Optimal monitoring of bypass therapy in hemophilia A patients with inhibitors by the use of clot waveform analysis

Clot Waveform Analysis for Monitoring Hemostasis

Clot waveform analysis (CWA) is a recently developed global coagulation assessment, based on the continuous observation of changes in light transmittance, absorbance, or light scattering that occurs as fibrin formed in a plasma sample during routine clotting tests such as activated partial thromboplastin time (aPTT) and prothrombin time (PT). CWA can utilize qualitative waveform patterns as well as sensitive quantitative parameters and can be used as a simple method to assess global hemostasis, and can be applied to various challenging clinical situations. Although not all coagulation analyzers currently in use are able to provide CWA, the number of analyzers available to do so is increasing, as the usefulness of this process has become more widely recognized. CWA can be based on the coagulation mechanism of aPTT, an intrinsic trigger, and this has been reported in many studies, including diagnosis and treatment of patients with hemophilia, disseminated intravascular coagulation, and monitoring of anticoagulants and thrombosis. CWA using trace amounts of tissue factors also has the potential to expand the applications of this technology. Recently, there have been reports of the combined evaluation of fibrinolytic dynamics. Among the existing global coagulation assays, CWA may prove to be the easiest to standardize in clinical practice. However, more extensive testing using standardized methods in various clinical settings is needed to determine the true role of CWA in the evaluation of hemostasis and thrombosis in the future.

Hemophilia A: Emicizumab monitoring and impact on coagulation testing

Hemophilia A is an X-linked recessive bleeding disorder characterized by absent or ineffective coagulation factor VIII, a condition that could result in a severe and potentially life-threatening bleed. Although the current standard of care involves prophylactic replacement therapy of factor VIII, the development of neutralizing anti-factor VIII alloantibody inhibitors often complicates such therapeutic treatment. Emicizumab (Hemlibra®), a novel recombinant therapeutic agent for patients with hemophilia A, is a humanized asymmetric bispecific IgG4 monoclonal antibody designed to mimic activated factor VIII by bridging factor IXa and factor X thus effecting hemostasis. Importantly, this drug eliminates the need for factor VIII and complications associated with inhibitor generation. Emicizumab has been approved for use in several countries including the United States and Japan for prophylaxis of bleeding episodes in hemophilia A with and without FVIII inhibitors. Therapy is also approved in the European Union for routine prophylaxis of bleeds in hemophilia A with inhibitors or severe hemophilia A without inhibitors. Unfortunately, emicizumab therapy presents unique challenges for routine and specialty coagulation tests currently used to monitor hemophilia A. In this review, hemophilia A is presented, the biochemistry of factor VIII is discussed, and the impact of the therapeutic agent emicizumab is highlighted.

Assessment of global coagulation function under treatment with emicizumab concomitantly with bypassing agents in haemophilia A with inhibitor (UNEBI Study): multicentre open-label non-randomised clinical trial

INTRODUCTION

Subcutaneous emicizumab prophylaxis substantially reduces bleeding episodes in patients with haemophilia A (PwHA) and factor VIII inhibitor. However, thrombotic events occurred in some PwHA with inhibitor who had received high cumulative doses of activated prothrombin complex concentrates at their breakthrough bleeds, when they were also given prophylactic emicizumab. After that, although the recommended guidance was proposed for bypassing agents (BPAs) therapy under emicizumab prophylaxis for haemostatic management, detailed investigation(s) is(are) required to elucidate the safe and appropriate dose of BPAs to use concomitantly with emicizumab prophylaxis.

METHODS AND ANALYSIS

In the UNEBI Study, 60 PwHA with inhibitor will be enrolled for a maximum duration of 3 years, and samples of 20 events following concomitant use of BPAs with emicizumab will be collected. An 'event' is defined as obtaining blood samples before and after administration of BPA when a breakthrough bleed or a surgical procedure occurs. The coagulation potential in the obtained samples will be measured by global coagulation assays. The primary endpoint is the degree of improvement in the maximum coagulation rate by clot waveform analysis (CWA) before and after administration of fixed-dose BPAs. This parameter obtained from CWA, which is triggered with an optimally diluted mixture of prothrombin time/activated partial thromboplastin time-reagents, is reported to be an excellent marker for assessing the degree of improvement in coagulation potential in emicizumab-treated plasma.

ETHICS AND DISSEMINATION

The UNEBI Study was approved by the Japan Certified Review Board of Nara Medical University. The results of the study will be communicated through publication in international scientific journals and presentations at (inter)national conferences.

TRIAL REGISTRATION NUMBER

jRCTs051190119.

Comprehensive blood coagulation potential in patients with acquired hemophilia A: retrospective analyses of plasma samples obtained from nationwide centers across Japan

Global coagulation potential was assessed in 59 patients with acquired hemophilia A (PwAHA) by clot waveform analysis (CWA) and/or thrombin and plasmin generation assay. Relationships between factor VIII activity (FVIII:C) and the parameters from CWA and T/P-GA in patients with congenital HA were compared by grading coagulation potential related to FVIII:C: T1 (FVIII:C < 1 IU/dL), T2 (1 ≤ , ≤ 5 IU/dL), T3 (5 < , 12 ≤ IU/dL), and T4 (12 < , ≤ 50 IU/dL). The median FVIII:C and inhibitor titers in PwAHA on admission were 3.3 IU/dL and 63.0 BU/mL, respectively, but global coagulation parameters corresponded to T1 or less. Median FVIII:C levels during follow-up in PwAHA were 1.7-9.6-6.7-40.0-21.7 IU/dL on days 0-14-28-56-93, respectively. CWA-based data corresponded to less than T2 until day 28, but more closely reflected FVIII:C after day 56. Peak thrombin was severely low (near T1) until day 28 and improved modestly after day 56 but remained less than T2. Peak plasmin was lower than T1 until day 56, and returned to T4 on day 93. In conclusion, global coagulation function in PwAHA was impaired to a greater extent than could be anticipated from assays of FVIII:C, until approximately 1 month after immunosuppression and treatment with FVIII-bypassing agents.

Inhibitor Index in the Clot Waveform Analysis-Based Mixing Test Differentiates among Hemophilia A without and with Inhibitors, and Lupus Anticoagulant

BACKGROUND

 The mixing test is used to identify the pathway to follow-up testing and is also useful for the investigation of lupus anticoagulant (LA) positivity. "To completely correct" indicates clotting factor deficiency, while "to not correct" indicates the presence of a clotting factor inhibitor including LA. "Index of circulation anticoagulant" and/or "percent correction" is used to interpret the results of mixing studies, but it does not accurately differentiate factor inhibitors from LA.

AIM

 To precisely differentiate hemophilia A (HA), HA with inhibitor (HA-inh), and LA using the clot waveform analysis (CWA)-based mixing test.

METHODS

 Plasma samples from HA, LA, and HA-inh including acquired HA were incubated with normal plasma in 9:1, 1:1, and 1:9 mix ratios. From activated partial thromboplastin time CWA at 0-minute (immediately) and 12-minute incubation, the ratios of CWA parameters at 12 minutes/0 minute (inhibitor index) were assessed.

RESULTS

 The inhibitor index values of CWA parameters obtained using the mixing test in a 1:1 ratio demonstrated a significant difference between HA-inh and LA but could not differentiate LA from HA-inh completely. Plasmas used for the mixing tests in 9:1 and 1:9 ratios were able to fully distinguish between HA-inh (>0.5 BU/mL) and LA. These indices significantly correlated with inhibitor titer below 40 BU/mL (r > 0.90), possibly estimating FVIII inhibitor titer from the inhibitor index. Plasmas in HA and LA could be distinguished by mixing in a 1:1 ratio at 0 minute (immediately).

CONCLUSION

 The inhibitor index from CWA-based mixing tests with a 12-minute incubation could differentiate among HA, HA-inh, and LA quickly.

Overall hemostasis potential and aPTT-clot waveform analysis as powerful laboratory diagnostic tools for identification of hemophilia A patients with unexpected bleeding phenotype

INTRODUCTION

Traditionally used laboratory methods do not always accurately reflect bleeding severity in hemophilia A (HA) patients. The ability of three global assays for identifying patients with unexpected bleeding phenotype was investigated.

METHODS

Overall hemostasis potential (OHP), aPTT-clot waveform analysis (aPTT-CWA), endogenous thrombin potential (ETP), FVIII activities, and prothrombin fragment 1 + 2 concentrations were measured in 62 HA patients (30 severe and 32 non-severe) and 27 male controls. Bleeding phenotype was determined using our proposed scoring system including age at first joint bleed, number of target joints, and number of joint/muscle bleeds per year. Bleeding score ≤ 4 defined patients with mild bleeding phenotype (N = 27); score ≥ 5 defined severe bleeding phenotype (N = 35).

RESULTS

The receiver operating characteristic analysis performed for distinguishing patients with severe and mild bleeding phenotype yielded following values of area under the curve: 0.910 (FVIII); 0.891 (aPTT-CWA parameter DELTA); 0.769 (OHP); and 0.634 (ETP). Unexpected bleeding phenotype was identified in 11/62 HA patients: 8/32 (25%) non-severe HA patients had severe, while 3/30 (10%) severe HA patients had mild bleeding phenotype, and global assays enabled the identification of all these patients. OHP and DELTA were revealed as the most reliable parameters for bleeding phenotype determination (10/11 and 9/11 unexpected results, respectively).

CONCLUSION

This study emphasizes OHP and aPTT-CWA as a powerful laboratory diagnostic tool in identifying HA patients with unexpected bleeding presentations, with the best results achieved by combining both assays. Global assays should not completely replace FVIII activity measurement but should be a part of the HA diagnostic algorithm.

Prediction of the haemostatic effects of bypassing therapy using comprehensive coagulation assays in emicizumab prophylaxis-treated haemophilia A patients with inhibitors

In emicizumab prophylaxis, the concomitant therapy using bypassing agents (BPAs) is required for breakthrough bleeding and invasive procedures with attention to thrombotic complications. To predict coagulant effects of BPAs in emicizumab-treated patients with haemophilia A (PwHA) with inhibitor (PwHAwI), blood samples from emicizumab-treated PwHAwI (n = 8) and PwHA without inhibitor (n = 2) in phase 1/2 and HAVEN 1 study, spiked with activated prothrombin complex concentrates (aPCC) or recombinant factor VIIa (rFVIIa) ex vivo, and blood samples from emicizumab-treated PwHAwI-receiving BPAs were analysed by Ca²⁺ -triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (CWA). Spiked aPCC, corresponded to 10-100 U/kg, markedly shortened ROTEM parameters beyond the normal range, while spiked rFVIIa, corresponded to 90-270 μg/kg, shortened them within near-normal range. Each of the spiked BPA-improved adjusted maximum coagulation velocity of CWA to within or near the normal range. In blood samples at post-infusion of aPCC (44-73 U/kg) or rFVIIa (79-93 μg/kg), the parameters of both assays improved to approximately the normal range. Taken together, ex vivo results of spiking tests in ROTEM and CWA, except aPCC spiking test in ROTEM, were relatively consistent with in vivo ones, and could usefully predict the coagulant effects of concomitant bypassing therapy for emicizumab-treated PwHAwI.

Global coagulation assays in hemophilia A: A comparison to conventional assays

BACKGROUND

Global assays measure the interactions of coagulants, anticoagulants, and platelets on thrombin generation and may reflect the comprehensive coagulation potential in patients with hemophilia better than conventional assays.

OBJECTIVES

The objectives of the current study were to investigate the value of global assays for measuring and monitoring the coagulation potential of patients with hemophilia A (HA).

PATIENTS/METHODS

Rotational thromboelastometry, thrombin generation assay (TGA), and activated partial thromboplastin time (APTT) clot waveform analysis were investigated in a cohort of patients with severe, moderate, and mild HA and compared with conventional assays.

RESULTS

The maximum velocity (MaxVel) parameter of modified thromboelastometry analysis, initiated by tissue factor and in the presence of corn trypsin inhibitor (CTI), had 92% sensitivity and 95% specificity for hemophilia diagnosis. The MaxVel also strongly correlated with factor VIII (FVIII) levels of patients with HA (r = .805, P < .0001). CTI improved the sensitivity of TGA, providing more accurate results. In particular, peak height parameter of platelet-rich plasma samples with CTI had a sensitivity and specificity of 100% and 94%, respectively, in all patients with HA. APTT clot waveform analysis minimum value of first derivative (Min1) and minimum value of second derivative (Min2) parameters (representing speed and acceleration of clot formation, respectively) were sensitive and correlated more strongly with FVIII levels than APTT clotting times did (Min1: r = 0.786, P < 0.0001; Min2: r = 0.759, P < 0.0001; APTT: r = -0.513, P = 0.001).

CONCLUSIONS

The sensitivity and specificity of the global assays was method dependent. Correlation between clinical end points and thrombin generation might also be valuable in the era of non-factor replacement therapy.

The First-Derivative Curve of the Coagulation Waveform Reveals the Cause of aPTT Prolongation

Clot waveform analysis based on activated partial thromboplastin time (aPTT) is reported to be a useful assay. We attempted to find beneficial parameters with the first-derivative curve. We examined 106 plasma samples with prolonged aPTT and analyzed the first-derivative curve statistically by dividing it into 6 groups (Lupus anticoagulant, Heparin, Direct oral anticoagulants, Factor VIII inhibitor, Hepatic dysfunctions and Factor deficiency). We obtained 7 coordinates for parameter measurement by analyzing the first-derivative curve and set 20 parameters including the velocity axis, the time axis, and area parameters. The distribution was checked by extracting each parameter that showed the most significant difference in the 6 groups. As a result, it was revealed that we could classify aPTT prolongation by using a combination of 3 parameters, the initial-to-peak gradient, the ratio initial-to-intermediate velocity/intermediate-to-peak velocity, and the initial-to-peak area size. We constructed a flowchart combining these 3 parameters and were able to discriminate 75% of the specimens. These parameters derived from the first-derivative curve of clot waveform analysis are useful tools to discriminate aPTT prolongation.

Elevated activated partial thromboplastin time-based clot waveform analysis markers have strong positive association with acute venous thromboembolism

Introduction

A hypercoagulable state is a predisposition for venous thromboembolism (VTE). The activated partial thromboplastin time (aPTT)-based clot waveform analysis (CWA) is a global haemostatic measure but its role in assessment of hypercoagulability and thrombotic disorders is uncertain. We aimed to study the changes of CWA parameters in acute VTE. We hypothesized that patients with acute VTE would demonstrate higher CWA values than control patients without VTE and having elevated CWA parameters is associated with acute VTE.

Materials and methods

Clot waveform analysis data from patients (N = 45) with objectively proven acute VTE who had an aPTT performed prior to initiation of anticoagulation were compared with controls (N = 111). The CWA parameters measured were min1, min2, max2 and delta change.

Results

While the mean aPTT between VTE patients and controls did not differ (P = 0.830), the mean CWA parameters were significantly higher among VTE patients than controls (min1, P < 0.001; min2, P = 0.001; max2, P = 0.002; delta change, P < 0.001). There were significantly more cases within the VTE group exhibiting CWA values above their reference intervals than the control group (all P < 0.001), with the odds ratios for VTE of 8.0, 5.2, 4.8 and 18.6 for min1, min2, max2 and delta change, respectively (all P < 0.001).

Conclusions

Patients with acute VTE had elevated aPTT-based CWA parameters than controls. Higher CWA parameters were significantly associated with acute VTE.

Emicizumab, the bispecific antibody to factors IX/IXa and X/Xa, potentiates coagulation function in factor XI-deficient plasma in vitro

Essentials Emicizumab mimics factor (F)VIIIa cofactor function, augments the intrinsic tenase activity. We assessed the emicizumab-driven hemostatic function in FXI-deficient plasmas. Emicizumab improved the coagulation potentials in severe FXI-deficient plasma. Emicizumab may provide a possibility for clinical application in patients with FXI deficiency. SUMMARY: Background Patients with factor (F)XI deficiency commonly present with markedly prolonged activated partial thromboplastin times (APTT), although bleeding phenotypes are heterogeneous. Emicizumab, a bispecific monoclonal antibody to FIX/FIXa and FX/FXa, mimics FVIIIa cofactor function on phospholipid (PL) surfaces. Antibody reactions were designed, therefore, to augment mechanisms during the propagation phase of blood coagulation. Aim To assess emicizumab-driven hemostatic function in FXI-deficient plasmas. Methods and Results Standard ellagic acid (Elg)/PL-based APTTs of different FXI-deficient plasmas (n = 13; FXI activity, < 1 IU dl-1 ) were markedly shortened dose dependently by the presence of emicizumab. To further analyze the effects of emicizumab, clot waveform analysis (CWA) in FXI-deficient plasmas with emicizumab, triggered by tissue factor (TF)/Elg demonstrated improvements in both clot times, reflecting the initiation phase, and coagulation velocity, which represents the propagation phase. Emicizumab also enhanced the TF/Elg-triggered thrombin generation in FXI-deficient plasmas dose-dependently although the degree of enhancement varied in individual cases. Thrombin generation with either FVII-deficient plasma or FIX-deficient plasma treated with anti-FXI antibody showed little or no increase by the co-presence of emicizumab, suggesting that the accelerated thrombin generation in FXI-deficient plasmas by emicizumab should depend on the FIXa-involved coagulation propagation initially triggered by FVIIa/TF. The ex vivo addition of emicizumab to whole blood from three patients with severe FXI deficiency demonstrated modest, dose-dependent improvements in Ca2+ -triggered thromboelastograms (NATEM mode). Conclusion Emicizumab appeared to improve coagulation function in severe FXI-deficient plasma, and might provide possibilities for clinical application in patients with FXI deficiency.

Dynamic evaluation of hemostasis in the acute phase of Kawasaki disease using comprehensive coagulation functional assays

INTRODUCTION

Kawasaki disease (KD) is a systemic vasculitis involving coronary arteries, sometimes resulting in aneurysms and myocardial infarction. Hyper-coagulability in the acute-phase of KD is indicated in some circumstances based on changes of individual clotting factors. Comprehensive coagulation assays, clot waveform analysis (CWA) and thrombin/plasmin generation assay (T/P-GA), have been developed to assess physiological hemostasis, but these techniques have not been applied in KD.

METHODS

We utilized both assays to analyze coagulation function in KD children (n = 42) prior to intravenous-immunoglobulin (IVIG) treatment (Pre), 1-week (1W) and 1-month (1M) post-IVIG.

RESULTS

In CWA, the clot time (CT) pre-treatment was prolonged, and was significantly shortened at 1W and 1M. However, the maximum coagulation velocity (|min1|) and acceleration (|min2|) were ~2-fold greater relative to controls, indicating an overall hypercoagulable tendency. These parameters were related to fibrinogen concentration, and were decreased at 1W and declined to normal at 1M. In T/P-GA, the endogenous potentials of thrombin and plasmin were greater relative to control at each of three time-points, and measurements at 1W were greater than those Pre-treatment. The ratios of TG and PG relative to control were similar, however, suggesting well-balanced dynamic coagulation and fibrinolysis. In non-responders to IVIG, the |min1| and |min2| measurements were greater than those in responders at 1W and 1M, suggesting that non-responders remained hypercoagulable after primary treatment.

CONCLUSION

The coagulation data observed in KD were consistent with hypercoagulability, although fibrinolytic function appeared to be well-balanced. Comprehensive assays of this nature could provide valuable information on coagulation potential in KD.

Retrospective comparison of standard clotting tests and novel clot waveform parameters in dogs using the turbidimetric ACL-TOP CTS 300 coagulation analyzer

Clot waveforms are generated by coagulation analyzers, such as the ACL-TOP, that utilize photo-optical turbidimetric methods to measure prothrombin time (PT) and activated partial thromboplastin time (aPTT), which are standard clotting tests (SCTs). Additional quantitative clot waveform analysis (CWA) parameters include maximum velocity of the PT curve (PT1d), maximum acceleration of the aPTT curve (aPTT2d), and their change in optical density (ODdelta). We explored the potential for CWA to contribute unique information compared to SCTs and quantitative fibrinogen assay (QFA) in dogs with clinical indications for laboratory evaluation of coagulation. We retrospectively evaluated the frequency and agreement between normal, high, and low values of CWA and SCTs for 203 dogs relative to reference intervals (RIs). Most dogs had SCTs within RIs, but most CWA values were high regardless of whether SCT values were within, below, or above the RI. Agreement between SCTs and CWA was slight (kappa <30%). Clinically significant bleeding was noted in 28 of 203 (14%) dogs. SCTs were not different between bleeders and non-bleeders. Median QFA, PT1d, aPTTdelta, and aPTT2d values were statistically significantly higher than RIs in non-bleeders compared to bleeders, whose median values were not below RI. Compared with SCTs, CWA identified differences between the 2 groups. However, wide overlap between the 2 groups limits the use of CWA to clinically discriminate between bleeders and non-bleeders in a heterogeneous population of dogs. Further studies on the diagnostic utility of CWA in coagulopathic dogs are needed.

Modified clot waveform analysis to measure plasma coagulation potential in the presence of the anti-factor IXa/factor X bispecific antibody emicizumab

Essentials The activated partial prothrombin time (aPTT) cannot predict the activity of emicizumab (Emi). Adjusted clot waveform analyses using a prothrombin time (PT)/aPTT initiator were developed. Activity of Emi in the co-presence of factor VIII or bypassing agents was quantified. This assay is useful for assessing coagulation potential in Emi-treated hemophilia A.

SUMMARY

Background Emicizumab is an anti-activated factor IX/FX bispecific antibody that mimics activated FVIII cofactor function. Emicizumab does not require activation by thrombin, and its effect on shortening the activated partial thromboplastin time (APTT) is much greater than that of FVIII. Therefore, the APTT has limited utility in hemophilia A (HA) patients treated with emicizumab. Aim To evaluate the global coagulation potential of emicizumab. Methods Clot waveform analysis (CWA) with prothrombin time (PT)/APTT mixed reagents was used to define hemostatic monitoring protocols in HA patients. A modified parameter, adjusted-|min1| (Ad|min1|), was developed. Maximum and minimum percentage transmittance were defined as 100% and 0% in the precoagulation and postcoagulation phases, respectively. Ad|min1| was calculated as an index of the maximum velocity of the coagulation process. Results Ad|min1| obtained with mixed-trigger reagent (PT/APTT/buffer, 1 : 15 : 135) in the presence of emicizumab optimally corresponded to the conversion rate estimated in animals; 0.2-0.4 IU dL-1 equivalent FVIII per 1 μg mL-1 emicizumab). Ex vivo addition of emicizumab to HA plasma with or without inhibitors resulted in concentration-dependent increases in Ad|min1|, with some individual variations. The addition of various concentrations of FVIII to HA plasma mixed with emicizumab resulted in dose-dependent increases in Ad|min1|. Similarly, mixtures of activated prothrombin complex concentrate and emicizumab added to HA plasma resulted in dose-dependent increases in Ad|min1|. In contrast, enhanced coagulation potential appeared to be better defined by the clot time than by Ad|min1| in experiments using recombinant activated FVII. Conclusion The PT/APTT reagent-triggered adjusted CWA could provide a useful means of assessing global coagulation potential in emicizumab-treated HA patients, with enhanced activity neither masking nor being masked by FVIII or bypassing agents.

Clot waveform analysis: Where do we stand in 2017?

Analysis of the optical waveform generated during global coagulation assays, such as activated partial thromboplastin time and prothrombin time, can provide much precious information on the global coagulation state of the plasma sample tested, in addition to a single clotting time. Many studies have been published concerning patient diagnosis and management in haemophilia A, and in the early diagnosis and prognosis of disseminated intravascular coagulation and sepsis. However, many other works have also been published on further potential clinical applications such as lupus anticoagulant diagnosis and anticoagulant monitoring. Altogether, these publications have demonstrated the ability for clot waveform analysis (CWA) to improve patient management, especially as this tool is inexpensive, rapid and readily available on coagulation analysers with optical detection systems. By an extensive review of the literature related to studies performed on CWA, this publication aims at providing a review of current knowledge in this specific field, ranging from research data to potential clinical applications and future trends.