A prospective diagnostic accuracy study evaluating rotational thromboelastometry and thromboelastography in 100 patients with von Willebrand disease

Monitoring Hemostatic Function during Cardiac Surgery with Point-of-Care Viscoelastic Assays: A Narrative Review

Bleeding is a well-known and severe complication of cardiac surgery. Cardiopulmonary bypass, along with heparinization and hemodilution, is thought to affect all pathways of the hemostatic process, leading to excessive bleeding and worsened morbidity and mortality. The traditionally used standard laboratory tests (SLTs) were not designed for the surgical setting, have long turnaround times, and are poor predictors of bleeding. This review aims to give an overview of viscoelastic assays (VEAs), compare VEAs to conventional testing methods, and summarize the evidence for VEAs in cardiac surgery. A search of Medline via Pubmed, Scopus, and Embase yielded 2,868 papers, which we reviewed and summarized the key findings. VEAs such as rotational thromboelastometry and thromboelastography provide a quick turnaround, graphical, global impression of hemostasis in whole blood. VEAs allow for the analysis of specific contributors to the coagulation process and may facilitate cause-oriented hemostatic treatment and the development of treatment algorithms. VEAs have been found to have a high specificity and high negative predictive value for coagulopathic bleeding. Patients treated with VEA-based algorithms have been shown to have lower rates of bleeding, transfusion requirements, and exposure to allogeneic blood products. However, VEA-based algorithms have not demonstrated a mortality benefit and evidence for outcomes such as surgical re-exploration and hospital length of stay remains equivocal. In conclusion, VEAs have been shown to be comparable if not superior to SLTs in cardiac surgery. Further large-scale studies are needed to better evaluate the impact of VEAs on clinical outcomes.

Utility of Global Hemostatic Assays in Patients with Bleeding Disorders of Unknown Cause

Bleeding disorder of unknown cause (BDUC) is a diagnosis of exclusion after exhaustive evaluation of plasmatic coagulation and platelet function. This review explores the utility of global hemostatic assays as confirmatory tests and in elucidating the pathophysiology of BDUC. Unlike traditional hemostatic tests that focus on coagulation factors, global assays are conducted both in plasma and also whole blood. These assays provide a more comprehensive understanding of the cell-based model of coagulation, aid in the identification of plasmatic factor abnormalities that may reduce hemostatic capacity, and allow for the assessment of impaired platelet-endothelial interactions under shear stress, as well as hyperfibrinolytic states. While clinical tests such as skin bleeding time and global assays such as PFA-100 exhibit limited diagnostic capacity, the role of viscoelastic testing in identifying hemostatic dysfunction in patients with BDUC remains unclear. Thrombin generation assays have shown variable results in BDUC patients; some studies demonstrate differences compared with healthy controls or reference values, whereas others question its clinical utility. Fibrinolysis assessment in vitro remains challenging, with studies employing euglobulin clot lysis time, plasma clot lysis time, and fluorogenic plasmin generation yielding inconclusive or conflicting results. Notably, recent studies suggest that microfluidic analysis unveils shear-dependent platelet function defects in BDUC patients, undetected by conventional platelet function assays. Overall, global assays might be helpful for exploring underlying hemostatic impairments, when conventional hemostatic laboratory tests yield no results. However, due to limited data and/or discrepant results, further research is needed to evaluate the utility of global assays as screening tools.

Point-of-Care Testing in Patients with Hereditary Disorders of Primary Hemostasis: A Narrative Review

Inherited disorders of primary hemostasis, such as von Willebrand disease and congenital platelet disorders, can cause extensive, typically mucocutaneous bleeding. Assays to diagnose and monitor these disorders, such as von Willebrand factor activity assays and light transmission aggregometry, are performed in specialized hemostasis laboratories but are commonly not available in local hospitals. Due to the complexity and relative scarcity of these conventional assays, point-of-care tests (POCT) might be an attractive alternative in patients with hereditary bleeding disorders. POCTs, such as thromboelastography, are increasingly used to assess hemostasis in patients with acquired hemostatic defects, aiding clinical decision-making in critical situations, such as during surgery or childbirth. In comparison, the use of these assays in patients with hereditary hemostasis defects remains relatively unexplored. This review aims to give an overview of point-of-care hemostasis tests in patients with hereditary disorders of primary hemostasis. A summary of the literature reporting on the performance of currently available and experimental POCTs in these disorders is given, and the potential utility of the assays in various use scenarios is discussed. Altogether, the studies included in this review reveal that several POCTs are capable of identifying and monitoring severe defects in the primary hemostasis, while a POCT that can reliably detect milder defects of primary hemostasis is currently lacking. A better understanding of the strengths and limitations of POCTs in assessing hereditary defects of primary hemostasis is needed, after which these tests may become available for clinical practice, potentially targeting a large group of patients with milder defects of primary hemostasis.

Early Goal-Directed Hemostatic Therapy for Severe Acute Bleeding Management in the Intensive Care Unit: A Narrative Review

This is a narrative review of the published evidence for bleeding management in critically ill patients in different clinical settings in the intensive care unit (ICU). We aimed to describe "The Ten Steps" approach to early goal-directed hemostatic therapy (EGDHT) using point-of-care testing (POCT), coagulation factor concentrates, and hemostatic drugs, according to the individual needs of each patient. We searched National Library of Medicine, MEDLINE for publications relevant to management of critical ill bleeding patients in different settings in the ICU. Bibliographies of included articles were also searched to identify additional relevant studies. English-language systematic reviews, meta-analyses, randomized trials, observational studies, and case reports were reviewed. Data related to study methodology, patient population, bleeding management strategy, and clinical outcomes were qualitatively evaluated. According to systematic reviews and meta-analyses, EGDHT guided by viscoelastic testing (VET) has been associated with a reduction in transfusion utilization, improved morbidity and outcome in patients with active bleeding. Furthermore, literature data showed an increased risk of severe adverse events and poor clinical outcomes with inappropriate prophylactic uses of blood components to correct altered conventional coagulation tests (CCTs). Finally, prospective, randomized, controlled trials point to the role of goal-directed fibrinogen substitution to reduce bleeding and the amount of red blood cell (RBC) transfusion with the potential to decrease mortality. In conclusion, severe acute bleeding management in the ICU is still a major challenge for intensive care physicians. The organized and sequential approach to the bleeding patient, guided by POCT allows for rapid and effective bleeding control, through the rational use of blood components and hemostatic drugs, since VET can identify specific coagulation disorders in real time, guiding hemostatic therapy with coagulation factor concentrates and hemostatic drugs with individual goals.

Diagnostic value of clot formation parameters determined by rotational thromboelastometry in 63 patients with congenital dysfibrinogenemia

Rotational thromboelastometry (ROTEM) is a global hemostasis assay. The diagnosis added value of ROTEM in congenital dysfibrinogenemia remains to be established. The aim of this study was to analyze clot formation by ROTEM in a cohort of dysfibrinogenemic patients and to establish correlations with genotype, clinical features, and coagulation parameters. The study included genetically confirmed congenital dysfibrinogenemia cases (n = 63) and healthy controls ( n  = 50). EXTEM, INTEM, FIBTEM tests were used to measure ROTEM parameters, that is, clotting time (CT), clot formation time (CFT), maximal clot firmness (MCF) and amplitude 10 min after CT (A10). The ISTH bleeding assessment tool was used to determine bleeding episodes. CT (INTEM) was statistically significantly shorter in congenital dysfibrinogenemia patients compared to controls while CFT (EXTEM) was prolonged. Patients's MCF in EXTEM, INTEM, and FIBTEM were similar to controls while A10 (FIBTEM) was statistically significantly lower. Fibrinogen activity was positively correlated with fibrinogen antigen, A10 and MCF in all three assays. Bleeding phenotypes were observed in 23 (36.5%) patients. Only CFT in EXTEM and CT in INTEM were statistically different in patients with bleeding phenotype versus controls. Carriers of the FGA mutation p.Arg35His had a CT (EXTEM) slightly prolonged and a reduced A10 (FIBTEM) compared to controls. Some ROTEM parameters were able to distinguish congenital dysfibrinogenemia patients from controls, and patients with a bleeding phenotype. Prolonged CFT in EXTEM were associated with congenital dysfibrinogenemia and bleeding phenotype. Bleeding episodes in most patients were generally mild and prevalence of thrombosis was very low.

The role of viscoelastic hemostatic assays for postpartum hemorrhage management and bedside intrapartum care

Viscoelastic hemostatic assays are point-of-care devices that assess coagulation and fibrinolysis in whole blood samples. These technologies provide numeric and visual information of clot initiation, clot strength, and clot lysis under low-shear conditions, and have been used in a variety of clinical settings and subpopulations, including trauma, cardiac surgery, and obstetrics. Emerging data indicate that these devices are useful for detecting important coagulation defects during major postpartum hemorrhage (especially low plasma fibrinogen concentration [hypofibrinogenemia]) and informing clinical decision-making for blood product use. Data from observational studies suggest that, compared with traditional formulaic approaches to transfusion management, targeted or goal-directed transfusion approaches using data from viscoelastic hemostatic assays are associated with reduced hemorrhage-related morbidity and lower blood product requirement. Viscoelastic hemostatic assays can also be used to identify and treat coagulation defects in patients with inherited or acquired coagulation disorders, such as factor XI deficiency or immune-mediated thrombocytopenia, and to assess hemostatic profiles of patients prescribed anticoagulant medications to mitigate the risk of epidural hematoma after neuraxial anesthesia and postpartum hemorrhage after delivery.

Current and future strategies to monitor and manage coagulation in ECMO patients

Extracorporeal membrane oxygenation (ECMO) can provide life-saving support for critically ill patients suffering severe respiratory and/or cardiac failure. However, thrombosis and bleeding remain common and complex problems to manage. Key causes of thrombosis in ECMO patients include blood contact to pro-thrombotic and non-physiological surfaces, as well as high shearing forces in the pump and membrane oxygenator. On the other hand, adverse effects of anticoagulant, thrombocytopenia, platelet dysfunction, acquired von Willebrand syndrome, and hyperfibrinolysis are all established as causes of bleeding. Finding safe and effective anticoagulants that balance thrombosis and bleeding risk remains challenging. This review highlights commonly used anticoagulants in ECMO, including their mechanism of action, monitoring methods, strengths and limitations. It further elaborates on existing anticoagulant monitoring strategies, indicating their target range, benefits and drawbacks. Finally, it introduces several highly novel approaches to real-time anticoagulation monitoring methods including sound, optical, fluorescent, and electrical measurement as well as their working principles and future directions for research.

Optimal Tests to Minimise Bleeding and Ischaemic Complications in Patients on Extracorporeal Membrane Oxygenation

Patients supported with extracorporeal membrane oxygenation (ECMO) experience a very high frequency of bleeding and ischaemic complications, including stroke and systemic embolism. These patients require systemic anticoagulation, mainly with unfractionated heparin (UFH) to prevent clotting of the circuit and reduce the risk of arterial or venous thrombosis. Monitoring of UFH can be very challenging. While most centres routinely monitor the activated clotting time and activated partial thromboplastin time (aPTT) to assess UFH, measurement of anti-factor Xa (anti-Xa) level best correlates with heparin dose, and appears to be predictive of circuit thrombosis, although aPTT may be a better predictor of bleeding. Although monitoring of prothrombin time, platelet count and fibrinogen is routinely undertaken to assess haemostasis, there is no clear guidance available regarding the optimal test.Additional tests, including antithrombin level and thromboelastography, can be used for risk stratification of patients to try and predict the risks of thrombosis and bleeding. Each has their specific role, strengths and limitations. Increased thrombin generation may have a role in predicting thrombosis. Acquired von Willebrand syndrome is frequent with ECMO, contributing to bleeding risk and can be detected by assessing the von Willebrand factor activity-to-antigen ratio, while the platelet function analyser can be used in urgent situations to detect this, with a high negative predictive value. Tests of platelet aggregation can aid in the prediction of bleeding.To personalise management, a selection of complementary tests to collectively assess heparin-effect, coagulation, platelet function and platelet aggregation is proposed, to optimise clinical outcomes in these high-risk patients.

Viscoelastic Hemostatic Assays: A Primer on Legacy and New Generation Devices

Viscoelastic hemostatic assay (VHAs) are whole blood point-of-care tests that have become an essential method for assaying hemostatic competence in liver transplantation, cardiac surgery, and most recently, trauma surgery involving hemorrhagic shock. It has taken more than three-quarters of a century of research and clinical application for this technology to become mainstream in these three clinical areas. Within the last decade, the cup and pin legacy devices, such as thromboelastography (TEG^® 5000) and rotational thromboelastometry (ROTEM^® delta), have been supplanted not only by cartridge systems (TEG^® 6S and ROTEM^® sigma), but also by more portable point-of-care bedside testing iterations of these legacy devices (e.g., Sonoclot^®, Quantra^®, and ClotPro^®). Here, the legacy and new generation VHAs are compared on the basis of their unique hemostatic parameters that define contributions of coagulation factors, fibrinogen/fibrin, platelets, and clot lysis as related to the lifespan of a clot. In conclusion, we offer a brief discussion on the meteoric adoption of VHAs across the medical and surgical specialties to address COVID-19-associated coagulopathy.

Viscoelastic Hemostatic Assays for Postpartum Hemorrhage

This article discusses the importance and effectiveness of viscoelastic hemostatic assays (VHAs) in assessing hemostatic competence and guiding blood component therapy (BCT) in patients with postpartum hemorrhage (PPH). In recent years, VHAs such as thromboelastography and rotational thromboelastometry have increasingly been used to guide BCT, hemostatic adjunctive therapy and prohemostatic agents in PPH. The three pillars of identifying hemostatic competence include clinical observation, common coagulation tests, and VHAs. VHAs are advantageous because they assess the cumulative contribution of all components of the blood throughout the entire formation of a clot, have fast turnaround times, and are point-of-care tests that can be followed serially. Despite these advantages, VHAs are underused due to poor understanding of correct technique and result interpretation, a paucity of widespread standardization, and a lack of large clinical trials. These VHAs can also be used in cases of uterine atony, preeclampsia, acute fatty liver of pregnancy, amniotic fluid embolism, placental abruption, genital tract trauma, surgical trauma, and inherited and prepartum acquired coagulopathies. There exists an immediate need for a point-of-care test that can equip obstetricians with rapid results on developing coagulopathic states. The use of VHAs in predicting and treating PPH, although in an incipient state, can fulfill this need.

Viscoelastic testing in benign hematologic disorders: Clinical perspectives and future implications of point-of-care testing to assess hemostatic competence

Viscoelastic tests (VETs) have been used routinely for liver transplantation, cardiac surgery, and trauma, but only recently have found clinical utility in benign hematologic disorders. Therefore, guidelines for diagnosis and treatment of these disorders based on viscoelastic variables have been adapted from the existing transplant, cardiothoracic surgery, and trauma resuscitation literature. As a result, diagnostic and therapeutic strategies for benign hematologic disorders utilizing VETs are not uniform. Accordingly, even though there has been a recent increase in the utilization of VET for the diagnosis and treatment of such disorders, the literature is still in its early stages. Analysis of point-of-care viscoelastic tracings from benign hematologic disorders has the potential to allow prompt recognition of disease and to guide patient-specific intervention. Here we present a review describing the application of VETs to benign hematologic disorders.

Heyde Syndrome-Pathophysiology and Perioperative Implications

Gastrointestinal (GI) bleeding in patients with calcific aortic valve stenosis (AVS), termed Heyde syndrome, was first described by Edward C. Heyde. The strong association between valvular replacement and the eradication of clinically significant GI bleeding confirmed an underlying pathophysiologic relationship. The rheologic stress created by AVS increases proteolysis of von Willebrand factor (VWF), resulting in loss of predominantly high-molecular-weight VWF (Hmw VWF). Angiodysplastic vessels present in patients with AVS, coupled with the lack of functioning Hmw VWF, increase the risk for GI bleeds. Aortic valve replacement, both surgical and transcatheter-based, is often a definitive treatment for GI bleeding, leading to recovery of Hmw VWF multimers. Perioperative management of patients involves monitoring their coagulation profiles with relevant laboratory tests and instituting appropriate management. Management can be directed in the following two ways: by improving internal release of VWF or by administration of external therapeutics containing VWF. It is important for perioperative physicians to obtain an understanding of the pathophysiology of this disease process and closely monitor the bleeding pattern so that targeted therapies can be initiated.

Utility of thromboelastography for the diagnosis of von Willebrand disease

Von Willebrand disease (VWD) is an inherited bleeding disorder that is caused by a quantitative or qualitative deficiency of von Willebrand factor (VWF). The National Heart, Lung, and Blood Institute (NHLBI) guidelines for the diagnosis of VWD state that a VWF activity (VWF:RCo) of <30 IU/dL or <50 IU/dL with symptoms of clinical bleeding are consistent with the diagnosis of VWD. However, current gold-standard diagnostic testing takes days to have complete results. Thromboelastography (TEG) is a testing method that provides a graphical trace that represents the viscoelastic changes seen with fibrin polymerization in whole blood, therefore providing information on all phases of the coagulation process. This study describes the TEG characteristics in 160 patients who presented for workup of a bleeding disorder and a subset of those were subsequently diagnosed with VWD. The TEG parameters, K-time (representing the dynamics of clot formation) and the maximal rate of thrombus generation (MRTG), were found to be sensitive in detecting patients with VWF:RCo <30 IU/dL. The TEG, unlike VWF:RCo, can be done in real time, and results are available to the clinician within an hour. This will definitely be beneficial in acute situations such as evaluation of and management of acute bleeding in patients with acquired deficiencies of VWF and may play an important role in the surgical management of patients with VWD.

Thromboelastometry as a diagnostic tool in mild bleeding disorders: A prospective cohort study

BACKGROUND

Major guidelines emphasise the potential of visco-elastic methods to overcome the limitations of conventional laboratory assays in the peri-operative setting. Their sensitivity regarding mild bleeding disorders (MBDs), the most common bleeding disorders in the general population, is however unknown.

OBJECTIVE

The aim of this study was to investigate the sensitivity of thromboelastometry for diagnosis of MBD.

DESIGN

A single-centre prospective cohort study.

SETTING

Haematology outpatient unit of a tertiary general hospital in Central Switzerland.

PATIENTS

All consecutive patients referred over a 32-month period with a suspected bleeding disorder were included and thromboelastometry was conducted using a ROTEM delta (EXTEM, INTEM and FIBTEM). Diagnostic work-up was performed according to current guidelines including the ISTH bleeding assessment tool (ISTH BAT).

MAIN OUTCOME MEASURES

Distribution of clotting time (CT) and maximum clot firmness (MCF) results in relation to the presence of MBD.

RESULTS

Two hundred and seventeen patients were assessed; the median [IQR] age was 39 years [28 to 57]; 151 patients were women (70%). MBD was diagnosed in 97 patients (45%), no MBD was found in 100 patients (46%) and a systemic disorder recognised in 20 patients (9%). Presence of MBD was not associated with a significant difference in thromboelastometry variables (0.2 s in CT EXTEM, 95% CI -2.3 to 2.7; -0.2 mm in MCF EXTEM, 95% CI -1.8 to 1.5; -0.7 s in CT INTEM, 95% CI -12.6 to 11.2; 0.6 mm in MCF INTEM, 95% CI -1.2 to 1.3; 0.8 mm in MCF FIBTEM, 95% CI -1.6 to 1.4) and most results were within the established reference ranges.

CONCLUSION

Our data did not support the use of thromboelastometry as a diagnostic tool in patients with MBD.

Platelets compensate for poor thrombin generation in type 3 von Willebrand disease

In type 3 von Willebrand disease (VWD3), the most severe form with absent von Willebrand factor (VWF), the bleeding phenotype is variable. Platelet contribution to the hemostatic defect in VWD3 calls upon further studies. We investigated the contribution of platelets to in vitro thrombin generation (TG) and platelet procoagulant activity in VWD3. TG was assessed by calibrated automated thrombogram (CAT) in platelet-poor (PPP) and -rich plasma (PRP) from 9 patients before and in 6 patients also 30 min after receiving their regular VWF therapy. Responsiveness of PPP to FVIII and protein S was also investigated. TG data were compared with routine laboratory variables, rotational thromboelastometry (ROTEM) and platelet expression of P-selectin and phosphatidylserine in flow cytometry. Compared with healthy controls, TG was markedly decreased in VWD3 PPP (peak thrombin was 16% of normal median), but not in PRP (77% of normal median) (p = 0.002). Six out of nine patients (67%) were high responders in their platelet P-selectin, and 5/9 (56%) in phosphatidylserine expression. Replacement therapy improved TG in PPP, while in PRP TG only modestly increased or was unaffected. In PPP, FVIII levels associated with TG and in vitro FVIII-supplemented TG inclined up to threefold. Conversely, a FVIII inhibitory antibody reduced plasma TG in all, but especially in patients with remnant FVIII levels. Inhibition of protein S improved plasma TG, particularly at low FVIII levels. ROTEM failed to detect VWD3.In VWD3, TG is reduced in PPP and regulated by FVIII and protein S, but TG is close to normal in PRP. VWD3 platelets seem to compensate for the FVIII-associated reduction in TG by their exposure of P-selectin and phosphatidylserine.

Closing the gap - detection of clinically relevant von Willebrand disease in emergency settings through an improved algorithm based on rotational Thromboelastometry

Background

Hemorrhage and blood loss are still among the main causes of preventable death. Global hemostatic assays are useful point-of-care test (POCT) devices to rapidly detect cumulative effects of plasma factors and platelets on coagulation. Thromboelastography (TEG) and Thromboelastometry (ROTEM) are established methods in many anesthesiological departments for guided hemostatic treatment. However, von Willebrand disease remains undetected by standard ROTEM, especially during emergency care, despite being the most prevalent congenital hemostatic disorder.

Methods

In our monocentric cohort pilot study we focused on hemostatic challenges associated with von Willebrand disease. Twenty-seven patients with suspected von Willebrand disease were included. We modified the routine ROTEM assay by adding a preincubation with ristocetin and commercially available plasma-derived von Willebrand factor to identify clinically relevant von Willebrand disease (VWD).

Results

Addition of von Willebrand factor to the ristocetin assay of a VWD type 3 patient restored the reaction of the whole blood probe to match the response of a healthy person. Our modified ROTEM assay with ristocetin (Ricotem) showed that all high responders (n = 7) had VWD. In the low responder group (n = 16) – 10 of 16 had VWD and in the normal responder group (n = 5), 2 of 5 had mild type 1 VWD.

Conclusions

This new modification of the standard ROTEM assay enables the detection of otherwise unnoticed critical von Willebrand disease based on alterations in clot formation and might serve as a novel approach to reliably assess severe VWD patients by platelet-mediated blood clotting in an emergency setting. We recommend incorporating this new VWD-focused screening tool into the current ROTEM-based management algorithm of acute microvascular bleeding.

Electronic supplementary material

The online version of this article (10.1186/s12871-018-0672-8) contains supplementary material, which is available to authorized users.

An introduction to point-of-care testing in extracorporeal circulation and LVADs

There is a delicate balance between bleeding and clotting in patients on circuits such as ventricular assist devices or extracorporeal membrane oxygenation. Traditional coagulation tests, prothrombin time, activated partial thromboplastin time, and anti-factor Xa levels, are used to monitor patients on these devices. However, turnaround times and inability to assess global hemostasis, including platelets and fibrinogen have contributed to a recognition that faster, accurate, and more informative coagulation tests are needed. Activated clotting time is used to monitor heparin in patients on circuits and has the advantages of being a near-patient point-of-care test. However, its utility is limited to heparin monitoring. Viscoelastic tests (thromboelastometry and thromboelastography) are global, whole-blood coagulation tests, and whole-blood platelet aggregometry evaluates platelet function. Ideally, these tests can ensure that patients are within the therapeutic range of their antithrombotic medications, identify patients at risk for hemorrhagic or thrombotic complications, and guide management of acute bleeding complications. This ideal is currently hampered by a lack of studies that delineate clear ranges that are clinically relevant. Future research is needed to better understand the optimal use of point-of-care coagulation testing in patients on extracorporeal circuits and ventricular assist devices.

Viscoelastic Monitoring to Guide Hemostatic Resuscitation in Liver Transplantation Surgery

Coagulopathic bleeding must be anticipated during liver transplantation (LT) surgery. Patients with end-stage liver disease (ESLD) often present with disease-related hematologic disturbances, including the loss of hepatic procoagulant and anticoagulant clotting factors and thrombocytopenia. Transplantation surgery itself presents additional hemostatic changes, including hyperfibrinolysis. Viscoelastic monitoring (VEM) is often used to provide targeted, personalized hemostatic therapies for complex bleeding states including cardiac surgery and major trauma. The use in these coagulopathic conditions led to its application to LT, although the mechanisms of coagulopathy in these patients are quite different. While VEM is often used during transplant surgeries in Europe and North America, evidence supporting its use is limited to a few small clinical studies. The theoretical and clinical applications of the standard and specialized VEM assays are discussed in the setting of LT and ESLD.

Whole blood ristocetin-activated platelet impedance aggregometry (Multiplate) for the rapid detection of Von Willebrand disease

Von Willebrand disease (VWD) is the most common bleeding disorder, but no bedside tests specific for Von Willebrand factor are available. The objective of this study was to evaluate the diagnostic accuracy of whole blood ristocetin-induced platelet aggregometry (WB-RIPA) in VWD. WB-RIPA was performed in VWD patients (n=100) and healthy controls (n=17) using the Multiplate® platelet impedance aggregometry platform. The diagnostic properties of the test were described as sensitivity/specificity, positive and negative predictive value, and ROC area under the curve (AUC). Patients with VWD had impaired platelet aggregation by WB-RIPA. At a cut-off of 98 U, the test sensitivity and specificity of WB-RIPA for VWD was 0.95 and 0.53. A cut-off of 60 U provided a specificity of 1.00 with reduced sensitivity of 0.76. All patients with type 3 VWD and >90 % of patients with type 2 VWD were accurately distinguished from the controls. Incorrect classifications were attributable to patients with type 1 VWD, showing partly overlapping WB-RIPA results with healthy controls. Remarkably, these patients had lower bleeding scores and higher VWF activity than other type 1 VWD patients. Overall, WB-RIPA discriminated VWD patients from healthy controls accurately with a ROC AUC of 0.94. These results show that WB-RIPA is a promising diagnostic test for VWD, especially when timely results are required. Depending on the chosen test threshold, WB-RIPA could be clinically used as a rule out test, or to suggest patients in whom further testing for VWD is warranted.