Mepacrine flow cytometry assay for the diagnosis of platelet δ-granule defects : literature review on methods - towards a shared detailed protocol.

Accurate assessment of platelet secretion is essential for the diagnosis of inherited or acquired platelet function disorders (PFDs) and more specifically in identifying δ-storage pool disease. Mepacrine, a fluorescent dye, specifically accumulates in platelet δ-granules. The mepacrine flow cytometry (FCM) assay has been used for more than half a century in the clinical laboratory as a diagnostic tool for platelet δ-granule disorders. The assay requires a small volume of blood, can be performed in thrombocytopenic patients, provides rapid assessment of δ-granule content and secretion and, thus, enables differentiation between storage and release defects. FCM has been shown to have added value compared to light transmission aggregometry. There is however a broad heterogeneity in methods, reagents, and equipment used. Lack of standardization and limited data on analytical and clinical performances have led the 2022 ISTH SSC Subcommittee on Platelet Physiology expert consensus to rate this assay as simple but of uncertain value. Yet, the data used by experts to formulate the recommendations were not discussed and even not mentioned. Guidance for laboratory studies of platelet secretion assay would be very helpful for clinical laboratories and health authorities especially considering the implications of the new In Vitro Diagnostic Regulation (IVDR) in Europe. The purpose of the present work was to systematically review the reported methodologies for the mepacrine FCM assay and to offer an example of detailed protocol. This would help standardization and pave the way for more rigorous comparative studies.

Direct oral anticoagulants in cirrhosis: Rationale and current evidence.

Cirrhosis is a major health concern worldwide with a complex pathophysiology affecting various biological systems, including all aspects of haemostasis. Bleeding risk is mainly driven by portal hypertension, but in end-stage liver disease it is further increased by alterations in haemostatic components, including platelet function, coagulation, and fibrinolysis. Concurrently, patients with cirrhosis are prone to venous thromboembolic events (VTE) because of the altered haemostatic balance, in particular an increase in thrombin generation. In patients with cirrhosis, vitamin K antagonists (VKA) and low molecular weight heparins (LMWH) are currently the standard of care for VTE prevention, with VKA also being standard of care for stroke prevention in those with atrial fibrillation. However, direct oral anticoagulants (DOAC) could have specific advantages in this patient population. Clinical experience suggests that DOAC are a safe and possibly more effective alternative to traditional anticoagulants for the treatment of VTE in patients with compensated cirrhosis. In addition, emerging data suggest that primary prophylactic treatment with anticoagulants may improve clinical outcomes in patients with cirrhosis by reducing the risk of hepatic decompensation. The selection of the most appropriate DOAC remains to be clarified. This review focuses on the rationale for the use of DOAC in patients with cirrhosis, the specific effects of the different DOAC (as assessed by in vitro and in vivo pharmacokinetic and pharmacodynamic studies), as well as clinical outcomes in patients with cirrhosis on DOAC.

Dabigatran accumulation in acute kidney injury: is more better than less to prevent bleeding? A case report.

Dabigatran is an oral anticoagulant that is mainly renally excreted. Despite its efficacy in preventing thromboembolic events, concerns arise regarding bleeding complications in patients with acute kidney injury. Idarucizumab is its specific antidote and reverses quickly and effectively dabigatran anticoagulation effects in situations of severe bleeding or pending surgical procedures, but its benefit beyond these two indications remains uncertain. We present a case of a woman with atrial fibrillation anticoagulated by dabigatran and admitted with Streptococcus agalactiae meningitis, acute kidney injury and dabigatran accumulation. Idarucizumab was not administered initially as she did not meet its current strict indications. However, subsequently, significant bleeding necessitated its use. A rebound increase in dabigatran concentration was associated with an intracranial hemorrhage, but the combination of additional doses of idarucizumab with hemodialysis lowered the dabigatran concentration and prevented significant rebound increases. Further investigation into the optimal management of dabigatran accumulation and acute kidney injury-associated bleeding is needed to enhance patient outcomes and safety. Early initiation of hemodialysis together with idarucizumab administration may be crucial in preventing life-threatening bleeding events in these patients.

High prevalence of short telomeres in idiopathic porto-sinusoidal vascular disorder.

BACKGROUND: Telomeres prevent damage to coding DNA as end-nucleotides are lost during mitosis. Mutations in telomere maintenance genes cause excessive telomere shortening, a condition known as short telomere syndrome (STS). One hepatic manifestation documented in STS is porto-sinusoidal vascular disorder (PSVD). METHODS: As the etiology of many cases of PSVD remains unknown, this study explored the extent to which short telomeres are present in patients with idiopathic PSVD. RESULTS: This monocentric cross-sectional study included patients with histologically defined idiopathic PSVD. Telomere length in 6 peripheral blood leukocyte subpopulations was assessed using fluorescent in situ hybridization and flow cytometry. Variants of telomere-related genes were identified using high-throughput exome sequencing. In total, 22 patients were included, of whom 16 (73%) had short (9/22) or very short (7/22) telomeres according to age-adjusted reference ranges. Fourteen patients (64%) had clinically significant portal hypertension. Shorter telomeres were more frequent in males (p = 0.005) and patients with concomitant interstitial lung disease (p < 0.001), chronic kidney disease (p < 0.001), and erythrocyte macrocytosis (p = 0.007). Portal hypertension (p = 0.021), low serum albumin level (p < 0.001), low platelet count (p = 0.007), and hyperbilirubinemia (p = 0.053) were also associated with shorter telomeres. Variants in known STS-related genes were identified in 4 patients with VSTel and 1 with STel. CONCLUSIONS: Short and very short telomeres were highly prevalent in patients with idiopathic PSVD, with 31% presenting with variants in telomere-related genes. Telomere biology may play an important role in vascular liver disease development. Clinicians should consider measuring telomeres in any patient presenting with PSVD.

Global coagulation assays detect an early prothrombotic state in children with acute lymphoblastic leukemia.

BACKGROUND: Pediatric patients with acute lymphoblastic leukemia (ALL) are at highest risk of venous thromboembolism during the induction therapy (IT). These events are not predictable by conventional coagulation assays. OBJECTIVES: To investigate the utility of global coagulation assays (GCAs) for assessing the hemostatic state in children with ALL during IT. METHODS: We included children with ALL (n = 15) and healthy controls (n = 15). Analyses were performed at different time points during IT of the AIEOP-BFM protocols. In addition to prothrombotic biomarkers, natural anticoagulant proteins, and in vivo thrombin generation (TG) markers, ex vivo TG was measured using the gold standard calibrated automated thrombogram method, automated ST Genesia, and thrombodynamics analyzer (TD). The latter also provided measurement of fibrin clot formation. RESULTS: Different from conventional coagulation assays and in vivo TG markers, ex vivo GCAs detected increasing prothrombotic changes during IT. Particularly, TG measured with TD as expressed by endogenous thrombin potential was already significantly elevated at days 8 to 12 (P < .01) and continued to increase during IT compared with prior to beginning treatment, indicating a very early shift toward a procoagulant state. A similar pattern was observed for the rate of fibrin clot formation (stationary rate of clot growth: P < .01 at days 8-12). Remarkably, in patients developing thrombotic complications (n = 5), both GCAs, ST Genesia and TD, showed a significantly higher endogenous thrombin potential very early (already at days 8-12, P < .05), well before clinical manifestation. CONCLUSION: GCAs capture prothrombotic changes early during IT in ALL pediatric patients. If confirmed, this approach will allow tailoring thromboprophylaxis in children with ALL at highest risk for venous thromboembolism.

Increase of Phosphoprotein Expressions in Amotosalen/UVA-Treated Platelet Concentrates.

Background: Pathogen inactivation treatment (PIT) has been shown to alter platelet function, phenotype, morphology and to induce a faster aging of platelet concentrates (PCs). Key pieces of information are still missing to understand the impacts of PITs at the cellular level. Objectives: This study investigated the impact of amotosalen/UVA on PCs, from a post-translational modifications (PTM) point of view. Phosphoproteomic analyses were conducted on resting platelets, right after the amotosalen/UVA treatment and compared with untreated PCs. Method: A two-arm study setting was carried out to compare PIT (amotosalen/UVA) to untreated PCs, on day 1 post-donation. Based on a pool-and-split approach, 12 PCs were split into two groups (treated and untreated). Quantitative phosphoproteomics was performed using TMT technology to study the changes of phosphoproteins right after the PIT. Results: A total of 3,906 proteins and 7,334 phosphosites were identified, and 2,473 proteins and 2,214 phosphosites were observed in at least 5 to 6 replicates. Compared to untreated platelets, PIT platelets exhibited an upregulation of the phosphorylation effects, with 109 phosphosites identified with a higher than 2-fold change. Two pathways were clearly identified. The mitogen activated protein kinases (MAPKs) cascade, which triggers the granule secretion and the activation of the pS15 HSPB1. One of the shape change pathways was also observed with the inhibition of the Threonine 18 and Serine 19 phosphorylations on myosin light chain (MLC) protein after the amotosalen/UVA treatment. Conclusions: This work provides a deep insight into the impact of amotosalen/UVA treatment from a phosphoprotein viewpoint on resting platelets. Clear changes in phosphorylation of proteins belonging to different platelet pathways were quantified. This discovery corroborates previous findings and fills missing parts of the effect of photochemical treatments on platelets.

Inhibition of mitochondrial calcium transporters alters adp-induced platelet responses.

INTRODUCTION: ADP-stimulated elevation of cytosolic Ca2+ is an important effector mechanism for platelet activation. The rapidly elevating cytosolic Ca2+ is also transported to mitochondrial matrix via Mitochondrial Ca2+ Uniporter (MCU) and extruded via Na+/Ca2+/Li+ Exchanger (NCLX). However, the exact contribution of MCU and NCLX in ADP-mediated platelet responses remains incompletely understood. METHODS AND RESULTS: The present study aimed to elucidate the role of mitochondrial Ca2+ transport in ADP-stimulated platelet responses by inhibition of MCU and NCLX with mitoxantrone (MTX) and CGP37157 (CGP), respectively. As these inhibitory strategies are reported to cause distinct effects on matrix Ca2+ concentration, we hypothesized to observe opposite impact of MTX and CGP on ADP-induced platelet responses. Platelet aggregation profiling was performed by microplate-based spectrophotometery while p-selectin externalization and integrin αIIbß3 activation were analyzed by fluorescent immunolabeling using flow cytometery. Our results confirmed the expression of both MCU and NCLX mRNAs with relatively low abundance of NCLX in human platelets. In line with our hypothesis, MTX caused a dose-dependent inhibition of ADP-induced platelet aggregation without displaying any cytotoxicity. Likewise, ADP-induced p-selectin externalization and integrin αIIbß3 activation was also significantly attenuated in MTX-treated platelets. Concordantly, inhibition of NCLX with CGP yielded an accelerated ADP-stimulated platelet aggregation which was associated with an elevation of p-selectin surface expression and αIIbß3 activation. CONCLUSION: Together, these findings uncover a vital and hitherto poorly characterized role of mitochondrial Ca2+ transporters in ADP-induced platelet activation.

Ischemic Stroke in Cancer: Mechanisms, Biomarkers, and Implications for Treatment.

Ischemic stroke is an important cause of morbidity and mortality in cancer patients. The underlying mechanisms linking cancer and stroke are not completely understood. Long-standing and more recent evidence suggests that cancer-associated prothrombotic states, along with treatment-related vascular toxicity, such as with chemotherapy and immunotherapy, contribute to an increased risk of ischemic stroke in cancer patients. Novel biomarkers, including coagulation, platelet and endothelial markers, cell-free DNA, and extracellular vesicles are being investigated for their potential to improve risk stratification and patient selection for clinical trials and to help guide personalized antithrombotic strategies. Treatment of cancer-related stroke poses unique challenges, including the need to balance the risk of recurrent stroke and other thromboembolic events with that of bleeding associated with antithrombotic therapy. In addition, how and when to restart cancer treatment after stroke remains unclear. In this review, we summarize current knowledge on the mechanisms underlying ischemic stroke in cancer, propose an etiological classification system unique to cancer-related stroke to help guide patient characterization, provide an overview of promising biomarkers and their clinical utility, and discuss the current state of evidence-based management strategies for cancer-related stroke. Ultimately, a personalized approach to stroke prevention and treatment is required in cancer patients, considering both the underlying cancer biology and the individual patient's risk profile.

Diagnostic value of antibody-induced procoagulant platelets in heparin-induced thrombocytopenia: communication from the ISTH SSC Subcommittee on Platelet Immunology.

Heparin-induced thrombocytopenia (HIT) is an immune-mediated prothrombotic disorder characterized by a drop in platelet count and an increased risk of thromboembolic events. The accurate diagnosis of HIT involves clinical assessment and laboratory testing with well-characterized functional tests. Recent research has shown the potential of investigating procoagulant platelet formation induced by HIT antibodies. To successfully implement these assays in clinical laboratories, careful consideration of technical and preanalytical factors is crucial. In this communication from the SSC Platelet Immunology, we provide a consensus from experts on the use of flow cytometry in HIT diagnosis, highlighting the importance of standardized protocols.

[Hematological workup in cases of recurrent early miscarriages: what evidences?] / Bilan hématologique en cas de fausses couches précoces à répétition : quelles évidences ?

Recurrent miscarriages have a major psychological and somatic impact, as well as a significant economic burden. An etiological work-up should be offered after two or three miscarriages, the threshold varying from one scientific society to another. However, the proposed biological work-up must be justified by scientific evidence. A simple blood count, basic coagulation tests including fibrinogen assay and anti-phospholipid antibodies testing should be performed initially. Hereditary thrombophilia testing should only be carried out if there is a history of maternal thrombosis. In the event of an abnormality, management should be multidisciplinary, and the prescription of medication should follow recommended guidelines. Prophylactic treatment is not justified in the absence of a known etiology.

Les fausses couches précoces (FCP) à répétition ont un impact psychologique et somatique important, ainsi qu'un poids économique non négligeable. Un bilan étiologique devrait être proposé à partir de deux ou trois fausses couches, le seuil variant selon les sociétés savantes. Cependant, le bilan biologique doit être justifié par des évidences scientifiques. Une formule sanguine simple, des tests de coagulation de base avec le dosage du fibrinogène et une recherche d'anticorps anti-phospholipides devraient être réalisés en première intention. Une recherche de thrombophilie héréditaire ne devrait être effectuée qu'en cas d'antécédent thrombotique maternel. En cas d'anomalie, la prise en charge doit être multidisciplinaire et la prescription de médicaments doit suivre les recommandations. Un traitement prophylactique n'est pas justifié en l'absence d'étiologie retrouvée.

Anti-PF4 immunothrombosis without proximate heparin or adenovirus vector vaccine exposure.

ABSTRACT: Platelet-activating anti-platelet factor 4 (PF4)/heparin antibodies and anti-PF4 antibodies cause heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombocytopenia and thrombosis (VITT), respectively. Diagnostic and treatment considerations differ somewhat between HIT and VITT. We identified patients with thrombocytopenia and thrombosis without proximate heparin exposure or adenovirus-based vaccination who tested strongly positive by PF4/polyanion enzyme-immunoassays and negative/weakly positive by heparin-induced platelet activation (HIPA) test but strongly positive by PF4-induced platelet activation (PIPA) test (ie, VITT-like profile). We tested these patients by a standard chemiluminescence assay that detects anti-PF4/heparin antibodies found in HIT (HemosIL AcuStar HIT-IgG(PF4-H)) as well as a novel chemiluminescence assay for anti-PF4 antibodies found in VITT. Representative control sera included an exploratory anti-PF4 antibody-positive but HIPA-negative/weak cohort obtained before 2020 (n = 188). We identified 9 patients with a clinical-pathological profile of a VITT-like disorder in the absence of proximate heparin or vaccination, with a high frequency of stroke (arterial, n = 3; cerebral venous sinus thrombosis, n = 4), thrombocytopenia (median platelet count nadir, 49 × 109/L), and hypercoagulability (greatly elevated D-dimer levels). VITT-like serological features included strong reactivity by PIPA (aggregation <10 minutes in 9/9 sera) and positive testing in the novel anti-PF4 chemiluminescence assay (3/9 also tested positive in the anti-PF4/heparin chemiluminescence assay). Our exploratory cohort identified 13 additional patient sera obtained before 2020 with VITT-like anti-PF4 antibodies. Platelet-activating VITT-like anti-PF4 antibodies should be considered in patients with thrombocytopenia, thrombosis, and very high D-dimer levels, even without a proximate exposure to heparin or adenovirus vector vaccines.

Eosinophilic Granulomatosis with Polyangiitis after mRNA-1273 SARS-CoV-2 Vaccine.

During one of the worst global health crises, millions of people were vaccinated against SARS-CoV-2. In rare cases, new onset systemic inflammatory diseases were reported with temporal coincidence to the vaccination. We describe a case of severe Eosinophilic Granulomatosis with Polyangiitis (EGPA) in a young asthmatic woman, occurring after a second dose of the mRNA-1273 vaccine. She presented with multisystem EGPA with cardiac and central nervous system involvement, complicated by secondary immune thrombocytopenia (ITP). We review the reported cases of EGPA coinciding with SARS-CoV-2 mRNA vaccination. All potentially vaccine-related EGPA cases reported so far occurred within 14 days from immunization. EGPA is very rare with an incidence of 1:1,000,000 inhabitants, and the number of reported post-vaccination EGPA cases lies within the expected incidence rate for the period. While we cannot prove a causal relationship between the vaccine and EGPA onset, the temporal relationship with the vaccine immune stimulation is intriguing, in a disease occurring almost always in adults with asthma and/or chronic rhinosinusitis and driven by an aberrant Th2 lymphocyte activation with hypereosinophilia; nevertheless, cases of inflammatory diseases (IMIDs) emerging in the context of vaccination remain rare and the benefits of preventing severe COVID presentations with SARS-CoV-2 mRNA vaccines remain unquestionable.

Recommendations for the use of andexanet alfa in the management of bleeding in patients on oral factor Xa inhibitors in Switzerland: Guideline from the Working Party Hemostasis of the Swiss Society of Hematology

Anticoagulants are essential in preventing and treating thrombosis. Unfortunately, their use is accompanied by an enhanced risk of bleeding. Since the introduction of direct oral anticoagulants (DOACs), the risk of major bleeding has been reduced but not eliminated. Major bleeding events related to the use of factor Xa inhibitors can be challenging to manage. In recent years, four-factor prothrombin complex concentrates have been used in patients with severe bleeding taking oral direct factor Xa inhibitors (apixaban, edoxaban and rivaroxaban). Andexanet alfa (OndexxyaTM, AstraZeneca AG) is a specially designed recombinant version of human factor Xa that acts as a decoy receptor to reverse the effects of factor Xa inhibitors. Since 2 December 2020, andexanet alfa has been used in Switzerland for adult patients receiving apixaban or rivaroxaban when reversal of anticoagulation is required because of life-threatening or uncontrolled bleeding. However, the use of andexanet alfa remains a challenge owing to its cost, the reported thrombotic complications and the fact that its efficacy mainly relates to intracranial haemorrhage. Moreover, the use of nonspecific reversal agents together with andexanet alfa is controversial. The present recommendations on the use of andexanet alfa in the management of bleeding in patients on factor Xa inhibitors in Switzerland were developed by a group of Swiss experts from the Working Party Hemostasis of the Swiss Society of Hematology. These recommendations aim to provide support to clinicians in their decision-making in the management of patients with major bleeding receiving factor Xa inhibitors.

Determination of Anti-Xa Inhibitor Plasma Concentrations Using a Universal Edoxaban Calibrator.

A universal calibrator for the determination of all anti-Xa inhibitors would support laboratory processes. We aimed to test the clinical performance of an anti-Xa assay utilizing a universal edoxaban calibrator to determine clinically relevant concentrations of all anti-Xa inhibitors. Following a pilot study, we enrolled 553 consecutive patients taking rivaroxaban, edoxaban, or apixaban from nine study centers in a prospective cross-sectional study. The Technochrom® anti-Xa assay was conducted using the Technoview® edoxaban calibrator. Using ultra-high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), anti-Xa inhibitor drug concentrations were determined. Sensitivities and specificities to detect three clinically relevant drug concentrations (30 µgL-1, 50 µgL-1, 100 µgL-1) were determined. Overall, 300 patients treated with rivaroxaban, 221 with apixaban, and 32 with edoxaban were included. The overall correlation coefficient (rs) was 0.95 (95% CI 0.94, 0.96). An area under the receiver operating characteristic curve of 0.96 for 30 µgL-1, 0.98 for 50 µgL-1, and 0.99 for 100 µgL-1 was found. The sensitivities were 92.3% (95% CI 89.2, 94.6), 92.7% (89.4, 95.1), and 94.8% (91.1, 97.0), respectively (specificities 82.2%, 93.7%, and 94.4%). In conclusion, the clinical performance of a universal, edoxaban-calibrated anti-Xa assay was solid and most drug concentrations were predicted correctly.

Identification of High Platelet Reactivity Despite ADP P2Y 12 Inhibitor Treatment: Two Populations in the Vasodilator-Stimulated Phosphoprotein Assay and Variable PFA-P2Y Shapes of Curve.

Introduction Response to ADP P2Y 12 receptor inhibition by clopidogrel can be evaluated by various techniques. Here, we compared a functional rapid point-of-care technique (PFA-P2Y) with the degree of biochemical inhibition assessed by the VASP/P2Y 12 assay. Methods Platelet response to clopidogrel was investigated in 173 patients undergoing elective intracerebral stenting (derivation cohort n = 117; validation cohort n = 56). High platelet reactivity (HPR) was defined as PFA-P2Y occlusion time <106 seconds or VASP/P2Y 12 platelet reactivity index (PRI) >50%. Results In the derivation cohort, receiver operator characteristics analysis for the ability of PFA-P2Y to detect biochemical HPR showed high specificity (98.4%) but poor sensitivity (20.0%) and a very low area under the curve (0.59). The VASP/P2Y 12 assay revealed two coexisting platelet populations with different levels of vasodilator-stimulated phosphoprotein (VASP) phosphorylation: a fraction of highly phosphorylated, inhibited platelets and another of poorly phosphorylated, reactive platelets. Analysis of the PFA-P2Y curve shape revealed different types, categorized by time of occlusion (<106 seconds, 106 to 300 seconds, >300 seconds), and pattern (regular, irregular, and atypical). Noteworthy, curves with late occlusion and permeable curves with an irregular or atypical pattern correlated with VASP-PRI >50% and smaller sizes of the inhibited platelet subpopulation. Considering the PFA-P2Y shape of the curve for the detection of HPR improved sensitivity (72.7%) and preserved specificity (91.9%), with a rather high AUC (0.823). The validation cohort confirmed the VASP/P2Y 12 assay data and the usefulness of considering the PFA-P2Y curve shape. Conclusion In patients treated with acetylsalicylic acid and clopidogrel for 7-10 days, the VASP/P2Y 12 assay reveals two coexisting subpopulations of differentially inhibited platelets, whose relative sizes predict global PRI and distinct PFA-P2Y curve patterns, indicating incomplete clopidogrel efficacy. The detailed analysis of both VASP/P2Y 12 and PFA-P2Y is necessary for optimal detection of HPR.

Pharmacodynamics Monitoring of Emicizumab in Patients with Hemophilia A.

BACKGROUND: Emicizumab is a bispecific antibody mimicking coagulation factor VIII (FVIII) employed to treat patients with hemophilia A (PwHA) regardless of FVIII inhibitor status. The identification of biological markers reflecting the hemostatic competence of patients under emicizumab therapy would have a great clinical value. Unfortunately, emicizumab over-corrects standard coagulation assays, precluding their use for evaluating the hemostatic correction achieved in vivo. Here, we investigated whether global coagulation assays (GCA) would allow monitoring the biological response to non-factor replacement therapy with emicizumab. MATERIALS AND METHODS: Six adults PwHA received a weekly dose of emicizumab of 3 mg/kg during weeks (W) 1 4 and 1.5 mg/kg from W5 onwards. Response to treatment was monitored weekly by emicizumab plasma concentration, thrombin generation (TG), and fibrin clot formation (FCF) and structure. TG and FCF results were compared to patient baseline, FVIII replacement, and healthy donors. RESULTS: TG and FCF significantly increased in PwHA after the loading period, reaching a plateau that lasted until the end of monitoring. Similarly, fibrin clot network became denser with thinner fibrin fibers. However, TG contrary to FCF remained at the lower limits of reference values. Remarkably, despite having similar plateau concentrations of emicizumab some patients showed markedly different degrees of TG and FCF improvement. CONCLUSION: Our study enriches the knowledge on the use of GCA to monitor non-factor replacement therapy, indicating that TG and FCF could act as direct markers of emicizumab biological activity. GCA allow to capture and visualize the individually variable response to emicizumab, leading a step forward to the personalization of patient treatment.

Efficacy and Safety of Rivaroxaban for Postoperative Thromboprophylaxis in Patients After Bariatric Surgery: A Randomized Clinical Trial.

Importance: Venous thromboembolism (VTE) is a leading cause of morbidity and mortality after bariatric surgery. Clinical end point studies on thromboprophylaxis with direct oral anticoagulants in patients undergoing bariatric surgery are lacking. Objective: To assess the efficacy and safety of a prophylactic dose of 10 mg/d of rivaroxaban for both 7 and 28 days after bariatric surgery. Design, Setting, and Participants: This assessor-blinded, phase 2, multicenter randomized clinical trial was conducted from July 1, 2018, through June 30, 2021, with participants from 3 academic and nonacademic hospitals in Switzerland. Intervention: Patients were randomized 1 day after bariatric surgery to 10 mg of oral rivaroxaban for either 7 days (short prophylaxis) or 28 days (long prophylaxis). Main Outcomes and Measures: The primary efficacy outcome was the composite of deep vein thrombosis (symptomatic or asymptomatic) and pulmonary embolism within 28 days after bariatric surgery. Main safety outcomes included major bleeding, clinically relevant nonmajor bleeding, and mortality. Results: Of 300 patients, 272 (mean [SD] age, 40.0 [12.1] years; 216 women [80.3%]; mean body mass index, 42.2) were randomized; 134 received a 7-day and 135 a 28-day VTE prophylaxis course with rivaroxaban. Only 1 thromboembolic event (0.4%) occurred (asymptomatic thrombosis in a patient undergoing sleeve gastrectomy with extended prophylaxis). Major or clinically relevant nonmajor bleeding events were observed in 5 patients (1.9%): 2 in the short prophylaxis group and 3 in the long prophylaxis group. Clinically nonsignificant bleeding events were observed in 10 patients (3.7%): 3 in the short prophylaxis arm and 7 in the long prophylaxis arm. Conclusions and Relevance: In this randomized clinical trial, once-daily VTE prophylaxis with 10 mg of rivaroxaban was effective and safe in the early postoperative phase after bariatric surgery in both the short and long prophylaxis groups. Trial Registration: ClinicalTrials.gov Identifier: NCT03522259.