Thrombocytopenia is a common adverse effect of chemotherapy. The development of chemotherapy-induced thrombocytopenia (CIT) is influenced by cancer type and therapy, occurring in approximately one-third of patients with a solid tumor diagnosis and half of all patients with a hematologic malignancy. CIT may complicate the administration of chemotherapy, leading to therapeutic delays or dose reductions. This guidance document, presented by the International Society on Thrombosis and Haemostasis (ISTH) Subcommittee on Hemostasis and Malignancy, provides a comprehensive summary of the evidence and offers direction on the use of thrombopoietin receptor agonists (TPO-RAs) in various settings of CIT, including solid tumors, acute myeloid leukemia, stem cell transplant, and lymphoma. Studies have shown that TPO-RAs can improve platelet counts in CIT, but the clinical benefits of TPO-RA in terms of reducing bleeding, limiting platelet transfusion, avoiding chemotherapy delay, or dose reduction are uncertain. Further research is needed to optimize the selection of appropriate indications and study design to manage thrombocytopenia following chemotherapy.

Introduction: Given the great variability of the individual response to SARS-CoV2 infection, it is important to understand whether and how biological and genetic factors might predispose to the infection and to the degree of severity, including the development of systemic coagulopathy and thrombosis. In this study, we evaluated the frequency of prothrombotic allelic variants (AVs) in coagulation genes in a population of COVID-19 patients, to verify whether these polymorphisms, alone or in combination, are associated to an increased susceptibility to develop COVID-19 and/or a greater severity. Methods: A cohort of 358 patients (257M/101F; median age: 55 years) from the Bergamo area with two different degrees of COVID-19 severity, i.e., severe disease (hospitalized, n=212) or mild disease (non-hospitalized, n=146), was enrolled from April 2020 to June 2021 and followed-up for disease outcome and thrombosis. A cohort of 377 healthy subjects (177M/200F; median age: 49 years) from the same area without COVID-19 acted as a control group. DNA was analyzed for a panel of prothrombotic/inflammatory single nucleotide polymorphisms (SNPs) including FII rs1799963, FV rs6025, FV rs118203907, FXIIIA1 rs5985, FGB rs1800790, MTHFR rs1801131 and MTHFR rs1801133 as well as two SNPs located in the coding region of angiotensin-converting enzyme (ACE2) gene, namely ACE2 rs140312271 and ACE2 rs41303171. Statistical analysis was performed using SPSS statistical software. Results: Among the AVs analyzed, the rs6025 polymorphism of FV gene (FV Leiden) was more frequent in COVID-19 patients than in the control group. By a logistic regression corrected for age and gender, FV Leiden was associated with a 3-fold risk of developing COVID-19 (OR: 3.2 [95% CI 1.02-10]). In contrast, the rs41303171 polymorphism of the ACE2 gene was more frequent in the control group and was a protective factor for COVID-19 (OR: 0.12 [95% CI 0.02-0.99]) even after correction for age and gender. No significant differences appeared in the frequency of the other SNPs alone or in combination. Within the COVID-19 patient cohort, the rs1801131 SNP of MTHFR gene was associated with less severe COVID-19 disease. In the hospitalized severe cohort, 17 (8%) patients developed an overt venous thromboembolic event, and 7 COVID-19-related deaths (4%) were recorded. No significant associations were found between any of the AVs analyzed and the outcomes of thrombosis and death. However, the analyses of circulating biomarkers of clotting (i.e. D-dimer, FVIII, fibrinogen, prothrombin fragment 1+2 [F1+2], and FXIII), fibrinolysis (i.e. tissue plasminogen activator [tPA], and plasminogen activator inhibitor-1 [PAI-1]) and endothelial cell activation (i.e. thrombomodulin [TM], and von Willebrand Factor [vWF]), and the neutrophil-to-lymphocyte ratio (NLR) as an inflammatory biomarker revealed thathaving fibrinogen (OR: 4.9 [95% CI 1.04-23.1]), vWF:Ag (OR: 11.8 [95% CI 2.1-66.9]) and NLR (OR: 26.1 [95% CI 2.9-237] levels above the 75th percentile was significantly associated with death. Of interest, in the same hospitalized patient group, but not in the control group, the presence of FXIII SNPs was significantly associated with high levels of F1+2. Conclusions: Our study shows that the FV Leiden polymorphism predisposes to COVID-19 infection, while the rs41303171 ACE2 polymorphism has a protective role. In addition, the rs1801131 SNP of gene MTHFR correlates with a milder COVID-19 disease. In patients with severe COVID-19, the inflammatory marker NLR, and the circulating hemostatic proteins vWF and fibrinogen are associated with mortality.

A syndrome occurring after adenoviral vector anti-SARS-CoV-2 vaccination, characterized by thrombocytopenia, venous thrombosis, and circulating anti-PF4 antibodies, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), is well described. Data on the long-term course of this syndrome are lacking. Our aim is to report the clinical and laboratory features of a patient with VITT from diagnosis and during 21 months of follow-up. Cerebral venous thrombosis associated with elevated D-dimer, low fibrinogen, thrombocytopenia, and anti-PF4 antibodies positivity occurred in this patient after ChAdOx1 nCoV-19 vaccination. Cerebral thrombosis required a revascularization procedure and decompressive craniectomy. Upon dexamethasone and anticoagulant treatment initiation, the platelet count recovered. However, a persistently high anti-PF4 antibody titer, without thrombosis recurrence, was observed. Little is known about the long-term persistence of anti-PF4 antibodies, their clinical significance, and their possible role in guiding therapeutic decisions. In our patient, we decided to continue anticoagulant treatment beyond 21 months with parallel anti-PF4 antibody monitoring.

With ageing of the population, both the risks of cardiovascular disease (CVD) and cancer are increasing worldwide, and the risk factors (e.g. obesity, diabetes) are often shared between the two conditions. Thus, more subjects will also develop the two illnesses concurrently [...].

PURPOSE:To conduct an update of the ASCO venous thromboembolism (VTE) guideline. METHODS:After publication of potentially practice-changing clinical trials, identified through ASCO's signals approach to updating, an updated systematic review was performed for two guideline questions: perioperative thromboprophylaxis and treatment of VTE. PubMed and the Cochrane Library were searched for randomized controlled trials (RCTs) published between November 1, 2018, and June 6, 2022. RESULTS:Five RCTs provided information that contributed to changes to the 2019 recommendations. Two RCTs addressed direct factor Xa inhibitors (either rivaroxaban or apixaban) for extended thromboprophylaxis after surgery. Each of these postoperative trials had important limitations but suggested that these two oral anticoagulants are safe and effective in the settings studied. An additional three RCTs addressed apixaban in the setting of VTE treatment. Apixaban was effective in reducing the risk of recurrent VTE, with a low risk of major bleeding. RECOMMENDATIONS:Apixaban and rivaroxaban were added as options for extended pharmacologic thromboprophylaxis after cancer surgery, with a weak strength of recommendation. Apixaban was also added as an option for the treatment of VTE, with high quality of evidence and a strong recommendation.Additional information is available at www.asco.org/supportive-care-guidelines.

Thrombosis is a common complication of advanced cancer, yet the cellular mechanisms linking malignancy to thrombosis are poorly understood. The unfolded protein response (UPR) is an ER stress response associated with advanced cancers. A proteomic evaluation of plasma from patients with gastric and non-small cell lung cancer who were monitored prospectively for venous thromboembolism demonstrated increased levels of UPR-related markers in plasma of patients who developed clots compared with those who did not. Release of procoagulant activity into supernatants of gastric, lung, and pancreatic cancer cells was enhanced by UPR induction and blocked by antagonists of the UPR receptors inositol-requiring enzyme 1α (IRE1α) and protein kinase RNA-like endoplasmic reticulum kinase (PERK). Release of extracellular vesicles bearing tissue factor (EVTFs) from pancreatic cancer cells was inhibited by siRNA-mediated knockdown of IRE1α/XBP1 or PERK pathways. Induction of UPR did not increase tissue factor (TF) synthesis, but rather stimulated localization of TF to the cell surface. UPR-induced TF delivery to EVTFs was inhibited by ADP-ribosylation factor 1 knockdown or GBF1 antagonism, verifying the role of vesicular trafficking. Our findings show that UPR activation resulted in increased vesicular trafficking leading to release of prothrombotic EVTFs, thus providing a mechanistic link between ER stress and cancer-associated thrombosis.

Topic: 34. Thrombosis and vascular biology - Biology & Translational Research Background: VTE is a common complication in lung cancer patients and is associated with an increased mortality. The tight and reciprocal interaction between cancer and hemostasis led us to investigate the role of hemostatic biomarkers in the prediction of cancer associated thrombosis. Aims: In a large prospective cohort of metastatic lung cancer patients, we assessed whether hemostatic biomarkers and TG can predict for VTE and mortality within the first 6 months after diagnosis (HYPERCAN study, Clinical Trials.gov ID# NCT02622815). The Khorana risk score (KRS), a validated VTE risk prediction model, was also utilized to assess the VTE risk and mortality in the same cohort of patients. Methods: 568 newly diagnosed patients with metastatic lung cancer, and a median age of 65 years (range: 34-88) were studied. Platelet-free plasma samples were tested for factor VIII (FVIII), D-dimer, fibrinogen, prothrombin fragment 1 + 2 [F1 + 2], proteins C and S, and TG by the calibrated automated thrombogram at 5pM tissue factor (TF). Clinical data were recorded at enrollment, VTE and death were monitored during follow-up. Results: During follow-up, 63 patients experienced a VTE, which consisted of 30 isolated pulmonary embolism (PE), 27 deep vein thrombosis (DVT), and 9 PE + DVT, providing a 6-months cumulative incidence of 12% (11-18). Patients who developed a VTE during follow-up were characterized by increased baseline levels of D-dimer (p=0.002), FVIII (p=0.007), F1 + 2 (0.002) and peak of TG (p=0.002), as well as shorter lag time and time to peak (p<0.05) of TG, compared with patients without VTE. The remaining hemostatic parameters were similar between the two groups. During the same follow-up, 158 deaths occurred, with a cumulative incidence of 31% (27-35). By competitive multivariate Fine–Gray proportional hazard regression model (with death as competing risk), D-dimer, F1 + 2 levels, and peak of TG were identified as independent risk factors (p<0.05) for VTE. Based on the sub-distribution HR of the 3 biomarkers, we generated a continuous risk-score for the prediction of VTE. By ROC analysis, a value of 850 was identified as the best cut-off of the score (AUC 0.648, p= 0.001) for the stratification of patients in a high and a low-risk category of VTE. According to this cut-off, the cumulative incidence of VTE was 5.8% (0.32-12.9) in the low-risk group, and 14% (12-20) in the high-risk group. No significant stratification of patients in different VTE risk categories was obtained by the application of the KRS. Differently, the KRS significantly stratified the patients at different risk of death, providing cumulative incidences of 22%, 32%, and 49% in the low-, intermediate-, and high-risk categories, respectively (p<0.05), and of 22% vs 37% (p<0.001) in the low- vs high-risk group by the single 2-point cut-off value. Finally, we found that VTE occurrence was associated with a higher risk of death (VTE vs no VTE: 42 vs 28%; log-rank <0.001). Summary/Conclusion: Our data show the important contribution of hemostatic biomarkers in the identification of metastatic lung cancer patients at higher risk of VTE, where the KRS failed to provide significant results. In addition, our study provides evidence that cancer patients with VTE had significantly lower survival rates than those without and identifies the predictive ability of the KRS for mortality in patients with lung cancer. Keywords: Hypercoagulation, Venous thromboembolism, Lung cancer, D-dimer

BackgroundPatients with cancer are commonly characterized by abnormalities in laboratory coagulation tests, underlying a subclinical hypercoagulable condition. Due to the involvement of the hemostatic system in cancer patients, some of its biomarkers, such as fibrinogen, could be a useful tool in predicting cancer risk. We performed a case-cohort study to evaluate the relationship among fibrinogen levels and colorectal cancer (CRC).MethodsIn the framework of Moli-sani Study (N = 24,325, enrolled 2005–2010) a subcohort of 1,290 individuals (55.0% women; mean age 55.0 ± 12.0 years) was selected and compared with 126 CRC cases identified during a follow-up of 4.3 years. Incident cases of colorectal cancer were ascertained by direct linkage with hospital discharge forms according to the International Classification of Disease (ICD-9-CM) codes: 153–154. Events were validated through medical records and confirmed by histological reports. Fibrinogen levels were measured in frozen citrated plasma samples. Hazard Ratio (HR) and 95% confidence interval (CI), adjusted by relevant covariates were estimated by a Cox regression model using Prentice method.ResultsIndividuals with levels of fibrinogen ≥400 mg/dL had a higher hazard to develop colorectal cancer when compared to those with lower levels after adjustment for sex and age (HR: 1.81; 95% CI 1.12–2.92). Additional adjustment for CRC family history, income, physical activity, diabetes medication and hypercholesterolemia did not modify the result (HR: 1.91; 95% CI 1.15–3.17). Analyses stratified by age and sex showed a most evident association in elderly (HR: 2.30; 95% CI: 1.10–4.81) and in women (HR: 2.28; 95% CI: 1.08–4.81). Sensitivity analyses confirmed the main findings, showing independence from a potential role of confounding by a large panel of biomarkers, including inflammation and hemostasis factors.ConclusionOur results, based on a case-cohort study from a general adult population apparently free from any cancer during the recruitment, showed that fibrinogen levels ≥400 mg/dL were positively and independently associated with CRC, suggesting that this glycoprotein could be a potential biomarker for this type of cancer and supporting the “common soil hypothesis” in the pathophysiology of cardiovascular disease and tumors.

In malignant diseases, the development of a systemic hypercoagulable state is the consequence of the procoagulant activity of cancer cells on the hemostatic system and based on this close relationship, alterations in the levels of hemostatic biomarkers and/or biomarkers of blood clotting activation are under investigation as a potential tool in predicting for different cancer outcomes. Today, breast cancer remains the most common tumor and the second cause of mortality for cancer in women. There is still a need for novel biomarkers for making a diagnosis at a very early stage of disease and for the classification of individuals at different risks of disease recurrence or progression. In this review, we will discuss the pathogenesis of the thrombophilic state in breast cancer patients and its interconnection with the mechanisms of malignant progression, and report on the latest results from the HYPERCAN study in the context of hemostatic biomarker development in the breast cancer setting.

Introduction: The efficacy and safety of direct oral anticoagulants (DOACs) as treatment alternatives for patients with thrombotic antiphospholipid syndrome (APS) remain controversial. Methods: We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) that compared the efficacy and safety of DOACs with vitamin-K antagonists (VKAs) in patients with thrombotic APS. We searched PubMed, EMBASE and Cochrane Central Register of Controlled Trials through April 9, 2022. Main efficacy outcomes were a composite of arterial thrombotic events, and a composite of venous thromboembolic events (VTE). The main safety outcome was major bleeding according to the International Society on Thrombosis and Hemostasis (ISTH) criteria. A random effects model with inverse variance was used for the primary analysis. Risk of bias was assessed using the Cochrane Collaboration criteria. Results: Our search retrieved 253 studies. Four RCTs involving 474 patients were included (Figure). All four RCTs were open-label but had proper random sequence generation and adequate allocation concealment. The DOACs used were rivaroxaban (3 trials) and apixaban (1 trial). The mean percent time in therapeutic range in the warfarin arm among the four studies was 60%. Overall, use of DOACs compared with VKAs was associated with increased odds of composite of arterial thrombotic events (OR 5.64, 95% confidence interval [CI] 1.96-16.27, p =0.001, I 2 = 0%). The odds of subsequent VTE events (OR 1.19, 95% CI 0.31-4.53, p =0.80, I 2 = 0%), or major bleeding (OR 1.02, 95% CI 0.42-2.47, p =0.97, I 2 = 0%) were not significantly different between the two groups. Conclusions: Patients with thrombotic APS randomized to DOACs compared to VKAs appear to have increased risk for arterial thrombosis. No significant differences were observed between patients randomized to DOACs vs VKAs in the risk of subsequent VTE or major bleeding.

Patients with cancer have an increased risk of thrombosis requiring anticoagulants and/or antiplatelet agents, and they can also encounter thrombocytopenia due to cancer itself or cancer therapies. They often undergo many procedures such as tissue or bone marrow biopsies, placement of central access lines, diagnostic or therapeutic draining procedures, lumbar puncture, and more. Management of antithrombotic agents or thrombocytopenia around the time of these procedures is highly variable. In this document, the Hemostasis and Malignancy Subcommittee of the International Society on Thrombosis and Haemostasis aims to provide useful practice guidance in the management of antithrombotic agents and thrombocytopenia around the time of common procedures in patients with cancer.

In cancer patients, thrombocytopenia can result from bone marrow infiltration or from anticancer medications and represents an important limitation for the use of antithrombotic treatments, including anticoagulant, antiplatelet, and fibrinolytic agents. These drugs are often required for prevention or treatment of cancer-associated thrombosis or for cardioembolic prevention in atrial fibrillation in an increasingly older cancer population. Data indicate that cancer remains an independent risk factor for thrombosis even in case of thrombocytopenia, since mild-to-moderate thrombocytopenia does not protect against arterial or venous thrombosis. In addition, cancer patients are at increased risk of antithrombotic drug-associated bleeding, further complicated by thrombocytopenia and acquired hemostatic defects. Furthermore, some anticancer treatments are associated with increased thrombotic risk and may generate interactions affecting the effectiveness or safety of antithrombotic drugs. In this complex scenario, the European Hematology Association in collaboration with the European Society of Cardiology has produced this scientific document to provide a clinical practice guideline to help clinicians in the management of patients with cancer and thrombocytopenia. The Guidelines focus on adult patients with active cancer and a clear indication for anticoagulation, single or dual antiplatelet therapy, their combination, or reperfusion therapy, who have concurrent thrombocytopenia because of either malignancy or anticancer medications. The level of evidence and the strength of the recommendations were discussed according to a Delphi procedure and graded according to the Oxford Centre for Evidence-Based Medicine.

INTRODUCTION: Passive immunization therapy with convalescent plasma has been successfully used in prior viral pandemics. For these reasons, from the beginning of the COVID-19 outbreak in March 2020, our hospital has been actively involved in the collection of COVID-19 convalescent plasma (CCP) and its administration to hospitalized COVID-19 patients. We set up a registry to collect prospectively clinical and laboratory data, and blood samples, from CCP donors and CCP recipients (IMMUNOCOVID registry, clinicaltrials.gov identifier #04614012, approved by the local Ethics Committee). In the present study, in a cohort of COVID-19 plasma recipients, we prospectively assessed the effect of CCP treatment on different clinical and laboratory parameters, including anti-SARS-CoV2 IgG antibody (Ab) levels, inflammatory and coagulation biomarkers. METHODS: Hospitalized COVID-19 patients were treated with maximum 3 CCP units (200 ml/unit), each given every other day, and followed-up clinically for 30 days after first CCP infusion. Venous blood samples were collected on days 0 (D0), 3 (D3), and 5 (D5) before each CCP administration, and on day 7 (D7) after the first administration. The following laboratory measurements were performed: IgG anti-SARS-CoV2 Nucleocapsid protein (anti-N) and IgG anti-Spike protein (anti-S) Ab (quantitative assay); fibrinogen, D-dimer, C reactive protein (CRP), procalcitonin, LDH, Hb, blood cell counts, AST, ALT, creatinine, and GFR. Results are expressed as median and 5th-95th percentile range. RESULTS: From May 2020 to April 2022, 334 (103F/231M) hospitalized COVID-19 patients received CCP treatment. The median age of the cohort was 67 (41-86) years; 89 were admitted to the intensive care unit (ICU) and 245 were in the medical general ward (non-ICU patients). Among this cohort, 255 patients received 3 CCP units, 47 patients 2 CCP units, and 32 only 1 CCP unit. The median time from hospital admission to CCP infusion was 2 days (0 - 70) and a total of 890 CCP units were infused with a median value of 153 AU/ml (100-400) anti-S IgG Ab. Treatment with CCP led to a significant (p<0.001) 7.1-fold increase in anti-S and 1.7-fold increase in anti-N Ab at day 7. By multivariate analysis, the percentage increase in anti-S Ab [i.e., delta = (D7-D0/D0)] was significantly (p<0.05) associated with younger age (beta=-0.181) and male gender (beta=-0.195), but not with disease severity (ICU vs non-ICU), with the highest increment occurring in males <60 years (9.8-fold). Regarding inflammatory and coagulation biomarkers, at enrollment, CRP, neutrophil count, LDH, procalcitonin, fibrinogen and D-dimer levels were all significantly elevated, while lymphocytes and Hb were significantly lower than the normal range. Compared to non-ICU patients, the ICU group, at D0, had higher levels (p<0.05) of inflammatory biomarkers and D-dimer, and significantly lower (p<0.05) lymphocyte count, Hb, and fibrinogen level. In the subgroup of 255 patients who received 3 CCP infusions, in parallel to anti-SARS-CoV2 IgG increment, a significant (p<0.001) reduction in CRP, LDH, ferritin, procalcitonin, and fibrinogen levels occurred. This was particularly apparent in the non-ICU subgroup. Among the whole cohort of 334 patients, 66 had cancer (28 hematological tumors, 33 solid tumors, and 5 both hematological and solid tumors). The median age of this subgroup was 70 years (49-88), with 16 of them admitted to ICU. In this category of patients, a significant increase (p<0.01) of both anti-S (4.7-fold) and anti-N (1.3-fold) IgG occurred, not differently from the rest of patients. Four out of 890 CCP infusions were associated with a mild adverse event with a resolution in 24 hours. Regarding overall mortality, 48 patients (14%) died after 30 days follow-up [15F/33M, median age 64 years (40-81)], 16 of them were in ICU. CONCLUSIONS: In our study, CCP treatment leads to an increase in antibody levels in the recipients, particularly in males <60 years. This occurs also in subjects with cancer and those with severe COVID-19. Notably, the increase of humoral immune response is associated with a decrease in inflammatory parameters and fibrinogen levels. The low incidence of adverse events observed supports the safety of CCP administration.

IntroductionIn a prospective cohort of hospitalized COVID-19 patients, an extensive characterization of hemostatic alterations by both global and specific assays was performed to clarify mechanisms underlying the coagulopathy and identify predictive factors for thrombotic and hemorrhagic events during hospitalization. Materials and MethodsIntensive care unit (ICU; n = 46) and non-ICU (n = 55) patients were enrolled, and the occurrence of thrombotic and hemorrhagic events was prospectively monitored. At study inclusion, thromboelastometry together with the measurement of specific coagulation proteins and hypercoagulation markers was performed. ResultsPatients (median age 67 years) showed significantly shorter clot formation time together with greater maximum clot firmness by thromboelastometry, increased levels of F1 + 2 and D-dimer, as biomarkers of hypercoagulability, and of procoagulant factors V, VIII, IX, XI, and fibrinogen, while FXIII was significantly reduced. The concentration of fibrinolytic proteins, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) were elevated in the overall cohort of patients. Many of these hemostatic alterations were significantly greater in ICU compared to non-ICU subjects and, furthermore, they were associated with inflammatory biomarker elevation [i.e., interleukin 6 (IL-6), C-reactive protein (CRP), neutrophil to lymphocyte ratio (NLR), and procalcitonin]. After enrollment, 7 thrombosis and 14 major bleedings occurred. Analysis of clinical and biological data identified increased t-PA, PAI-1, and NLR values as independent predictive factors for thrombosis, while lower FXIII levels were associated with bleeding. ConclusionThis study demonstrates alterations in all different hemostatic compartments analyzed, particularly in severe COVID-19 conditions, that strongly correlated with the inflammatory status. A potential role of fibrinolytic proteins together with NLR and of FXIII as predictors of thrombotic and hemorrhagic complications, respectively, is highlighted.

Introduction: Hypercoagulability, thrombosis and microvascular dysfunction are hallmarks of the Philadelphia chromosome-negative myeloproliferative neoplasms (MPN). Elevated peripheral blood cell counts appear to contribute to thrombotic risk but the precise underlying mechanisms remain to be fully elucidated. The interplay between haemostatic and pro-inflammatory pathway activity ('thrombo-inflammation') has emerged in recent years as a source of hypercoagulability in MPN. Platelets are recognised as being mediators of thrombo-inflammation in other diseases and may also be effectors of pro-inflammatory/pro-coagulant activity in MPN. We hypothesized that the platelet proteome is altered in MPN and that its characterisation would reveal insights into the pathophysiology of the disease and the associated thrombotic risk. Aim: To determine if differences exist in the pattern of platelet protein expression in patients with polycythaemia vera (PV) and essential thrombocythaemia (ET) in contrast to healthy donors. Methods: 62 patients (ET, n=38; PV, n=24) and 9 healthy volunteers were recruited at Papa Giovanni XXIII Hospital, Bergamo, Italy and the Mater Misericordiae University hospital, Dublin, Ireland. Platelets were isolated from platelet rich plasma, washed in Krebs Ringer buffer and resuspended at 1x 109 platelets/mL in phosphate buffered saline. Whole platelets were lysed in RIPA buffer and differential proteomic signatures established using label-free quantification (LFQ) mass spectrometry (MS), where platelet lysate proteins were double digested using the commercially available PreOmics kit and analysed in a Bruker TimsTOF mass spectrometer connected to a EvoSep liquid chromatography system. Identified peptides were searched against a human FASTA using MaxQuant. For statistical analysis, proteins identified in a minimum of 70% of samples in at least one group were included. Differences in protein expression were determined using an unpaired t-test with a false discovery rate of 5% and a minimal fold change of 0.1 within the Perseus software; p- values below 0.05 were considered significant. Results: 2,180 proteins from platelet lysates were quantified across all patient and control samples. In MPN platelet lysates, 49 proteins were found to be differentially expressed in comparison to controls (p< 0.05) (Figure 1), including increased expression of markers of platelet activity such as vesicle-associated membrane protein 7 (VAMP-7; regulator of granule exocytosis and actin cytoskeleton activity) and CD109 (a GPI-linked glycoprotein expressed by activated platelets). Bioinformatical analysis revealed a cohort of mitochondrial, cytoskeletal & ribosomal proteins as well as potential effectors of thrombopoiesis and thrombo-inflammation which were significantly upregulated in the MPN cohort. Strikingly, protein disulfide-isomerase (PDI, a member of the thioredoxin superfamily of redox proteins) was increased in MPN lysates. PDI has been shown to contribute to thrombosis, platelet activation and platelet-neutrophil interactions in vivo; plasma levels of PDI have been shown to be increased in MPN and are associated with thrombosis risk. Conclusion: The platelet proteome is altered in MPN and is suggestive of an activated platelet phenotype with over-expression of proteins with known pro-coagulant activity. To our knowledge the over expression of PDI in MPN platelets has not previously been described. The identification of differentially expressed proteins, such as PDI, provides mechanistic insights into the pathophysiology underlying the substantial burden of arterial and venous thrombosis in MPN and may also assist in the identification of novel therapeutic targets. Additional proteomic analysis of platelet releasate and plasma extracellular vesicles is currently ongoing and may provide additional pathophysiological insights. Figure 1: Volcano plot of MPN versus control platelet lysate proteomes (x-axis, t-test difference between the mean log2 of the LFQ values; y-axis, the negative log transformed p-value) representing the proteins significantly altered in MPN. Black hyperbolic curves show the threshold for statistical significance. 36 proteins were found to be increased in MPN platelet lysates (including CD109, PDIA4 and VAMP-7) in comparison to control lysates (red) while 13 proteins were decreased in MPN platelet lysates (blue). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Managing anticoagulation in hematological malignancy patients with atrial fibrillation and thrombocytopenia is a clinical challenge with limited data. We aimed to identify anticoagulation management strategies and evaluate bleeding and thrombosis rates associated with each approach. A retrospective cohort study in Israel and the Netherlands was conducted. Patients with hematological malignancy and atrial fibrillation were indexed when platelets were < 50 × 109/L and followed for 30 days. The cohort included 61 patients of whom 42 (69%) had anticoagulation held at index. On multivariate analysis, holding anticoagulation was associated with age < 65 years and atrial fibrillation diagnosed within 30 days prior index. Clinically relevant bleeding was diagnosed in 7 (16.7%) and 1 (5.3%) of patients who had anticoagulation held and continued respectively, while arterial thromboembolism occurred in 1 patient in each group (2.4% and 5.3%, respectively). All-cause mortality rate was high at 45%. Accordingly, the 30-day bleeding risk may outweigh the risk of arterial thromboembolism in hematological malignancy, platelets < 50 × 109/L and atrial fibrillation.

HLA‐C*14:125 allele is identical to HLA‐C*14:02:01:01 except for a single nonsynonymous mutation C199T.