations were determined using chromogenic assays. TG was investigated using ST-Genesia (STG-ThromboScreen, STG-DrugScreen).

RESULTS

 We included 215 patients (women 71.1%, mean age: 87 ± 4 years), 104 rivaroxaban and 111 apixaban, and 79.5% receiving reduced-dose regimen. We observed important inter-individual variabilities (coefficient of variation) whatever the regimen, at C _max [49-46%] and C _min [75-61%] in 15 mg rivaroxaban and 2.5 mg apixaban patients, respectively. The dose regimen was associated with C _max and C _min plasma concentrations in apixaban (p = 0.0058 and p = 0.0222, respectively), but not in rivaroxaban samples (multivariate analysis). Moreover, substantial variability of thrombin peak height (STG-ThromboScreen) was noticed at a given plasma concentration for both xabans, suggesting an impact of the underlying coagulation status on TG in elderly in-patients. After 6-month follow-up, major bleeding/thromboembolic event/death rates were 6.7%/1.0%/17.3% in rivaroxaban and 5.4%/3.6%/18.9% in apixaban patients, respectively.

CONCLUSION

 Our study provides original data in very elderly patients receiving DOAC in a real-life setting, showing great inter-individual variability in plasma concentrations and TG parameters. Further research is needed to understand the potential clinical impact of these findings.

Are Viscoelastometric Assays of Old Generation Ready for Disposal? Comment on Volod et al. Viscoelastic Hemostatic Assays: A Primer on Legacy and New Generation Devices. J. Clin. Med. 2022, 11, 860

With the advent of new viscoelastometric hemostatic assay (VHA) devices, with ready-to-use cartridge reagents allowing for their use by people without special laboratory skills, the appreciation of the actual clinical value of VHAs in settings such as severe trauma, post-partum hemorrhage, cardiac surgery and liver transplantation still needs to be fully validated. While two of the newest versions remain based on a 'cup and pin' system (ROTEM^® sigma, ClotPro^®), two other new devices (TEG^® 6s, Quantra^®) rely on very different technologies: clotting blood is no longer in contact with the probe and challenged by oscillation of one of the components but explored with ultrasound exposure. A systematic literature search (including Sonoclot^®) retrieved 20 observational studies (19 prospective). Most studies pointed to imperfect agreements, highlighting the non-interchangeability of devices. Only a few studies, often with a limited number of patients enrolled, used a clinical outcome. No study compared VHA results with conventional laboratory assays obtained through a rapid tests panel. Clinical evidence of the utility of the new VHAs largely remains to be proven through randomized clinical trials, with clinically relevant outcomes, and compared to rapid panel hemostasis testing. The availability of new, improved VHA devices provides an impetus and an opportunity to do so.

Laboratory evaluation of a new integrative assay to phenotype plasma fibrinolytic system

BACKGROUND

There is currently no universal and standardized test available to phenotype plasma fibrinolytic system.

AIMS

Our main aims were to evaluate the performances of the 'global fibrinolysis capacity' assay (GFC) performed with the Lysis Timer® instrument, and to study the influence of some preanalytical conditions.

METHOD

Euglobulin clot lysis time (ECLT) and GFC were performed under several preanalytical conditions.

RESULTS

GFC showed satisfactory intra- and inter-run precision. Frozen controls and reagents showed stability over the studied period. There was no statistically significant difference between GFC assessed in plasma samples processed at 4 °C or at 20 °C. GFC assessed with frozen-thawed plasma samples was prolonged when compared to fresh samples (p = 0.014). The centrifugation scheme had no influence on PAI-1 activity levels, GFC and ECLT. Reference interval for GFC ranges from 29.3 (C I90% = 26.9-31.9) to 49.5 (90% CI = 45.9-52.2) minutes. In addition, a preliminary study in 40 healthy volunteers and 43 adult patients referred for investigation of a bleeding disorder was conducted to compare GFC and ECLT assays in their ability to classify samples with shortened or prolonged clot lysis times. Disagreements between ECLT and GFC were observed for 23 samples (out of 83), most of them minor.

CONCLUSION

GFC is suitable and convenient for a broad clinical use and can be performed with frozen-thawed plasma samples. Unlike ECLT, GFC is designed to take into account the balance between inhibitors and activators of the fibrinolytic system and could detect both hypo- and hyperfibrinolytic states. Whether it is as suitable as or even better than ECLT to detect a bleeding tendency due to a hyperactive fibrinolytic system deserves to be properly investigated.

External validation of the MidiCAT variant of thrombography: Comparison with calibrated automated thrombography and study of the centrifugation scheme

Introduction

To perform Calibrated Automated Thrombography (CAT), the use of reduced plasma volumes (referred to as “MidiCAT”) makes it possible to more efficiently use limited volumes of valuable biobanked plasma samples and decreases expenses for reagents. It is, however, unclear whether the MidiCAT procedure is suitable when thrombin generation (TG) is studied in the presence of added thrombomodulin (TG-TM). Moreover, a simplified centrifugation scheme would facilitate biobanking, if appropriate, for more sensitive coagulation studies. We aimed to compare the results of “MidiCAT” (halved plasma and reagent volumes) with those from regular CAT, in the absence or presence of TM, as well as to study the impact of a single-centrifugation scheme for plasma preparation before freezing.

Materials and methods

Plasma samples were prepared from the citrated blood from 20 Geneva hospital diverse patients without gross coagulation abnormalities with a single- or double-centrifugation scheme. Samples were kept frozen at −80°C and thawed just before the TG assay in duplicate under two conditions: 1 pM tissue factor (TF) or 5 pM TF + TM.

Results and discussion

(1) We externally validated “MidiCAT” and also extended the validation to TG-TM. Whatever the method (CAT or MidiCAT), intra-assay (assessed with duplicates) CV was below 6% (1 pM TF) or below 10% (5 pM TF + TM) for ETP. Agreement between the MidiCAT and CAT results was satisfactory; the p coefficients were above 0.95 for ETP and above 0.90 for most other parameters; biases for ETP were +10.0% (1 pM FT) and +13.5% (5 pM + TM). (2) The centrifugation scheme markedly affected the results obtained in the presence of TM, whereas the bias and limit of agreement (difference plots) were low for the no TM condition. The bias in the presence of TM was obvious, more marked with plasma samples sensitive to TM when double centrifuged: the lower the ETP-TM, the greater the relative difference between the ETP-TM of plasma samples prepared with just single centrifugation and the reference plasma samples. Thus, a single-centrifugation procedure, as is often used for plasma biobanking, is suitable for TG study only if it is not performed in the presence of TM.

Differential impact of tamoxifen and aromatase inhibitors on thrombin generation: the prospective HEMOBREAST cohort

Tamoxifen and aromatase inhibitors (AIs) are potent antitumoral agents against breast cancer. Tamoxifen increases the risk of venous thromboembolism (VTE), but the influence of AIs on the risk of VTE remains unclear. To inform clinical decisions, we evaluated associations of tamoxifen or AIs with changes of surrogate hemostatic biomarkers. This prospective cohort included 107 women with localized breast cancer starting tamoxifen (n = 42) or an AI (n = 65). Thrombin generation (CAT) its sensitivity to thrombomodulin (TM) or activated protein C (APC), and specific coagulation parameters, were measured before and 10-16 weeks after initiation of treatmen Compared with baseline, endogenous thrombin potential and thrombin peak increased in tamoxifen users (+86 nM × min; 95% confidence interval [CI], 30-142; and +33 nM; 95% CI, 21-45) but not in AI users (n = 65; +44 nM × min; 95% CI, -4 to 93; and +7 nM; 95% CI, -3 to 17). Normalized TM sensitivity ratios increased with tamoxifen (+0.26; 95% CI, 0.19-0.33y) but not with AI (+0.02; 95% CI, -0.03 to 0.07). Plasma levels of fibrinogen, antithrombin, protein C, and Tissue Factor Pathway Inhibitor decreased, and free protein S increased with tamoxifen but not with AIs. The observed shift toward increased coagulability associated with tamoxifen is in line with its known increased risk of VTE. In contrast, AIs do not appear to impact hemostasis, suggesting a lack of associated VTE risk. The trial was registered at www.clinicaltrials.gov as #NCT03381963.

Alpha-2-macroglobulin in hemostasis and thrombosis: An underestimated old double-edged sword

Antiproteinases such as alpha-2-macroglobulin (A2M) play a role in hemostasis. A2M is highly conserved throughout evolution and is a high molecular weight homo-tetrameric glycoprotein. A2M proteinase inhibitor activity is possible via a unique cage structure leading to proteinase entrapment without direct enzymatic activity inhibition. Following this entrapment, proteinase clearance is possible through A2M binding to the low-density lipoprotein receptor-related protein 1. A2M synthesis is regulated by pro-inflammatory cytokines and increases during several chronic or acute inflammatory diseases and varies with age. For instance, A2M plasma levels are known to be increased in patients with diabetes mellitus, nephrotic syndrome, or sepsis. Concerning hemostasis, A2M can trap many proteinases involved in coagulation and fibrinolysis. Because of its pleiotropic effects A2M can be seen as both anti- and pro-hemostatic. A2M can inhibit thrombin, factor Xa, activated protein C, plasmin, tissue-plasminogen activator, and urokinase. Through its many different functions A2M is generally put apart in the balanced regulation of hemostasis. In addition, the fact that A2M plasma levels are differently regulated during inflammatory-related diseases and that A2M can neutralize cytokines that also modify hemostasis could explain why it is difficult to link common proteins and parameters of hemostasis with the mechanisms of thrombosis in such diseases. Thus, we propose in the present review to summarize known functions of A2M, give a brief overview about diseases, and then to focus on the roles of this antiproteinase in hemostasis and thrombosis.

Impact of fibrinogen infusion on thrombin generation and fibrin clot structure in patients with inherited afibrinogenemia

INTRODUCTION

Inherited afibrinogenemia is a very rare disease characterized by complete absence of fibrinogen in the circulation and an increased risk in both thrombosis and bleeding. Infusion of fibrinogen concentrate (FC) is the main approach for prevention and management of bleeding; however, it has been reported to carry a thrombotic risk.

METHODS

We investigated the impact of a standard dose (40-100 mg/kg) of FC infusion on the thrombin generation (TG) parameters and the fibrin clot structure formed in plasma samples of patients with afibrinogenemia. Blood samples were collected from 20 patients before (T0) and 1 hour after infusion of FC (T1). TG was studied with Calibrated Automated Thrombography. Fibrin clot structure was assessed with turbidimetry and scanning electron microscopy (SEM).

RESULTS

FC infusions (mean Clauss fibrinogen plasma level 1.21 g/L at T1) led to a statistically significant increase in endogenous thrombin potentials (ETP) (p<0.0001) and thrombin peaks (p=0.02). Nevertheless, when compared to healthy controls, patients' T1 lag times were longer (p=0.002), ETP values were lower (p=0.0003), and thrombin peaks were lower (p<00001). All fibrin polymerization parameters (turbidimetry) obtained at T1 were comparable to those of patients with inherited hypofibrinogenemia matched for fibrinogen plasma levels.

CONCLUSIONS

In summary, fibrinogen infusion with a standard dose of FC increased but did not correct TG and led to formation of fibrin clots similar to those of patients with hypofibrinogenemia. All in all, our results do not support to biological evidence of hypercoagulability induced by FC in patients with afibrinogenemia.

GFHT Proposals On The Practical Use Of Argatroban - With Specifics Regarding Vaccine-Induced Immune Thrombotic Thrombocytopaenia (VITT)

Argatroban is a direct anti-IIa (thrombin) anticoagulant, administered as a continuous intravenous infusion; it has been approved in many countries for the anticoagulant management of heparin-induced thrombocytopaenia (HIT). Argatroban was recently proposed as the non-heparin anticoagulant of choice for the management of patients diagnosed with Vaccine-induced Immune Thrombotic Thrombocytopaenia (VITT). Immunoglobulins are also promptly intravenously administered in order to rapidly improve platelet count; concomitant therapy with steroids is also often considered. An ad hoc committee of the French Working Group on Haemostasis and Thrombosis members has worked on updated and detailed proposals regarding the management of anticoagulation with argatroban, based on previously released guidance for HIT, and adapted for VITT. In case of VITT, the initial dose to be preferred is 1.0 µg x kg^-1 x min^-1, with further dose-adjustments based on iterative and frequent clinical and laboratory assessments. It is strongly advised to involve a health practitioner experienced in the management of difficult cases in haemostasis. The first laboratory assessment should be performed 4 hours after the initiation of argatroban infusion, with further controls at 2-4-hour intervals until steady state, and at least once daily thereafter. Importantly, full anticoagulation should be rapidly achieved in case of widespread thrombosis. Cerebral vein thrombosis (which is typical of VITT) should not call for an overly cautious anticoagulation scheme. Argatroban administration requires baseline laboratory assessment and should rely on an anti-IIa assay to derive argatroban plasma levels using a dedicated calibration, with a target range between 0.5 and 1.5 µg/mL. Target argatroban plasma levels can be refined based on meticulous appraisal of risk factors for bleeding and thrombosis, on frequent reassessments of clinical status with appropriate vascular imaging, and on the changes in daily platelet counts. Regarding the use of aPTT, baseline value and possible causes for alterations of the clotting time must be taken into account. Specifically, in case of VITT, an aPTT ratio (patient's / mean normal clotting time) between 1.5 and 2.5 is suggested, to be refined according to the sensitivity of the reagent to the effect of a direct thrombin inhibitor. The sole use of aPTT is discouraged: one has to resort to a periodical check with an anti-IIa assay at least, with the help of a specialised laboratory if necessary. Dose modifications should proceed in a stepwise manner with 0.1 to 0.2 µg x kg^-1 x min^-1 up- or downward changes, taking into account the initial dose, laboratory results, and the whole individual setting. Nomograms are available to adjust the infusion rate. Haemoglobin level, platelet count, fibrinogen plasma level and liver tests should be periodically checked, depending on the clinical status, the more so when unstable.

Study of in vitro thrombin generation after neutralization of heparin

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.

NETosis and the Immune System in COVID-19: Mechanisms and Potential Treatments

NETosis is a form of neutrophil death leading to the release of extracellular chromatin and the assembling of proteins, including antiviral proteins, primed by an initial pathogenic stimulus. Under certain specific conditions, neutrophils can exhibit a double-edged activity. This event has been implicated in COVID-19 among other conditions. Neutrophil extracellular traps (NETs) are involved in the pathogenesis of COVID-19 by promoting a pro-inflammatory and a procoagulant state leading to multiorgan failure. This particular form of host defense promoted by neutrophils is closely related to the well-known cytokine storm observed in severe COVID-19 patients. These two elements therefore represent possible targets for treatment of severe SARS-CoV-2 infections.

Heparin-induced thrombocytopenia: Construction of a pretest diagnostic score derived from the analysis of a prospective multinational database, with internal validation

BACKGROUND

Diagnosis of heparin-induced thrombocytopenia (HIT) requires pretest probability assessment and dedicated laboratory assays.

OBJECTIVE

To develop a pretest score for HIT.

DESIGN

Observational; analysis of prospectively collected data of hospitalized patients suspected with HIT (ClinicalTrials.gov NCT00748839).

SETTING

Thirty-one tertiary hospitals in France, Switzerland, and Belgium.

PATIENTS

Patients tested for HIT antibodies (2280 evaluable), randomly allocated to derivation and validation cohorts.

MEASUREMENTS

Independent adjudicators diagnosed HIT based on the prospectively collected data and serotonin release assay results.

RESULTS

Heparin-induced thrombocytopenia was diagnosed in 234 (14.7%) and 99 (14.5%) patients in the two cohorts. Eight features were associated with HIT (in brackets, points assigned for score calculation of the score): unfractionated heparin (1); therapeutic-dose heparin (1); cardiopulmonary bypass (cardiac surgery) (2); major trauma (3); 5- to 21-day interval from anticoagulation initiation to suspicion of HIT (4); ≥40% decrease in platelet count over ≤6 days (3); thrombotic event, arterial (3) or venous (3). The C-statistic was 0.79 (95% CI, 0.76-0.82). In the validation cohort, the area under the receiver operating characteristic curve was 0.77 (95% CI, 0.74-0.80). Three groups of scores were defined; HIT prevalence reached almost 30% in the high-probability group.

LIMITATION

The performance of the score may depend on settings and practices.

CONCLUSION

The objective, easy-to-collect, clinical features of HIT we evidenced were incorporated into a pretest score, which may guide clinical decisions regarding diagnostic testing and anticoagulation.

Hypotheses behind the very rare cases of thrombosis with thrombocytopenia syndrome after SARS-CoV-2 vaccination

As of 4 April 2021, a total of 169 cases of cerebral venous sinus thrombosis (CVST) and 53 cases of splanchnic vein thrombosis were reported to EudraVigilance among around 34 million people vaccinated in the European Economic Area and United Kingdom with COVID-19 Vaccine AstraZeneca, a chimpanzee adenoviral vector (ChAdOx1) encoding the spike protein antigen of the SARS-CoV-2 virus. The first report of the European Medicines Agency gathering data on 20 million people vaccinated with Vaxzevria® in the UK and the EEA concluded that the number of post-vaccination cases with thromboembolic events as a whole reported to EudraVigilance in relation to the number of people vaccinated was lower than the estimated rate of such events in the general population. However, the EMA's Pharmacovigilance Risk Assessment Committee concluded that unusual thromboses with low blood platelets should be listed as very rare side effects of Vaxzevria®, pointing to a possible link. The same issue was identified with the COVID-19 Vaccine Janssen (Ad26.COV2.S). Currently, there is still a sharp contrast between the clinical or experimental data reported in the literature on COVID-19 and the scarcity of data on the unusual thrombotic events observed after the vaccination with these vaccines. Different hypotheses might support these observations and should trigger further in vitro and ex vivo investigations. Specialized studies were needed to fully understand the potential relationship between vaccination and possible risk factors in order to implement risk minimization strategies.

Viscoelastometric Testing to Assess Hemostasis of COVID-19: A Systematic Review

Infection by SARS-CoV-2 is associated with a high risk of thrombosis. The laboratory documentation of hypercoagulability and impaired fibrinolysis remains a challenge. Our aim was to assess the potential usefulness of viscoelastometric testing (VET) to predict thrombotic events in COVID-19 patients according to the literature. We also (i) analyzed the impact of anticoagulation and the methods used to neutralize heparin, (ii) analyzed whether maximal clot mechanical strength brings more information than Clauss fibrinogen, and (iii) critically scrutinized the diagnosis of hypofibrinolysis. We performed a systematic search in PubMed and Scopus databases until 31st December 2020. VET methods and parameters, and patients' features and outcomes were extracted. VET was performed for 1063 patients (893 intensive care unit (ICU) and 170 non-ICU, 44 studies). There was extensive heterogeneity concerning study design, VET device used (ROTEM, TEG, Quantra and ClotPro) and reagents (with non-systematic use of heparin neutralization), timing of assay, and definition of hypercoagulable state. Notably, only 4 out of 25 studies using ROTEM reported data with heparinase (HEPTEM). The common findings were increased clot mechanical strength mainly due to excessive fibrinogen component and impaired to absent fibrinolysis, more conspicuous in the presence of an added plasminogen activator. Only 4 studies out of the 16 that addressed the point found an association of VETs with thrombotic events. So-called functional fibrinogen assessed by VETs showed a variable correlation with Clauss fibrinogen. Abnormal VET pattern, often evidenced despite standard prophylactic anticoagulation, tended to normalize after increased dosing. VET studies reported heterogeneity, and small sample sizes do not support an association between the poorly defined prothrombotic phenotype of COVID-19 and thrombotic events.

Functional Flow Cytometric Assay for Reliable and Convenient Heparin-Induced Thrombocytopenia Diagnosis in Daily Practice

Reliable laboratory diagnosis of heparin-induced thrombocytopenia (HIT) remains a major clinical concern. Immunoassays are highly sensitive, while confirmatory functional tests (based on heparin-dependent platelet activation) lack standardization. We evaluated the diagnostic performance of a functional flow cytometric assay (FCA) based on the detection of heparin-dependent platelet activation with an anti-p-selectin. A total of 288 patients were included (131 HIT-positive and 157 HIT-negative) with a HIT diagnosis established by expert opinion adjudication (EOA) considering clinical data and local laboratory results. The FCA was centrally performed in a single laboratory on platelet-rich plasma, using a very simple four-color fluorometer. The results were standardized according to the Heparin Platelet Activation (HEPLA) index. The serotonin release assay (SRA) was performed in the four French reference laboratories. Based on the final HIT diagnosis established by EOA, the sensitivity and specificity of the FCA were 88 and 95%, respectively, values very similar to those of the SRA (88 and 97%, respectively). This study showed that the FCA, based on easily implementable technology, may be routinely used as a reliable confirmatory test for HIT diagnosis.

Study of thrombin generation with St Genesia to evaluate xaban pharmacodynamics: Analytical performances over 18 months

INTRODUCTION

ST Genesia is a new automated system enabling quantitative standardized evaluation of thrombin generation (TG), for example, in patients receiving anti-Xa direct inhibitors (xabans). Data on its analytical performances are scarce.

METHODS

Over an 18-month period, repeatability, reproducibility, and accuracy were assessed using STG-ThromboScreen (without or with thrombomodulin) or STG-DrugScreen reagents (corresponding to intermediate/high tissue-factor concentration, respectively), and controls. Furthermore, reproducibility was assessed using commercialized lyophilized and frozen normal pooled plasmas. Rivaroxaban and apixaban impacts on TG parameters were assessed using spiking experiments. Finally, a comparison with the Calibrated Automated Thrombogram method (CAT) (PPP reagent) was performed using plasma from healthy volunteers enrolled in the DRIVING-studyNCT01627665) before and after rivaroxaban intake.

RESULTS

For all dedicated quality control (QC) levels, inter-series coefficients of variations (CV) were <7% for temporal TG parameters, peak height (PH), and endogenous thrombin potential (ETP), whether results were normalized with a dedicated reference plasma STG-RefPlasma or not. Noteworthy, STG-RefPlasma used for normalization displayed substantially high PH and ETP. Mean biases between the observed and manufacturer's assigned QC values were mostly <7%. Both rivaroxaban/apixaban plasma concentrations were significantly associated with TG parameters. Finally, Bland-Altman plots showed a good agreement between ST Genesia-STG-ThromboScreen and CAT method within the explored range of values, although biases could be observed (PH: 16.4 ± 13.2%, ETP: 17.8 ± 11.9%).

CONCLUSION

ST Genesia^® enables the reliable measurement of TG parameters in both in vitro and ex vivo xaban plasma samples using either STG-ThromboScreen or STG-DrugScreen according to xaban concentrations. The use of reference plasma, despite not completely reflecting a normal pooled plasma behavior, likely improves standardization and inter-laboratory comparisons.

Prothrombotic hemostasis disturbances in patients with severe COVID-19: Individual daily data

This data article accompanies the manuscript entitled: “Prothrombotic Disturbances of hemostasis of Patients with Severe COVID-19: a Prospective Longitudinal Observational Cohort Study” submitted to Thrombosis Research by the same authors. We report temporal changes of plasma levels of an extended set of laboratory parameters during the ICU stay of the 21 COVID-19 patients included in the monocentre cohort: CRP, platelet count, prothrombin time; Clauss fibrinogen and clotting factors II, V and VIII levels, D-dimers, antithrombin activity, protein C, free protein S, total and free tissue factor pathway inhibitor, PAI-1 levels, von Willebrand factor antigen and activity, ADAMTS-13 (plasma levels); and of two integrative tests of coagulation (thrombin generation with ST Genesia) and fibrinolysis (global fibrinolytic capacity - GFC). Regarding hemostasis, we used double-centrifuged frozen citrated plasma prospectively collected after daily performance of usual coagulation tests. Demographic and clinical characteristics of patients and thrombotic and hemorrhagic complications were also collected from patient's electronic medical reports.

Assessment of Shear-Dependent Kinetics of Primary Haemostasis With a Microfluidic Acoustic Biosensor

Primary haemostasis is a complex dynamic process, which involves in-flow interactions between platelets and sub-endothelial matrix at the area of the damaged vessel wall. It results in a first haemostatic plug, which stops bleeding, before coagulation ensues and consolidates it. The diagnosis of primary haemostasis defect would benefit from evaluation of the whole sequence of mechanisms involved in platelet plug formation in flow. This work proposes a new approach that is based on characterization of the shear-dependent kinetics that enables the evaluation of the early stages of primary haemostasis. We used a label-free method with a quartz crystal microbalance (QCM) biosensor to measure the platelet deposits over time onto covalently immobilized type I fibrillar collagen. We defined three metrics: total frequency shift, lag time, and growth rate. The measurement was completed at four predefined shear rates prevailing in small vessels (500, 770, 1000 and 1500 s^-1) during five minutes of perfusion with anticoagulated normal whole blood. The rate of the frequency shift over the first five minutes was strongly influenced by shear rate conditions, presenting a maximum around 770 s^-1, and varying by a factor larger than three in the studied shear rate range. To validate the biosensor signal, the total frequency shift was compared to results obtained by atomic force microscopy (AFM) on final platelet deposits. The results show that shear-dependent kinetic assays are promising as an advanced method for screening of primary haemostasis.

Management of the thrombotic risk associated with COVID-19: guidance for the hemostasis laboratory

Coronavirus disease 2019 (COVID-19) is associated with extreme inflammatory response, disordered hemostasis and high thrombotic risk. A high incidence of thromboembolic events has been reported despite thromboprophylaxis, raising the question of a more effective anticoagulation. First-line hemostasis tests such as activated partial thromboplastin time, prothrombin time, fibrinogen and D-dimers are proposed for assessing thrombotic risk and monitoring hemostasis, but are vulnerable to many drawbacks affecting their reliability and clinical relevance. Specialized hemostasis-related tests (soluble fibrin complexes, tests assessing fibrinolytic capacity, viscoelastic tests, thrombin generation) may have an interest to assess the thrombotic risk associated with COVID-19. Another challenge for the hemostasis laboratory is the monitoring of heparin treatment, especially unfractionated heparin in the setting of an extreme inflammatory response. This review aimed at evaluating the role of hemostasis tests in the management of COVID-19 and discussing their main limitations.

Hypercoagulability (thrombin generation) in patients with cirrhosis is detected with ST-Genesia

BACKGROUND

Thrombin generation assays (TGAs) performed with calibrated automated thrombography (CAT) in the presence of thrombomodulin (TM) indicate plasma hypercoagulability in cirrhosis.

OBJECTIVE

To evaluate, in the presence of TM, the new ST-Genesia automated device developed for improving TGA vs the previously used CAT method, with plasma samples of patients with cirrhosis.

PATIENTS/METHODS

Platelet-poor plasma samples were prepared from citrated blood samples of 52 healthy controls and 85 patients with cirrhosis (severity evaluated using the Child-Pugh score [CP]). TGAs were performed using CAT with PPP-Reagent and ST-Genesia with the STG-ThromboScreen reagent, in the presence of TM. Endogenous thrombin potential (ETP) was chosen as the main parameter.

RESULTS

Whatever the method, ETP values were higher in patients than in healthy controls. All patients identified as hypercoagulable with ST-Genesia and STG-ThromboScreen were found hypercoagulable with CAT and PPP-Reagent. Conversely, eight and ten patients in the CP-A and CP-B classes respectively were identified as hypercoagulable only with CAT. The use of ST-Genesia with the STG-ThromboScreen reagent with TM led to a bias, with higher ETP values for healthy controls and lower for patients compared with CAT. Crossover analysis (CAT with the STG-ThromboScreen reagent) evidenced a substantial effect of the STG-ThromboScreen reagent; the analyzer (including calibration and data analysis) plays a lesser role.

CONCLUSION

ST-Genesia evidences hypercoagulability in patients with cirrhosis when TG is studied in the presence of TM, but the results are not interchangeable with those obtained with CAT.

Thrombin Generation and Cirrhosis: State of the Art and Perspectives

Epidemiological and laboratory studies performed in the last decades have changed our understanding of coagulopathy in cirrhosis, from a condition at increased risk of hemorrhagic events to one at higher thrombotic risk. However, it is not clear whether the decrease in factors that promote (except factor [F] VIII) versus inhibit coagulation in patients with cirrhosis results in a rebalanced state or in a hypercoagulable phenotype. This issue can be partially addressed using thrombin generation assays (TGA), which unlike routine clotting tests (prothrombin time or activated partial thromboplastin time) are sensitive to both procoagulant factors and coagulation inhibitors. However, many preanalytical issues and variable analytical methodologies used in TGAs complicate data analysis and interlaboratory comparisons. The introduction of TGAs in which activators of the protein C pathway (particularly soluble forms of thrombomodulin [TM]) are added has allowed detection of a reduced anticoagulant effect of TM or even a hypercoagulable phenotype as judged by endogenous thrombin potential. However, inter- and intra-assay variability may be greater with this TGA variant compared with "standard" TGAs. TGAs also allowed identifying main determinants of the hypercoagulability phenotype in the presence of TM: acquired antithrombin and protein C deficiencies, and elevated FVIII levels. The aim of this narrative review is to summarize the preanalytical and methodological variables of TGAs and also the findings of the main studies that have evaluated TGAs in patients with cirrhosis. The review also provides some propositions for future studies and outlines some perspectives on the potential implementation of this promising tool in clinical practice for the study of coagulation in patients with cirrhosis.

Anti–Domain I β2-Glycoprotein I Antibodies and Activated Protein C Resistance Predict Thrombosis in Antiphospholipid Syndrome: TAC(I)T Study

Background

Antibodies binding to domain I of β2-glycoprotein I (aDI) and activated protein C (APC) resistance are associated with an increased risk of thrombosis in cross-sectional studies. The objective of this study was to assess their predictive value for future thromboembolic events in patients with antiphospholipid antibodies (aPL) or antiphospholipid syndrome.

Methods

This prospective multicenter cohort study included consecutive patients with aPL or systemic lupus erythematosus. We followed 137 patients (43.5 ± 15.4 year old; 107 women) for a mean duration of 43.1 ± 20.7 months.

Results

We detected aDI IgG antibodies by ELISA in 21 patients. An APC sensitivity ratio (APCsr) was determined using a thrombin generation–based test. The APCsr was higher in patients with anti–domain I antibodies demonstrating APC resistance (0.75 ± 0.13 vs 0.48 ± 0.20, P &lt; 0.0001). In univariate analysis, the hazard ratio (HR) for thrombosis over time was higher in patients with aDI IgG (3.31 [95% CI, 1.15–9.52]; P = 0.03) and patients with higher APC resistance (APCsr &gt;95th percentile; HR, 6.07 [95% CI, 1.69–21.87]; P = 0.006). A sensitivity analysis showed an increased risk of higher aDI IgG levels up to HR 5.61 (95% CI, 1.93–16.31; P = 0.01). In multivariate analysis, aDI IgG (HR, 3.90 [95% CI, 1.33–11.46]; P = 0.01) and APC resistance (HR, 4.98 [95% CI, 1.36–18.28]; P = 0.02) remained significant predictors of thrombosis over time.

Conclusions

Our study shows that novel tests for antibodies recognizing domain I of β2-glycoprotein I and functional tests identifying APC resistance are significant predictors of thrombosis over time and may be useful for risk stratification.

Detection of Platelet-Activating Antibodies Associated with Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic immune drug reaction caused by platelet-activating antibodies that in most instances recognize platelet factor 4 (PF4)/polyanion complexes. Platelet activation assays (i.e., functional assays) are more specific than immunoassays, since they are able to discern clinically relevant heparin-induced antibodies. All functional assays used for HIT diagnosis share the same principle, as they assess the ability of serum/plasma from suspected HIT patients to activate fresh platelets from healthy donors in the presence of several concentrations of heparin. Depending on the assay, donors’ platelets are stimulated either in whole blood (WB), platelet-rich plasma (PRP), or in a buffer medium (washed platelets, WP). In addition, the activation endpoint studied varies from one assay to another: platelet aggregation, membrane expression of markers of platelet activation, release of platelet granules. Tests with WP are more sensitive and serotonin release assay (SRA) is considered to be the current gold standard, but functional assays suffer from certain limitations regarding their sensitivity, specificity, complexity, and/or accessibility. However, the strict adherence to adequate preanalytical conditions, the use of selected platelet donors and the inclusion of positive and negative controls in each run are key points that ensure their performances.

Recommendations on the use of anticoagulants for the treatment of patients with heparin-induced thrombocytopenia in Switzerland

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse drug effect that occurs in 0.1&ndash;5% of heparin treated patients. Management of acute HIT currently involves (1) cessation of heparin exposure, and (2) inhibition of coagulation with an anticoagulant other than heparin. Several anticoagulants can be considered for the treatment of HIT. Anticoagulant monitoring, management of drug-induced adverse events including bleeding, and therapeutic dosing schedules in selected clinical settings represent challenges to the clinician treating HIT patients. Moreover, the fact that not all registered anticoagulants are approved for HIT in Switzerland further complicates the management of HIT. The present recommendations on the anticoagulant treatment of HIT in Switzerland have been elaborated by a panel of Swiss experts belonging to the Working Party Hemostasis (WPH) of the Swiss Society of Hematology (SGH-SSH). They are intended to support clinicians in their decision making when treating HIT patients.