Management of thrombotic thrombocytopenic purpura

Guidance-Based Appropriateness of Hemostasis Testing in the Acute Setting

In this review, we aim to highlight the extent of inappropriate hemostasis testing and provide practical guidance on how to prevent it. We will focus on the acute setting, including but not limited to the emergency department and intensive care unit. To this end, we will first discuss the significance of inappropriateness, in the general context of laboratory medicine. This includes acknowledging the importance of the phenomenon and attempting to define it. Next, we describe the harmful consequences of inappropriate testing. Finally, we focus on the inappropriate use of hemostasis testing in the acute setting. The second section describes how interventions-in particular, the implementation of guidance for testing-can efficiently reduce inappropriateness. In the third section, we summarize the available recommendations for rational use of hemostasis testing (platelet count, activated partial thromboplastin time, prothrombin time/international normalized ratio, fibrinogen, thrombin time, D-dimer, anti-Xa assay, antithrombin, ADAMTS13 activity, antiheparin-PF4 antibodies, viscoelastometric tests, coagulation factors, and platelet function testing), as supported by guidelines, recommendations, and/or expert opinions. Overall, this review is intended to be a toolkit in the effort to promote the appropriate use of hemostasis testing. Hopefully, the new In Vitro Diagnostic Medical Device Regulation (EU) 2017/746 (IVDR) should help in improving the availability of evidence regarding clinical performance of hemostasis assays.

N-Acetylcistein for thrombotic thrombocytopenic purpura: an observational case series study

Acquired thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder. N-Acetylcysteine (NAC) rapidly degrades ultra-large von Willebrand factor multimers by disrupting the disulfide bonds. We report a series of twelve consecutive patients diagnosed with acquired TTP successfully treated with high-dose NAC (150 mg/kg/day) in combination with plasma exchange and steroids. Eight patients also received rituximab. Two patients presented refractory TTP. All patients achieved a quick clinical response in a median time of 5.5 days after starting NAC and are alive after a median follow-up of 29 months. The treatment was feasible and well tolerated. These data provide further evidence of the potential benefit and safety of adding NAC to the standard of care.

The efficacy and safety of caplacizumab in Japanese patients with immune-mediated thrombotic thrombocytopenic purpura: an open-label phase 2/3 study

Caplacizumab is an anti-von Willebrand factor humanized single-variable-domain immunoglobulin fragment whose efficacy and safety in immune-mediated thrombotic thrombocytopenia purpura (iTTP) have been demonstrated in international studies. This prospective, open-label phase 2/3 study evaluated caplacizumab 10 mg administered daily during plasma exchange and for 30 days afterward, in combination with immunosuppressive treatment, in Japanese adults with a clinical diagnosis of iTTP (new or recurrent). The primary endpoint was prevention of iTTP recurrence; key secondary endpoints included time to platelet count response, time to organ damage normalization, and safety. Among 21 treated patients, 1 of 15 (6.7%) evaluable patients developed iTTP recurrence. Median time to normalization was 2.79 days for platelet count and 2.65 days for organ damage markers (n = 15). Treatment-emergent adverse events (TEAEs) were mostly mild to moderate in severity; the most frequently reported caplacizumab-related TEAEs were increased alanine aminotransferase, epistaxis, and gastrointestinal hemorrhage (all in 9.5% of patients). At least one bleeding event was reported in 7 of 21 patients (33%). Caplacizumab was effective in Japanese patients with iTTP, with a low rate of iTTP recurrence, rapid normalization of platelet counts and organ damage markers, and no unexpected TEAEs. Trial registration: ClinicalTrials.gov identifier, NCT04074187.

Von Willebrand factor assays in patients with acquired immune thrombotic thrombocytopenia purpura treated with caplacizumab

Acquired immune thrombotic thrombocytopenic purpura (iTTP) is a rare disease with a poor prognosis if undiagnosed. It is caused by autoantibody production to the von Willebrand factor (VWF) cleaving protease, A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). Caplacizumab, an immunoglobulin directed to the platelet glycoprotein Ibα receptor of VWF, has been reported to induce quicker resolution of iTTP compared to placebo. The laboratory measurement of VWF activity was significantly reduced in clinical trials of caplacizumab. Several VWF assays are available in the UK and this study investigated whether differences in VWF parameters were present in 11 patients diagnosed with iTTP and treated with daily caplacizumab. Chromogenic factor VIII activity, VWF antigen, collagen binding activity, VWF multimers and six VWF activity assays were measured prior to caplacizumab therapy and on several occasions during treatment. VWF antigen and collagen binding activity levels were normal or borderline normal in all patients. Ultra-large molecular weight multimers were present in all patients following treatment. VWF activity assays were normal or reduced during treatment, but this was reagent and patient dependant. In the unusual scenario of a caplacizumab-treated patient requiring measurement of VWF activity, it is important that laboratories understand how their local reagents perform as results cannot be predicted.

[Spontaneous adrenal hematomas. Retrospective analysis of 20 cases from a tertiary center]

INTRODUCTION

Spontaneous adrenal hemorrhages (AH) are a rare condition with no consensus about their management.

METHODS

Patients were identified using the Medicalization of the Information System Program database, imaging software and a call for observations to internists, intensivists and obsetricians working at our institution. Adult patients whose medical records were complete and whose diagnosis was confirmed by medical imaging were included.

RESULTS

From 2000 to 2007, 20 patients were identified, including 15 were women. The clinical onset of AH was non-specific. In five cases, AH occurred during pregnancy; four of them were unilateral and right sided. The etiology of the other fifteen (bilateral adrenal hemorrhage in 11) were as follows: antiphospholipid syndrome (n=8), heparin-induced thrombocytopenia (n=4), essential thrombocythemia (n=3), spontaneous AH due to oral anticoagulants (n=1), complication of a surgical act (n=3), and sepsis (n=3). In seven cases, two causes were concomitant. The diagnosis of AH was often confirmed by abdominal CT. An anticoagulant treatment was initiated in 16 cases. Ten of the eleven patients presenting with bilateral adrenal hematomas were treated using a long-term substitute opotherapy. One patient died because of a catastrophic antiphospholipid syndrome.

CONCLUSION

The clinical onset of HS is heterogeneous and non-specific. The confirmatory diagnosis is often based on abdominal CT. The search for an underlying acquired thrombophilia is essential and we found in this study etiological data comparable to the main series in the literature. Adrenal insufficiency is most of the time definitive in cases of bilateral involvement.

Development and validation of a prediction model (AHC) for early identification of refractory thrombotic thrombocytopenic purpura using nationally representative data

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare and life-threatening haematological emergency. Although therapeutic plasma exchange together with corticosteroids achieve successful outcomes, a considerable number of patients remain refractory to this treatment and require early initiation of intensive therapy. However, a method for the early identification of refractory iTTP is not available. To develop and validate a model for predicting the probability of refractory iTTP, a cohort of 265 consecutive iTTP patients from 17 large medical centres was retrospectively identified. The derivation cohort included 94 patients from 11 medical centres. For the validation cohort, we included 40 patients from the other six medical centres using geographical validation. An easy-to-use risk score system was generated, and its performance was assessed using internal and external validation cohorts. In the multivariable logistic analysis of the derivation cohort, three candidate predictors were entered into the final prediction model: age, haemoglobin and creatinine. The prediction model had an area under the curve of 0.886 (95% CI: 0.679-0.974) in the internal validation cohort and 0.862 (95% CI: 0.625-0.999) in the external validation cohort. The calibration plots showed a high agreement between the predicted and observed outcomes. In conclusion, we developed and validated a highly accurate prediction model for the early identification of refractory iTTP. It has the potential to guide tailored therapy and is a step towards more personalized medicine.

Thrombotic Thrombocytopenic Purpura Masquerading as Acute Ischemic Stroke

Thrombotic thrombocytopenic purpura (TTP) is a hematologic disorder that results in widespread clotting due to a deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) protease. This leads to excessive von Willebrand factor (VWF) protein-platelet multimers. Due to platelet consumption, platelet levels fall, resulting in thrombocytopenia. We examined a case of a 31-year-old female with no significant medical history who presented with expressive aphasia and paresthesias and was sent to the Emergency Department for a stroke workup. Imaging was negative for ischemic or hemorrhagic stroke; however, a complete blood count (CBC) was consistent with anemia and thrombocytopenia, resulting in a high suspicion for TTP. She was admitted to the intensive care unit and given fresh frozen plasma and packed red blood cells. Plasma exchange therapy was initiated, and her aphasia and paresthesias began to improve. The ADAMTS13 level returned at less than 5%, which prompted the initiation of rituximab therapy. During her 36-day hospital stay, she continued to receive daily steroids and plasma exchange and a total of four courses of rituximab. Her platelets steadily climbed, and she was discharged with instructions to follow up with outpatient hematology. TTP is a thrombotic microangiopathy that results in microscopic blood clots anywhere in the body, including the cerebral arteries. This results in the neurologic abnormalities that are often seen in TTP. Because TTP is a rare disease, treatment modalities are still scarce but include steroids, plasma exchange therapy, and rituximab. Novel therapies are on their way, one being caplacizumab, a monoclonal antibody that inhibits VWF from interaction with glycoprotein 1b. A concern highlighted by this case is the exclusion criteria for the administration of tissue plasminogen activator (TPA). As this patient presented with stroke symptoms and a negative head CT, TPA would have been administered had a CBC not returned showing evidence of TTP. This highlights the importance of strict adherence to the American Heart Association/American Stroke Association guidelines that include ensuring that the platelet count is >100,000 prior to the initiation of TPA.

Thrombotic thrombocytopenic purpura associated with pesticides: A report of 4 cases and literature review

Thrombotic thrombocytopenic purpura (TTP) is a disease characterized by the presence of microangiopathic hemolytic anemia (MAHA) and thrombocytopenia, caused by the congenital or acquired decrease of the enzyme activity which degrades unusual large vWF multimers. There is no identifiable cause in half of the acquired TTP cases. Herein, we report four possible pesticide-related cases with decreased ADAMTS13 enzyme activity, increased titer of ADAMTS13 inhibitor and typical clinical and laboratory presentation.

Real-World Budget Impact of Listing a Biosimilar of Rituximab

BACKGROUND

The approval of new biosimilars by national health agencies is expected to generate significant cost savings for health care systems. This is particularly the case with the biosimilar of rituximab approved for the Canadian market in 2019. However, several uncertainties remain regarding utilization of this agent.

OBJECTIVES

To determine the proportion of total annual drug expenses for each indication for rituximab in the hospital setting and to determine potential savings related to introduction of a biosimilar.

METHODS

A budget impact analysis was performed through 3 real-world scenarios, based on data obtained from a large university teaching hospital for a 12-month period.

RESULTS

This study involved data for 420 patients. Annual expenses for rituximab for all indications represented 7.7% of total annual drug spending for the hospital, of which 5.0% was related specifically to indications approved by Health Canada. More than 6% of the annual drug expenses was attributable to the use of rituximab for oncologic indications, including 1.8% for uses not approved by Health Canada. Overall, each 10% reduction in the price of a biosimilar of rituximab (relative to the reference rituximab) would result in annual savings of about 0.8% of total drug expenses in the hospital if a biosimilar was used for all real-world indications, whether approved by Health Canada or not.

CONCLUSIONS

The introduction of a biosimilar of rituximab to the Canadian market would generate significant savings. To properly assess the potential savings that this agent could generate in the limited budget environment of a hospital, it seems important to consider all of the indications for which it could be used.

Amotosalen-inactivated fresh frozen plasma is comparable to solvent-detergent inactivated plasma to treat thrombotic thrombocytopenic purpura

BACKGROUND

Therapeutic Plasma Exchange (TPE) is the primary therapy of immune-mediated Thrombotic Thrombocytopenic Purpura (iTTP). Efficacy and safety data for TPE of iTTP have been assessed with Quarantine and Solvent-Detergent inactivated (SD) plasma. Here, amotosalen-UVA pathogen inactivated (AI) plasma, also in routine use, was evaluated in iTTP.

METHODS

We conducted a retrospective review of iTTP cases prospectively reported to the French national registry (2010-2013). Cases reviewed underwent TPE with ≥70% of either AI or SD plasma. The primary endpoint was time to platelet count recovery; secondary endpoints were related to follow-up (sustained remission, relapses, flare-ups and refractoriness).

RESULTS

30 Test patients were identified in the AI group which could be timely matched to 40 Control patients in the SD group. The groups were fairly comparable for clinical presentation. Major findings were: (i) iTTP patients were exposed to lower plasma volumes in the AI group than in the SD group; (ii) Recovery rates were comparable between the groups. Median time to platelet count recovery (>150 × 10⁹/L) trended to be shorter in the AI group though non significantly. Tolerance of AI vs SD plasma was of comparable frequency and severity in either group.

CONCLUSION

TPE with Amotosalen-inactivated plasma demonstrated therapeutic efficacy and tolerability for iTTP patients. In view of the retrospective design, confirmation of these results is required in larger prospective studies.

Expert statement on the ICU management of patients with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is fatal in 90% of patients if left untreated and must be diagnosed early to optimize patient outcomes. However, the very low incidence of TTP is an obstacle to the development of evidence-based clinical practice recommendations, and the very wide variability in survival rates across centers may be partly ascribable to differences in management strategies due to insufficient guidance. We therefore developed an expert statement to provide trustworthy guidance about the management of critically ill patients with TTP. As strong evidence was difficult to find in the literature, consensus building among experts could not be reported for most of the items. This expert statement is timely given the recent advances in the treatment of TTP, such as the use of rituximab and of the recently licensed drug caplacizumab, whose benefits will be maximized if the other components of the management strategy follow a standardized pattern. Finally, unanswered questions are identified as topics of future research on TTP.

Caplacizumab: a change in the paradigm of thrombotic thrombocytopenic purpura treatment

Introduction: Immune thrombotic thrombocytopenic purpura (iTTP) is an immune-mediated deficiency in von Willebrand factor-cleaving protease ADAMTS13 allowing unrestrained adhesion of von Willebrand factor multimers to platelets and microthrombosis. Caplacizumab, an anti-von Willebrand factor humanized, bivalent single-domain nanobody preventing its binding to the platelet has been investigated and approved for use in the treatment of iTTP. Areas covered: The purpose of this article is to summarize the available clinical data on the efficacy and safety of caplacizumab in iTTP and to provide our opinion on the place of caplacizumab in current treatment regimens. Expert opinion: Caplacizumab is a new drug with a complementary mechanism of action with respect to the standard available therapeutics. It demonstrated efficacy in clinical trials through a faster platelet count normalization and protection of patients from exacerbations and refractoriness. Caplacizumab is well tolerated with minor bleeds as the most important side effect. The efficacy of caplacizumab now needs to be assessed in real-life but definitely, this drug opens hope for a significant improvement in iTTP prognosis at the very early, critical step of the disease.

Clinical pharmacology of caplacizumab for the treatment of patients with acquired thrombotic thrombocytopenic purpura

Introduction: Caplacizumab is a humanized anti-von Willebrand Factor (vWF) Nanobody® for the treatment of acquired Thrombotic Thrombocytopenic Purpura (aTTP). Caplacizumab targets the A1-domain of vWF, inhibiting the interaction between vWF and platelets. Clinical studies conducted in aTTP patients confirmed the rapid and sustained complete suppression of the vWF activity using an initial intravenous dose of 10 mg, and a maintenance subcutaneous 10 mg daily dosing regimen, with corresponding favorable efficacy and safety profiles. Areas covered: The pharmacokinetics of caplacizumab are non-linear, characterized by a target-mediated disposition and the exposure is dependent upon drug and target concentration over time. The pharmacokinetics of caplacizumab are predictable when considering the turn-over of the circulating vWF and its modulation by the drug over time. Renal and hepatic impairment are not expected to influence the exposure to the drug, and no direct or indirect drug-drug pharmacokinetic interactions are anticipated based on the mechanism of action and the specificity of the pharmacodynamic effect of caplacizumab. Expert opinion: Caplacizumab prevents the interaction between vWF and platelets, offering a direct and rapid therapeutic intervention to stop microthrombosis. The combination of caplacizumab with plasma exchange and immunosuppression represents an important, potentially life-saving advance in the treatment of aTTP patients.

Hematological Malignancies and Arterial Thromboembolism

Established guidelines exist for prevention and treatment of venous thromboembolism in hematological malignancies, but none for arterial thromboembolism. However, arterial and venous thromboembolism share the same provoking features—including altered procoagulant factors and defective fibrinolytic system. The morbidity for arterial thromboembolism is increasing in hematological malignancies, with the advent of immunomodulatory and targeted therapy. However, survival rate for hematological malignancy is improving. Consequently, as patients with hematological malignancies live longer, comorbidities including diabetes, hypertension and dyslipidemia, may accentuate arterial thrombosis. Thus far, the scientific literature on prophylaxis and treatment for arterial thromboembolism in hematological malignancies is limited. This review highlights the pathogenesis, incidence and clinical features of arterial thromboembolism in hematological malignancies.

HELLP Syndrome, Thrombotic Thrombocytopenic Purpura or Both: Appraising the Complex Association and Proposing a Stepwise Practical Plan for Differential Diagnosis

Both thrombocytopenia and microangiopathic hemolytic anemia (TMA) are seen in thrombotic thrombocytopenic purpura (TTP) and HELLP syndrome among other disorders during pregnancy. Although both share backgrounds of endothelial injury and microvascular thrombi and some clinical features, yet, they have different etiologies and courses. In late pregnancy, differentiating between these two pathologies can be extremely difficult due to the immense overlap in clinical and laboratory manifestations and this becomes only possible with the use of specific markers as ADAMTS-13, when available. Hereby, we describe three cases that may exemplify the complex association between PE/HELLP syndrome and TTP. The first case presented with PE/HELLP syndrome and deteriorated postpartum to improve on plasmapheresis. The second case was a known TTP patient who developed superimposed PE/HELLP at 27 weeks gestation which necessitated emergent delivery. The third was a case of preeclampsia that progressed to HELLP syndrome on day 2 postpartum but 3 days later was complicated by TTP. HELLP syndrome and TTP can co-exist, but can also complicate one another. In the absence of instantaneous results of ADAMTS-13 and when diagnosis with clinical judgement alone cannot be done with certainty, a short trial-plasmapheresis could be attempted with close observation of the immediate response. This stepwise approach might prove to be a valuable tool when integrated in the usual workup of clinical and laboratory evaluation both before and after delivery.