Minimal interference of concizumab with standard clinical coagulation laboratory assays - An in vitro study.

INTRODUCTION: Non-factor replacement therapies are emerging as prophylactic treatment options in haemophilia A or B (HA/HB) with and without inhibitors. Concizumab is an anti-tissue factor pathway inhibitor (TFPI) monoclonal antibody preventing factor (F)Xa inhibition and enhancing thrombin generation. Based on experience with other non-factor therapies and extended half-life products, there is a focus on potential interference with common clinical coagulation assays used to monitor patients treated with concizumab. AIM: To evaluate the impact of concizumab on standard clinical coagulation assays. METHODS: Plasma samples (normal, HA/HB with/without inhibitors) in the presence/absence of added concizumab (250-16,000 ng/mL) were analysed in clinical assays including activated partial thromboplastin time (aPTT), prothrombin time (PT), FVIII and FIX one-stage clot and chromogenic substrate assay, assays for detecting FVIII or FIX inhibitors and other assays for coagulation factors. RESULTS: Concizumab did not impact PT assays, but resulted in a small shortening of aPTT (up to 5 s in haemophilia plasma and 0.4 s in normal plasma). Concizumab had no, or only a minor impact on FVIII and FIX activity assays or Bethesda inhibitor assays. FXI and FXII activity in normal plasma, as measured by single factor aPTT-based assay, was significantly increased in the presence of concizumab (+11% each). This was also the case for FVII and FX measured by PT-based assays using plasma with 25% of FVII or FX (+64% and +22%, respectively). CONCLUSION: The presence of concizumab did not, or only slightly, influence the outcome of standard clinical coagulation assays relevant for HA and HB.

A nonneutralizing antibody as cause of prothrombin deficiency in a patient with follicular lymphoma.

Acquired inhibitors of blood coagulation are rare but of clinical importance. Prothrombin is a vitamin K-dependent protein, and acquired antibodies toward prothrombin are often associated with the presence of lupus anticoagulant. We describe a previously healthy 70-year-old man presenting with both hemorrhage and thrombosis as well as a prolonged prothrombin time. At arrival at the hospital, he was diagnosed with deep venous thrombosis, and an enlarged lymph node in the left groin was noted (revealed as follicular lymphoma grade 1 by biopsy). Prothrombin activity and antibody titer were followed for 5 months with 15 sampling time points to monitor the treatment outcome of the patient. Diagnostic work-up identified prothrombin deficiency as cause of bleeding. A nonneutralizing calcium-dependent antiprothrombin antibody was found, suspected to increase the clearance of prothrombin, which has previously only occasionally been reported. Lupus anticoagulant was ruled out and thrombosis was judged to be caused by a combination of malignant disease and stagnant venous flow following enlarged lymph nodes in the groin. This report illustrates how investigation of prolonged global coagulation tests, triggered the diagnosis of a rare but critical condition, immune-mediated prothrombin deficiency. The diagnosis is challenging and involves proper differential diagnosis.

Infrastructural considerations of implementing gene therapy for hemophilia in the Nordic context.

Background: Despite improvements in hemophilia care, challenges remain, including treatment burden and impaired quality of life. Gene therapy may overcome these. However, its introduction presents a challenge. Objectives: To outline a function-based gene therapy working model describing critical milestones associated with gene therapy handling, administration, and follow-up to facilitate and implement an effective infrastructure for gene therapy introduction. Design: Literature review and consensus discussion among Hemophilia Comprehensive Care centers (HCCCs) in the Nordic region. Methods: Representatives from six HCCCs sought to pinpoint milestones and key stakeholders for site readiness at the pre-, peri-, and post-infusion stages, including authority and genetically modified organism (GMO) product requirements, awareness, medical eligibility, logistics and product handling for infusion, laboratory monitoring, and follow-up. Results: A gene therapy transit map was developed with key stakeholders identified. The approach to prepare the vector will differ between the Nordic centers, but the contracted pharmacy unit will be a key stakeholder. Therefore, a pharmacy checklist for the implementation of gene therapy was developed. For the future, Advanced Therapy Medicinal Product centers will also be implemented. Patients' expectations, commitments, and concerns need to be addressed repeatedly and education of patients and the expanded health-care professionals team will be the key to successful and optimal clinical management. Eligibility testing according to the product's summary of product characteristics and frequent follow-up and monitoring post-infusion according to the World Federation of Hemophilia chart will be crucial. Conclusion: The approach to deliver gene therapy in the Nordic region will differ partly between the hemophilia centers, but the defined road map with checklists for the implementation of this advanced therapy will be applicable to all. The map may also serve as a platform for the use of future GMO product options both within and outside the area of hemophilia.

Implementing gene therapy for hemophilia in the Nordic context Why was this study done? • Despite improvements in hemophilia care, challenges remain including treatment burden and impaired quality of life. • Gene therapy may overcome these challenges. • The introduction of gene therapy presents a challenge in many ways. What did the researchers do? • We, as representatives from six Hemophilia Comprehensive Care Centers in the Nordic region, sought to pinpoint milestones and key stakeholders for site readiness at the pre-, peri- and post-infusion stages, including authority and genetically modified organism (GMO) product requirements, awareness, medical eligibility, logistics and product handling for infusion, laboratory monitoring, plus follow-up. What did the researchers find? • We developed a gene therapy transit map and identified key stakeholders. • The approach to prepare the vector will differ between the Nordic centers, but the pharmacy unit will be a key stakeholder. We therefore developed a pharmacy checklist for the implementation of gene therapy. • For the future, Advanced Therapy Medicinal Product centers will be implemented. • Patients' expectations, commitments and concerns need to be addressed repeatedly. • Education of patients and the expanded health care professionals team will be the key to successful and optimal clinical management. • Eligibility testing according to the product's summary of product characteristics and close follow-up and monitoring post-infusion according to the World Federation of Hemophilia chart will be crucial. • Access to both chromogenic and one-stage factor activity assay results from a specialized coagulation laboratory with a short turn-around time is important. What do the findings mean? • The approach to delivering gene therapy in the Nordic region will differ partly between the hemophilia centers, but the defined road map with checklists for the implementation will be applicable to all. • The map may also serve as a platform for the use of future GMO product options both within and outside the area of hemophilia.

[Analysis with viscoelastic hemostatic assays - a guide]. / En guide till koagulationsanalys med viskoelastiska instrument.

Viscoelastic hemostasis analyses (VHA) are a complement in the evaluation of hemostasis in patients with major bleeding. The analysis measures viscoelastic changes in whole blood and the results give an overview of several components of hemostasis. VHA can be used to optimize fibrinogen levels, platelet and plasma substitution. The main clinical evidence supporting this strategy is in trauma, obstetric bleeding, heart and liver surgery, where algorithms based on VHA results facilitate individualized therapy. VHA measurement is of limited value to exclude treatment with anticoagulants and platelet inhibitors. Quality control aspects are also more cumbersome since whole blood with limited sustainability is used. Newer, more automated versions of the instruments have increased the reproducibility. The main advantage of VHA is the fast turn-around time and their role in guiding treatment in an emergency situation with bleeding.

[Factor XIII deficiency - not only a congenital bleeding disorder]. / Koagulationsfaktor XIII ­ inte bara ett kongenitalt blödningsproblem.

Factor XIII (FXIII) cross-links fibrin monomers to strengthen clots. The congenital severe autosomal type of FXIII deficiency with <5 percent of normal FXIII activity is an extremely rare bleeding disorder with <10 cases in Sweden. It often debuts at birth with prolonged umbilical cord bleedings and an increased risk for bleeding throughout life. Patients with severe congenital FXIII deficit have an established FXIII concentrate treatment, both for prophylaxis and at bleeding episodes. Acquired autoantibodies against FXIII are also rare, with high bleeding risks. Quantitative FXIII analyses are only available in few laboratories in Sweden. Sometimes more complex antigen/antibody/gene mutation tests are needed for diagnosis, but these are not available in Sweden. Other acquired FXIII deficiencies can occur in patients with several diseases and during surgery/trauma. Their treatment and diagnostic logistics are less defined. Recent European guidelines on perioperative bleeding have suggested FXIII concentrate treatment.

Methods for anti-factor VIII antibody levels in haemophilia A patients - validation of a multiplex immunoassay and comparability with assays measuring non-neutralising and neutralising antibodies (inhibitors).

INTRODUCTION: The development of neutralising (inhibitors) and non-neutralising antibodies (NNAs) is a complication to factor replacement therapy in haemophilia. The diagnostic methods available lack standardisation, have high inter-laboratory variation, and false-negative as well as false-positive results may affect treatment. Both functional inhibitors and NNAs may be detected with higher reproducibility, sensitivity and specificity using the immunological Luminex xMAP-based fluorescence-immunoassay (xFLI). AIM: Validation of our xFLI and comparability with enzyme-linked immunosorbent assay (ELISA) and chromogenic Nijmegen-Bethesda assay (CBA) for anti-FVIII antibodies in haemophilia A (HA) patients. METHODS: The xFLI method was developed with full-length and B-domain deleted factor coupled to magnetic beads, optimised and validated for performance characteristics. Comparability with ELISA and CBA was evaluated in HA patient samples (n = 112), serial samples in six inhibitor patients and reference interval and decision-limits in healthy donors (n = 44). RESULTS: The intra- and inter-assay precision (CV%) for the xFLI method was below 6% and detection limit (LLOQ) .084 ng/mL (NovoEight). All ELISA-positive samples were positive with either Advate or NovoEight. Additionally, 10.7%-14.3% were xFLI-positive and ELISA-negative. All but one CBA-positive sample was above 3SD with xFLI; one was between 2 and 3SD. 29.1% were xFLI-positive and CBA negative. The overall concordance between xFLI and ELISA was 82.1% and xFLI and CBA 77.9%. CONCLUSION: The anti-FVIII antibody xFLI method is adaptable to clinical practice and more sensitive and reproducible than ELISA and CBA. Actual NNA titers are determined to both full-length and B-domain deleted FVIII. The xFLI is thus valuable for confirmation of all anti-FVIII antibodies.

A prospective, controlled study on the utility of rotational thromboelastometry in surgery for acute type A aortic dissection.

To evaluate the hemostatic system with ROTEM in patients undergoing surgery for acute type aortic dissection (ATAAD) using elective aortic procedures as controls. This was a prospective, controlled, observational study. The study was performed at a tertiary referral center and university hospital. Twenty-three patients with ATAAD were compared to 20 control patients undergoing elective surgery of the ascending aorta or the aortic root. ROTEM (INTEM, EXTEM, HEPTEM and FIBTEM) was tested at 6 points in time before, during and after surgery for ATAAD or elective aortic surgery. The ATAAD group had an activated coagulation coming into the surgical theatre. The two groups showed activation of both major coagulation pathways during surgery, but the ATAAD group consistently had larger deficiencies. Reversal of the coagulopathy was successful, although none of the groups reached elective baseline until postoperative day 1. ROTEM did not detect low levels of clotting factors at heparin reversal nor low levels of platelets. This study demonstrated that ATAAD is associated with a coagulopathic state. Surgery causes additional damage to the hemostatic system in ATAAD patients as well as in patients undergoing elective surgery of the ascending aorta or the aortic root. ROTEM does not adequately catch the full coagulopathy in ATAAD. A transfusion protocol in ATAAD should be specifically created to target this complex coagulopathic state and ROTEM does not negate the need for routine laboratory tests.

Factor IX antibodies and tolerance in hemophilia B in the Nordic countries - The impact of F9 variants and complications.

INTRODUCTION: The development of inhibitory antibodies (inhibitors) in persons with hemophilia B (PwHB) causes significant morbidity. Data on the impact of the F9 variant and immune tolerance induction (ITI) outcome are limited. The aim of this study was to investigate the presence of neutralizing and non-neutralizing antibodies (NNA) in severe hemophilia B (HB) and to evaluate ITI outcome and complications in relation to the pathogenic F9 variant. MATERIALS AND METHODS: Persons with severe HB in the Nordic countries were enrolled and information on F9 variants, inhibitors, ITI and complications were collected. Analyses of anti-FIX antibodies with a fluorescence-immunoassay (xFLI) and an ELISA method were conducted. RESULTS: Seventy-nine PwHB were enrolled. Null variants were seen in 33 (42 %) PwHB and 12 (15 %) had a current or former inhibitor. Eleven (92 %) of the inhibitor patients had experienced allergic manifestations and three (25 %) nephrotic syndrome. Of 10 PwHB with at least one ITI attempt, eight (80 %) were considered tolerant at enrolment. Immunosuppression was included in seven of eight successful or partially successful attempts. Five PwHB had at least one ITI failure before a successful or partially successful ITI. No NNA could be identified. CONCLUSION: A high proportion of severe F9 gene defects among persons with severe HB in the Nordic countries may explain the observed relatively high prevalence of inhibitors. ITI success was independent of the F9 variant and attained despite allergic manifestations and previous ITI failures. Inclusion of immunosuppression tentatively enhances the chances of ITI success. No NNA were observed.

[Routine screening with APTT is not indicated before surgery]. / Rutinmässig screening med APTT är inte indicerad före operation.

Activated partial thromboplastin time (APTT) is widely practiced in preoperative screening. The value of using this test to predict the risk of perioperative bleeding is not well documented in Sweden. In this article, a literature review is performed to determine whether unselected APTT testing can predict abnormal perioperative bleeding. The current literature does not support coagulation screening with APTT in routine perioperative bleeding assessment, as preoperative screening with APTT has a low sensitivity for detection of clinically significant bleeding disorder. While a comprehensive bleeding history is crucial, the APTT test should only be performed on patients with a history of increased bleeding tendency. The conclusion of this literature review is that patients with a negative bleeding history do not require routine screening with APTT prior to surgery, which, if implemented, would lead to a more cost-effective perioperative routine.

Evaluation of the Atellica COAG 360 coagulation analyzer in a specialized coagulation laboratory.

BACKGROUND: Diagnosis of bleeding disorders includes correct analysis of coagulation factors VIII, IX, XI, XII, XIII, II, V, VII, and X and von Willebrand antigen and activity. The aim of this study was to evaluate the analytical performance of the Atellica COAG 360 analyzer in a specialized coagulation laboratory with focus on specific coagulation parameters involved in the diagnosis of bleeding disorders. METHODS: Verification included assessment of precision, reference interval, and method comparison according to local guidelines. For FVIII (Chromogenix) and FIX (Rossix), extended verifications were performed with additional assessment of linearity, detection limit, and comparability to BCS-XP. RESULTS: The precision was below 5% (normal levels) and below 10% (abnormal levels) and either improved or similar when compared to expected target values from a BCS-XP. The locally established reference range agreed well (≥80% of measured values within manufacturer's assigned ranges) for most of the methods. The lower limit of quantification was calculated to below 0.01 IU/ml for FVIII chromogenic (Chromogenix) and FIX chromogenic (Rossix), both with acceptable linearity. Bland-Altman analyses revealed generally good agreement between Atellica COAG 360 and BCS-XP in the determination of coagulation parameters, and differences between the two instruments did not result in any diagnostic change. CONCLUSIONS: The results of the evaluation show that the Atellica COAG 360 analyzer performs as expected to target values and equivalent to BCS-XP for the diagnosis of bleeding disorders in a specialized coagulation laboratory providing service to a hemophilia treatment center (HTC).

Antiphospholipid antibodies in patients with myocardial infarction with and without obstructive coronary arteries.

BACKGROUND: Recent studies demonstrate that prothrombotic antiphospholipid antibodies (aPL) are overrepresented in patients with myocardial infarction (MI) due to coronary artery disease (MICAD). However, it is not known whether aPL differ between the two subsets of MI: MICAD and MI with nonobstructive coronary arteries (MINOCA). OBJECTIVES: To determine whether aPL are associated with MINOCA or MICAD, or with hypercoagulability as assessed by activated protein C-protein C inhibitor (APC-PCI) complex. METHODS: Well-characterized patients with MINOCA (n = 98), age- and gender-matched patients with MICAD (n = 99), and healthy controls (n = 100) were included in a cross-sectional case-control study. Autoantibodies (IgA/G/M) targeting cardiolipin and ß2 glycoprotein-I and specific nuclear antigens were analyzed by multiplexed bead technology. The concentration of APC-PCI was determined as a measure of hypercoagulability by an immunofluorometric sandwich assay. RESULTS: Both prevalence and titers of aPL of the IgG isotype (anti-cardiolipin and/or anti-ß2 glycoprotein-I) were higher in patients with MINOCA and MICAD than in controls. aPL IgG positivity was twice as frequent among patients with MICAD than MINOCA (11% vs. 6%, nonsignificant). We observed no group differences regarding aPL IgA/M or antibodies targeting specific nuclear antigens. Levels of APC-PCI were elevated in aPL IgG-positive compared to aPL IgG-negative MICAD patients. CONCLUSIONS: aPL IgG, but not IgA/M, are enriched particularly in patients with MICAD but also in patients with MINOCA, as compared to controls. Interestingly, signs of hypercoagulability-measured by increased levels of the APC-PCI complex-were present in aPL IgG-positive MICAD patients, indicating an association with functional disturbances of the coagulation system.

Validation of factor VIII activity for monitoring standard and extended half-life products and correlation to thrombin generation assays.

INTRODUCTION: Monitoring replacement therapy with standard and extended half-life (EHL) products is challenging, since one-stage assay (OSA) and chromogenic substrate assay (CSA) results may differ significantly. Recent recommendations include local validation of each new product with recovery within 20-30%, depending on activity level. AIM: To validate factor VIII (FVIII) activity for monitoring products in clinical use on Atellica Coag and to correlate it with thrombin generation. METHODS: Plasma samples spiked with Advate® , Elocta® , Adynovi® , Nuwiq® , NovoEight® and Afstyla® (0.05, 0.20, 0.50 and 0.80 IU/ml) were analysed using Atellica Coag 360 with CSA-1 (Coatest SP) and CSA-2 (FVIII chromogenic), and OSA (Actin FS). Thrombin generation was performed using two thrombin generation assays (TGA-1 (Thrombinoscope) and TGA-2 (Technothrombin). RESULTS: All products at levels above 0.05 IU/ml, except Adynovi, showed acceptable recovery using CSA-1, whereas measurements using CSA-2 gave more results outside the target level. All products, except Afstyla, showed acceptable recovery using OSA. Correlation between CSA-1 and OSA was excellent (r2 =1.0) with biases of 6-3​2%, depending on FVIII product. A clear dose-response was seen for all thrombin generation parameters and products using both methods, except at low levels for lag time using TGA-1. With CSA-1 as an independent variable, the correlations to thrombin peak (measured with TGA-2) were good (r2  = .8-.9). CONCLUSION: Our data revealed good correlation and acceptable bias between CSA and OSA using our sets of reagents, methods and analyser in spiked samples. Thrombin generation gave good correlation to CSA-1 factor activity and is a possible complement to factor activity assays.

Monitoring standard and extended half-life products in hemophilia: Assay discrepancies for factor VIII and IX in pre- and postinfusion samples.

BACKGROUND: Monitoring hemophilia treatment with extended half-life products is challenging for coagulation laboratories since factor assays may show substantial differences between results obtained with the one-stage assay (OSA) and the chromogenic substrate assay (CSA). OBJECTIVES: The aim of this study was to evaluate and compare different factor assays and global coagulation methods. METHODS: Factor VIII (FVIII) and IX (FIX) activities and global assay parameters were analyzed in pre- and postinfusion samples (5 patients 2 samples/product/method). RESULTS: Samples containing FVIII products (NovoEight, Elocta, and Nuwiq) gave higher levels when measured with CSA compared to OSA. The correlation was excellent (r 2 ≥ .97) while biases of 42%-72% of mean (CSA-OSA) were obtained. With FVIII (OSA) as independent variable, the correlations to kaolin clot time (CT) and thrombin generation assay (TGA) peak were modest (r2  = .71-.72 and .64-.65, respectively), except for Nuwiq for which there was a poor correlation to TGA peak (r 2 = .08). Samples containing Alprolix, a FIX product, gave a smaller difference between activity levels (CSA-OSA), and the correlation was excellent (r 2 = .96). With FIX (CSA) as independent variable for both Alprolix and Refixia, the correlations to Innovin CT and TGA peaks were weak (r 2 = .33-.45 and .44-.76, respectively). CONCLUSIONS: Our data show that factor activity assays differ between methods used and agents. These discrepancies indicate the value of having more than one type of assay available in the coagulation laboratory when monitoring hemophilia treatment with extended half-life products. Global assays gave complementary information indicated by the modest correlations to factor activities.

Unveiling the complex effects of direct oral anticoagulants on dilute Russell's viper venom time assays.

INTRODUCTION: Dilute Russell viper venom time (dRVVT) assays can be affected by direct oral anticoagulants (DOACs), which may cause false-positive results. However, there are conflicting results indicating significant differences between different reagents and DOACs. OBJECTIVES: To evaluate the effect of DOACs on dRVVT assays. MATERIAL AND METHODS: Samples were prepared by adding DOAC (dabigatran, rivaroxaban, apixaban, or edoxaban) to pooled normal plasma in the concentration range 0 to 800 µg/L. Six integrated dRVVT reagents were used, all composed of a screen assay (low phospholipid content) and a confirm assay (high phospholipid content). The screen/confirm dRVVT results were expressed as normalized ratios. To further evaluate the observed differences between tests and DOACs, addition of synthetic phospholipids was used. RESULTS: The dRVVT ratios increased dose dependently for all DOACs, with four of the six tests and the DOAC rivaroxaban having the greatest effect. With one test, the ratios were almost unaffected with increasing DOAC concentration, whereas another test revealed a negative dose dependency for all DOACs. Variable DOAC effects can be explained by different effects on dRVVT screen and confirm clotting time. Adding synthetic phospholipids to samples containing rivaroxaban resulted in greatly reduced screen clotting times and thereby lower calculated dRVVT ratios. CONCLUSIONS: There is a great variability in the dRVVT test result with different DOACs. The dRVVT ratios are unaffected for some reagents and this can be explained by an equal dose-dependent effect on both screen and confirm assays. The phospholipid type and content of the different reagents may contribute to the observed differences.

Clinical utility and impact of the use of the chromogenic vs one-stage factor activity assays in haemophilia A and B.

Treatment of haemophilia A/B patients comprises factor VIII (FVIII) or factor IX (FIX) concentrate replacement therapy, respectively. FVIII and FIX activity levels can be measured in clinical laboratories using one-stage activated partial thromboplastin time (aPTT)-based clotting or two-stage chromogenic factor activity assays. We discuss strengths and limitations of these assays, providing examples of clinical scenarios to highlight some of the challenges associated with their current use for diagnostic and monitoring purposes. Substantial inter-laboratory variability has been reported for one-stage assays when measuring the activity of factor replacement products due to the wide range of currently available aPTT reagents, calibration standards, factor-deficient plasmas, assay conditions and instruments. Chromogenic activity assays may avoid some limitations associated with one-stage assays, but their regulatory status, perceived higher cost, and lack of laboratory expertise may influence their use. Haemophilia management guidelines recommend the differential application of one or both assays for initial diagnosis and disease severity characterisation, post-infusion monitoring and replacement factor potency labelling. Efficient communication between clinical and laboratory staff is crucial to ensure application of the most appropriate assay to each clinical situation, correct interpretation of assay results and, ultimately, accurate diagnosis and optimal and safe treatment of haemophilia A or B patients.

von Willebrand factor alloantibodies in type 3 von Willebrand disease.

: The development of neutralizing antibodies is a rare complication of von Willebrand disease treatment. In major surgical procedures for severe forms of the disease, the recognition of ineffective therapy and alternative treatment protocols are lifesaving. We report the case of a 6-year-old girl with type 3 von Willebrand disease in whom inhibitors were sought due to ineffective haemostasis together with lower than expected von Willebrand factor (VWF) recoveries after a surgical procedure. Replacement therapy first with recombinant factor VIIa and then with high doses of recombinant factor VIII in continuous infusion successfully stopped the bleeding. A high level of anti-VWF antibodies was determined by the immunological method. A frameshift mutation associated with premature termination codon (c.2435delC, p.Pro812ArgfsTer31) was determined in our patient. Although the reports on association of this mutation with inhibitor risk are inconsistent, it represents an evidence-based diagnostic and management practice in recognition of high-risk VWF genotype.

The role of von Willebrand factor in acute type A aortic dissection and aortic surgery.

INTRODUCTION: Massive bleeding is a serious complication associated with impaired survival after surgery for acute type A aortic dissection (ATAAD). There are no previous reports evaluating the effect of ATAAD and associated surgery on von Willebrand factor (VWF). The aim of the present study was to analyze VWF activity (VWF:GPIbM) and thus the potential of Factor (F) VIII/VWF concentrate as a treatment for refractory bleeding in surgery for acute type A aortic dissection. MATERIAL AND METHODS: We prospectively compared serial measurements of VWF:GPIbM in 25 patients with ATAAD to 20 control patients undergoing elective surgery of the ascending aorta or the aortic root. In 10 of the ATAAD patients, high molecular weight multimer distribution was measured. RESULTS: Preoperatively, ATAAD patients demonstrated significantly higher VWF:GPIbM (1.58 (1.40-2.05) kIU/L vs 1.25 (1.02-1.42) kIU/L, p = 0.003). In the ATAAD group, VWF:GPIbM significantly decreased to 1.24 (0.98-1.44) kIU/L at lowest core temperature (T0 vs T1 p < 0.001), but remained unchanged in the elective group (1.25 (1.04-1.43) kIU/L, T0 vs T1 p < 0.625). Neither aortic dissection nor hypothermia caused any changes to the proportion of high molecular weight multimers when compared to control patients. Both groups demonstrated supernormal VWF:GPIbM on the first and fifth day after surgery. CONCLUSIONS: This report showed that patients with acute aortic dissection had increased levels of VWF:GPIbM before surgery that decreased slightly during surgery. Our study could not provide evidence that would encourage administration of FVIII/VWF concentrate for major bleeding in patients undergoing surgery for ATAAD as well as elective aortic procedures.

The Coagulopathy of Acute Type A Aortic Dissection: A Prospective, Observational Study.

OBJECTIVE: To evaluate the hemostatic system in patients undergoing surgery for acute type A aortic dissection (ATAAD) compared with those undergoing elective aortic procedures. DESIGN: This was a prospective, observational study. SETTING: The study was performed at a single university hospital. PARTICIPANTS: Twenty-five patients with ATAAD were compared with 20 control patients undergoing elective surgery of the ascending aorta or the aortic root. INTERVENTIONS: No interventions were performed. MEASUREMENTS AND MAIN RESULTS: Platelet count and levels of fibrinogen, D-dimer, prothrombin time/international normalized ratio, activated partial thromboplastin time, and antithrombin were analyzed perioperatively and compared between the 2 groups. Patients with ATAAD had lower preoperative levels of platelets (188 [156-217] × 109/L v 221 [196-240] × 109/L; p = 0.018), fibrinogen (1.9 [1.6-2.4] g/L v 2.8 [2.2-3.0] g/L; p = 0.003), and antithrombin (0.81 [0.73-0.94] kIU/L v 0.96 [0.92-1.00] kIU/L; p = 0.003) and significantly higher levels of D-dimer (2.9 [1.7-9.7] mg/L v 0.1 [0.1-0.2] mg/L; p < 0.001) and prothrombin time/international normalized ratio (1.15 [1.1-1.2] v 1.0 [0.93-1.0]; p = 0.001). Surgery caused significant changes of the coagulation system in both groups. Intraoperative bleeding volumes were larger in the ATAAD group (2,407 [1,804-3,209] mL v 1,212 [917-1,920] mL; p < 0.001), and patients undergoing ATAAD surgery received significantly more transfusions of red blood cells (2.5 [0.25-4.75] U v 0 [0-2.75] U; p = 0.022), platelets (4 [3.25-6] U v 2 [2-4] U; p = 0.002), and plasma (2 [0-4] U v 0 [0-0] U; p = 0.004) compared with the elective group. CONCLUSIONS: This study demonstrates that ATAAD is associated with a coagulopathic state. Surgery causes additional damage to the hemostatic system in ATAAD patients, but also in patients undergoing elective surgery of the ascending aorta or the aortic root.

Evaluation of a standardized protocol for thrombin generation using the calibrated automated thrombogram: A Nordic study.

INTRODUCTION: The thrombin generation assay-calibrated automated thrombogram (TGA-CAT) method is used to measure the overall coagulation capacity in plasma. However, the method is still considered to be a research tool, mainly because of its' lack of standardization. AIM: Our study aimed to further raise the standardization level for the TGA-CAT method by evaluating a detailed standardization protocol and three reference plasmas' (RP)s ability to normalize results. METHODS: Six Nordic centres participated in the study, and with input from all centres a detailed laboratory standardization protocol based on the TGA-CAT manual of the manufacturer was established. Three types of plasma, hypo-,normal and hypercoagulable plasma were assessed. Three commercial lyophilized RPs were used for normalization of data. All samples were aliquoted at the Malmö centre and sent frozen at -20˚C to participating centres. RESULTS: Before normalization, all results under all testing conditions showed inter-laboratory coefficient of variability of 10% or lower except for endogenous thrombin potential (12%) and peak (14%) in hypo-plasma with 1 pmol/L tissue factor as starting agent. Successful normalization, improving variability in results, was obtained with two of the three evaluated RPs (HemosIL RP and Affinity RP). CONCLUSION: With our standardization concept, we were able to produce TGA-CAT results as robust as standard coagulation assays used in the routine laboratories. Normalization with HemosIL RP may be considered in populations with low or unknown coagulability, while when analysing plasma samples from populations where hypercoagulability is known or suspected, normalization with Affinity RP may be preferred.