Cerebral venous sinus thrombosis associated with SRA-negative heparin-induced thrombocytopenia: case report.

BACKGROUND: There are very few documented reports in literature of cerebral venous sinus thrombosis (CVST) caused by immune-mediated heparin-induced thrombocytopenia (HIT). Further, there are very few reports of false negative serotonin release assays (SRAs) when testing for immune-mediated HIT. CASE PRESENTATION: We present a case of a 60- year-old male with recent unfractionated heparin administration for venous thromboembolism prophylaxis, an elevated 4T score of 5 and acute CVST in which immune-mediated HIT was suspected. The enzyme-linked immunosorbent assay (ELISA) screening assay was positive for PF4 antibodies and subsequent reflexive SRA testing was negative. However, given the clinical picture, a false-negative SRA was suspected (and eventually confirmed), prompting use of the alternative PF4-dependent p-selectin expression assay (PEA) which was confirmed to be positive. The patient was successfully managed with a bivalirudin infusion and eventually transitioned to apixaban. CONCLUSION: It is uncommon for immune-mediated HIT with thrombosis to manifest as CVST. Similarly, false-negative SRA is uncommon in immune-mediated HIT. Take-away lessons from our case report include considering HIT in CVST patients with an elevated 4T score and considering the entire clinical picture and degree of suspicion for HIT when interpreting negative HIT testing results. The PEA, in conjunction with the 4Ts score, may be considered as an alternate diagnostic assay for HIT.

Analysis of College of American Pathologists von Willebrand Factor Proficiency Testing Program.

Von Willebrand factor (VWF) level and/or function is altered in von Willebrand disease (VWD), the most common heritable bleeding disorder worldwide. Laboratory assessment of VWF is continually evolving. Historically, the primary method for the assessment of VWF platelet-binding activity was the ristocetin cofactor assay (VWF:RCo). Contemporary alternative measures of VWF platelet-binding activity include VWF:GPIbR (recombinant; using ristocetin), VWF:GPIbM (recombinant; gain-of-function mutant), and monoclonal antibody. Recently, the American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia collaboration issued guidelines recommending the use of newer assays of VWF platelet-binding activity (VWF: GPIbM, VWF: GPIbR) over VWF:RCo, given known limitations of the VWF:RCo assay. Despite this recommendation, the newer VWF:GPIbM and VWF:GPIbR assays are not United States Food and Drug Administration cleared, limiting their availability in the United States. We sought to assess assay utilization trends, agreement of VWF testing methods, and imprecision of VWF testing (based on assigned sample type) from the College of American Pathologists Proficiency Testing Surveys. The analysis confirms that, while VWF antigen testing has low imprecision, the various VWF activity assays have significant interassay variability, with VWF:RCo showing greater imprecision than the newer GPIb-binding assays. The overall trends in assay utilization reflect the barriers to complete compliance with modern VWD diagnostic guidelines in North America.

Analysis of College of American Pathologists von Willebrand Factor Proficiency Testing Program.

Von Willebrand factor (VWF) level and/or function is altered in von Willebrand disease (VWD), the most common heritable bleeding disorder worldwide. Laboratory assessment of VWF is continually evolving. Historically, the primary method for the assessment of VWF platelet-binding activity was the ristocetin cofactor assay (VWF:RCo). Contemporary alternative measures of VWF platelet-binding activity include VWF:GPIbR (recombinant; using ristocetin), VWF:GPIbM (recombinant; gain-of-function mutant), and monoclonal antibody. Recently, the American Society of Hematology, International Society on Thrombosis and Haemostasis, National Hemophilia Foundation, and World Federation of Hemophilia collaboration issued guidelines recommending the use of newer assays of VWF platelet-binding activity (VWF: GPIbM, VWF: GPIbR) over VWF:RCo, given known limitations of the VWF:RCo assay. Despite this recommendation, the newer VWF:GPIbM and VWF:GPIbR assays are not United States Food and Drug Administration cleared, limiting their availability in the United States. We sought to assess assay utilization trends, agreement of VWF testing methods, and imprecision of VWF testing (based on assigned sample type) from the College of American Pathologists Proficiency Testing Surveys. The analysis confirms that, while VWF antigen testing has low imprecision, the various VWF activity assays have significant interassay variability, with VWF:RCo showing greater imprecision than the newer GPIb-binding assays. The overall trends in assay utilization reflect the barriers to complete compliance with modern VWD diagnostic guidelines in North America.

Therapeutic plasma exchange taper does not decrease exacerbations in immune thrombotic thrombocytopenic purpura patients.

BACKGROUND: Despite rapid and intensive treatments with therapeutic plasma exchange (TPE) and immunosuppression, immune thrombotic thrombocytopenic purpura (TTP) patients are at risk of disease exacerbation, i.e., early recurrence of TTP within 30 days of achieving treatment response. TPE taper, a practice of performing additional TPE procedures after achieving treatment response, is commonly performed for decreasing exacerbations, although no evidence supports this practice. STUDY DESIGN AND METHODS: In this prospective observational investigation over four years, our center switched its standard of care for treating all TTP patients from not performing TPE taper after achieving treatment response (i.e., no-taper cohort) to performance of TPE taper (i.e., yes-taper cohort) to characterize impacts on exacerbations. Continuous and categorical data were analyzed by Mann-Whitney, Fisher's exact, and log-rank tests; significance was defined as p < 0.05. RESULTS: The two cohorts were well matched and had no significant differences in demographics, presentation laboratory values, or TTP history (p > 0.05 for all). The yes-taper cohort of 26 patients with 29 consecutive episodes did not have a significantly different exacerbation rate from the no-taper cohort of 24 patients with 27 consecutive episodes (exacerbation rates of 37.9% vs. 33.3%, respectively; p = 0.78); however, treatment-related complications directly attributed to the TPE procedures, blood products, or central venous catheters were significantly greater in the yes-taper cohort (nine vs. one events, respectively; p = 0.01). CONCLUSION: Since TPE taper did not reduce exacerbations in our TTP patients, we no longer advocate for TPE taper and have reverted to our original standard of care.

Von Willebrand factor as a thrombotic and inflammatory mediator in critical illness.

The endothelial exocytosis of high-molecular-weight multimeric von Willebrand factor (vWF) may occur in critical illness states, including trauma and sepsis, leading to the sustained elevation and altered composition of plasma vWF. These critical illnesses involve the common process of sympathoadrenal activation and loss of the endothelial glycocalyx. As a prothrombotic and proinflammatory molecule that interacts with the endothelium, the alterations exhibited by vWF in critical illness have been implicated in the development and damaging effects of downstream pathologies, such as disseminated intravascular coagulation and systemic inflammatory response syndrome. Given the role of vWF in these pathologies, there has been a recent push to further understand how the molecule may be involved in the pathophysiology of related diseases, such as trauma-induced coagulopathy and acute renal injury, which are also known to develop secondarily to critical illness states. Elucidation of the role of vWF across the broader spectrum of generalized pathologies may provide a basis for the development of novel preventative and restorative measures, while also bolstering the scaffold of more widely used treatments, such as the administration of plasma-containing blood products.

Therapeutic plasma exchange and intravenous immune globulin in the treatment of heparin-induced thrombocytopenia: A systematic review.

BACKGROUND: Immunomodulatory strategies in heparin-induced thrombocytopenia (HIT) include the use of intravenous immune globulin (IVIG) and therapeutic plasma exchange (TPE). The optimal application of these therapies is unknown and outcomes data are limited. We investigated treatment categories and laboratory and clinical outcomes of IVIG and/or TPE in HIT with a systematic literature review. STUDY DESIGN AND METHODS: We searched MEDLINE, Embase, and Web of Science through December 2019 for studies combining controlled vocabulary and keywords related to thrombocytopenia, heparin, TPE, and IVIG. The primary outcome was treatment indication. Secondary outcomes were platelet recovery, HIT laboratory parameters, heparin re-exposure, and post-treatment course. Case-level data were analyzed by qualitative synthesis. RESULTS: After 4241 references were screened, we identified 60 studies with four main categories of IVIG and/or TPE use as follows: (a) treatment of refractory HIT (n = 35; 31%); (b) initial therapy (n = 45; 40%); (c) cardiopulmonary bypass surgery (CPB; n = 30; 27%); and (d) other (n = 2; 2%). IVIG was most commonly used for the treatment of refractory HIT while TPE was primarily used to facilitate heparin exposure during CPB. Both IVIG and TPE were equally used as initial therapy. Heparin re-exposure occurred without thrombotic event in 29 TPE-treated patients and three IVIG-treated patients. CONCLUSION: In patients with HIT, both TPE and IVIG are used for initial therapy or treatment of refractory HIT. However, TPE is more commonly used in patients undergoing CPB. Prospective studies may help clarify which treatment is indicated in HIT population subsets.

Traumatic injury results in prolonged circulation of ultralarge von Willebrand factor and a reduction in ADAMTS13 activity.

BACKGROUND: Increases in plasma von Willebrand Factor (VWF) levels, accompanied by decreases in the metalloprotease ADAMTS13, have been demonstrated soon after traumatic injury while downstream effects remain unclear. STUDY DESIGN AND METHODS: A cohort of 37 injured trauma patients from a randomized control trial investigating the use of prehospital plasma transfusion were analyzed for activity and antigen levels of ADAMTS13 and VWF at 0 and 24 hours after admission. Relevant clinical data were abstracted from the medical records. Trauma patient plasma was analyzed via agarose gel electrophoresis to evaluate the effects of injury on VWF multimer composition compared to healthy controls. RESULTS: von Willebrand factor levels were elevated at presentation (189% [110%-263%] vs. 95% [74%-120%]), persisting through 24 hours (213% [146%-257%] vs. 132% [57%-160%]), compared to healthy controls. Ultralarge VWF (UL-VWF) forms were elevated in trauma patients at both 0 and 24 hours, when compared to pooled normal plasma (10.0% [8.9%-14.3%] and 11.3% [9.1%-21.2%], respectively, vs. 0.6%). Circulating plasma ADAMTS13 activity was decreased at 0 hours (66% [47%-86%] vs. 100% [98%-100%]) and at 24 hours (72.5% [56%-87.3%] vs. 103% [103%-103%]) in trauma patients. ADAMTS13 activity independently predicted the development of coagulopathy and correlated with international normalized ratio, thromboelastography values, injury severity, and blood product transfusion. CONCLUSION: Traumatic injury is associated with acute coagulopathy that is characterized by increased UL-VWF multimers and reduction in ADAMTS13, which correlates with blood loss, transfusion requirement, and injury severity. These findings suggest the potential for future trials targeting ADAMTS13 repletion to enhance clearance of VWF multimers.

Heparin-induced thrombocytopenia associated with collection of hematopoietic progenitor cells by apheresis.

Heparin-induced thrombocytopenia (HIT) can occur following exposure to heparin and is characterized by thrombocytopenia with increased risk for thrombosis. This condition is mediated by formation of immunoglobulin G antibodies against platelet factor 4/heparin complexes that can subsequently lead to platelet activation. Herein, we detail the clinical and laboratory findings, treatments, and outcomes of two patients who developed HIT and thrombosis after undergoing collection of hematopoietic progenitor cells by apheresis (HPC-A) for autologous HPC transplant. Given that heparin may be used during HPC-A collections, these cases emphasize the importance of prompt consideration of HIT in patients that develop thrombocytopenia and thrombosis following HPC-A collection with heparin anticoagulation.

Interval decline in hemoglobin A is associated with annual clinical event rate in sickle cell anemia patients receiving maintenance apheresis RBC exchange.

BACKGROUND: Apheresis red blood cell (RBC) exchange (RCE) is a standard intervention for patients with sickle cell anemia (SCA) who have had previous thromboembolic stroke or intractable chronic pain. Replacing sickling cells with those containing hemoglobin A (HbA) minimizes microvascular pathophysiology that produces clinical crises. Limited data exist regarding the interval changes in HbA between transfusions. We sought to describe the HbA decrement between RCE procedures and its relationship to clinical status. STUDY DESIGN AND METHODS: SCA patients (all hemoglobin SS disease) treated with maintenance RCE (n = 21) over a 15-month period at two neighboring institutions were retrospectively reviewed. Time-normalized daily HbA decrement was calculated to reflect loss of transfused RBCs, and annual events of either emergency department or hospital admissions for SCA complications were noted. Associations between HbA decrement and laboratory measures were calculated using mixed linear regression models and unpaired t test was used to compare HbA decrement between high and low event rate groups. RESULTS: A total of 31 events were recorded, and mean HbA decrement per day was 0.77 ± 0.16%. The mean interval between RCEs was 36 ± 12 days. Patients with more annual events exhibited a significantly greater daily HbA decrement (p = 0.007). No significant association between RBC unit age and HbA decrement or annual event rate was observed. CONCLUSIONS: Patients exhibiting greater daily HbA decrement were more likely to have multiple emergency department visits or admissions for sickling crises. Modulating HbA decrement may merit study as an intermediate metric for interventions to improve outcomes in hemoglobin SS disease.

Revisiting Bone Marrow Core Biopsy Adequacy Criteria in the Era of Extensive Ancillary Testing.

BACKGROUND: Bone marrow core biopsy is a routine component of comprehensive marrow evaluation, and adequacy criteria have been recommended. However, the effectiveness of these adequacy criteria for diagnostic bone marrow evaluation needs to be reassessed in the current era of extensive ancillary testing. We aimed to determine the impact of core biopsy length and intertrabecular area of evaluable bone marrow on overall adequacy for diagnostic marrow evaluation at our tertiary care institution. METHODS: Five hundred sequential cases of iliac crest bone marrow sampling were identified by retrospective re-view at our tertiary care institution. In this cohort, 470 core biopsies were obtained for histologic evaluation. Data including gross core biopsy length, number of intertrabecular 40x high power fields of evaluable marrow, and other pathologic/clinical parameters were compiled. RESULTS: The mean core biopsy length was 1.2 cm, and only 23% measured the recommended ≥ 1.5 cm. However, 96% of the core biopsies were interpretable and contributed to the comprehensive bone marrow evaluation. Notably, 100% of biopsies with ≥ 5.5 intertrabecular areas were contributory. Ancillary testing including immunophenotypic, cytogenetic, and/or molecular studies were performed in > 99% of cases. CONCLUSIONS: When histology was integrated with ancillary testing, the overall diagnosis was substantially limited in only 0.4% of cases and material deemed entirely insufficient in 0.4%. The number of intertrabecular 40x areas of evaluable marrow is a better predictor of adequacy than core biopsy length, and adequacy criteria should be revised in this era of extensive ancillary testing.

Therapeutic plasma exchange for management of heparin-induced thrombocytopenia: Results of an international practice survey.

INTRODUCTION: Anti-heparin/platelet factor 4 antibody immune complexes resulting from heparin-induced thrombocytopenia (HIT) are removed by therapeutic plasma exchange (TPE). We sought to define TPE in HIT practice patterns using an international survey. METHODS: A 31-item online survey was disseminated through the American Society for Apheresis. After institutional duplicate responses were eliminated, a descriptive analysis was performed. RESULTS: The survey was completed by 94 respondents from 78 institutions in 18 countries. Twenty-nine institutions (37%) used TPE for HIT (YES cohort) and 49 (63%) did not (NO cohort). Most NO respondents (65%) cited "no requests received" as the most common reason for not using TPE. Of the 29 YES respondents, 10 (34%) gave incomplete information and were excluded from the final analysis, leaving 19 responses. Of these, 18 (95%) treated ≤10 HIT patients over a 2-year period. The most common indications were cardiovascular surgery (CS; 63%) and HIT-associated thrombosis (HT; 26%). The typical plasma volume processed was 1.0 (63% CS and 58% HT). For CS, the typical replacement fluid was plasma (42%) and for HT, it was determined on an individual basis (32%). For CS, patients were treated with a set number of TPE procedures (37%) or laboratory/clinical response (37%). For HT, the number of TPE procedures typically depended on laboratory/clinical response (42%). CONCLUSION: In a minority of responding institutions, TPE is most commonly used in HIT to prophylactically treat patients who will undergo heparin re-exposure during CS. Prospective studies are needed to more clearly define the role of TPE in HIT.

Hemostasis testing and therapeutic plasma exchange: Results of a practice survey.

INTRODUCTION: Performing therapeutic plasma exchange (TPE) with albumin replacement decreases coagulation factor and platelet levels. No defined guidelines exist regarding laboratory testing to assess hemostasis in patients undergoing TPE. MATERIALS AND METHODS: A survey to evaluate hemostasis testing with TPE was distributed using online survey software. One response per institution was analyzed based on a hierarchical algorithm, excluding membrane filtration users, resulting in a maximum of 120 respondents per question. Descriptive analysis was performed with results reported as the number and/or frequency (%) of respondents to each question. RESULTS: The practices represented vary by institution type, number of apheresis procedures per year, and performance of TPE on children. Prior to TPE planned with albumin replacement, many respondents obtain laboratory studies for almost all patients (54.9% outpatients and 68.7% inpatients); however, some do not routinely obtain laboratory studies (9.7% outpatients and 4.4% inpatients). Hemoglobin/hematocrit, platelet count, fibrinogen, partial thromboplastin time (aPTT), and international normalized ratio (INR) are obtained prior to all TPE by 62.5%, 53.4%, 31.0%, 18.1%, and 17.7% of respondents, respectively; however, 1.0%, 8.7%, 29.0%, 38.3%, and 35.4%, respectively, do not routinely obtain these studies. Variation was observed in laboratory threshold values for action; the most common reported were hemoglobin/hematocrit <7 g/dL or 21% (31.0%), platelet count <50 × 109 /L (24.1%), fibrinogen <100 mg/dL (65.3%), aPTT >reference range and >1.5 times reference range (tied, 28.1%), and INR >1.5 (20.7%). CONCLUSIONS: Practice variation exists in hemostasis laboratory testing and threshold values for action with TPE. Further studies are needed to determine optimal hemostasis testing strategies with TPE.

ADAMTS13: origins, applications, and prospects.

ADAMTS13 is an enzyme that acts by cleaving prothrombotic von Willebrand factor (VWF) multimers from the vasculature in a highly regulated manner. In pathologic states such as thrombotic thrombocytopenic purpura (TTP) and other thrombotic microangiopathies (TMAs), VWF can bind to the endothelium and form large multimers. As the anchored VWF chains grow, they provide a greater surface area to bind circulating platelets (PLTs), generating unique thrombi that characterize TTP. This results in microvasculature thrombosis, obstruction of blood flow, and ultimately end-organ damage. Initial presentations of TTP usually occur in an acute manner, typically developing due to an autoimmune response toward, or less commonly a congenital deficiency of, ADAMTS13. Triggers for TMAs that can be associated with ADAMTS13 deficiency, including TTP, have been linked to events that place a burden on hemostatic regulation, such as major trauma and pregnancy. The treatment plan for cases of suspected TTP consists of emergent therapeutic plasma exchange that is continued on a daily basis until normalization of PLT counts. However, a subset of these patients does not respond favorably to standard therapies. These patients necessitate a better understanding of their diseases for the advancement of future therapeutic options. Given ADAMTS13's key role in the cleavage of VWF and the prevention of PLT-rich thrombi within the microvasculature, future treatments may include anti-VWF therapeutics, recombinant ADAMTS13 infusions, and ADAMTS13 expression via gene therapy.

Bortezomib for Refractory Immune-Mediated Thrombocytopenia Purpura.

The treatment of refractory immune-mediated thrombocytopenia purpura (ITP) can be challenging. This case report describes treatment of refractory ITP with bortezomib, a proteasome inhibitor. This strategy has been successful in relapsing thrombotic thrombocytopenic purpura but is a novel therapeutic approach for ITP. Further research use of proteasome inhibition in refractory ITP may be warranted.

Hemostasis management and therapeutic plasma exchange: Results of a practice survey.

BACKGROUND: Patients undergoing therapeutic plasma exchange (TPE) may present with risks for hemorrhage or thrombosis. Use of replacement fluids devoid of coagulation factors will decrease factor levels and platelet levels. There are no established guidelines for hemostasis management in these situations. MATERIALS AND METHODS: A survey to evaluate current hemostasis management practice during TPE was conducted using online survey software. One response per institution was analyzed based on a hierarchical algorithm, excluding membrane filtration users, resulting in a maximum of 107 respondents. Descriptive analysis was performed with results reported as the number and frequency (%) of respondents to each question. RESULTS: Apheresis Medicine physicians, alone (59.4%) or jointly with the requesting provider (29.2%), choose the replacement fluid. Based on a theoretical patient case receiving five TPEs approximately every other day, the percent of respondents who would use albumin with or without normal saline was 94.7% with no history of a bleeding or clotting disorder, 1.1% with active bleeding, and 8.8% with hypofibrinogenemia (<100 mg/dL) due to recent TPE. More respondents would use albumin with or without normal saline for replacement fluid when a minor invasive procedure (49.5%) vs a major surgery (8.9%) was performed 1 day before TPE. Replacement fluid selection varied among respondents for several other clinical conditions. The most frequent use for cryoprecipitate by respondents (14.3%) was hypofibrinogenemia. CONCLUSIONS: These survey results demonstrate wide interinstitutional variation in replacement fluid selection to manage hemostasis in patients undergoing TPE. Further studies are needed to guide optimal hemostasis management with TPE.

Blood product utilization in human upper-extremity transplantation: challenges, complications, considerations, and transfusion protocol conception.

BACKGROUND: Upper-extremity transplantation (UET) is a reality. Immunologic, functional, and graft survival outcomes have been encouraging. However, these complex reconstructions have unique considerations that pose distinct challenges. Transplant programs have reported morbidity and mortality due to significant intraoperative blood losses, but similar data are scant during other phases of recovery. We report experience from two centers on complete blood component demands and utilization with UET. STUDY DESIGN AND METHODS: Inpatient medical records of UET recipients from intraoperative (time from initiation of transplant surgery to exit from the operative suite) and postoperative (exit from the operative suite to discharge from the hospital) phases were retrospectively reviewed. RESULTS: Six patients received various UETs and mean (±SD) postoperative hospital stay was 46 (±14.4) days. Mean (±SD) intraoperative blood unit utilization was 14.8 (±10.2) red blood cells (RBCs), 10.5 (±11.8) plasma, 0.8 (±1.2) platelets (PLTs), and 0.3 (±0.8) cryoprecipitate units. Mean postoperative blood unit utilization was 9.3 (±10.4) RBCs, 5.3 (±6.7) plasma, 1.2 (±2.0) PLTs, and 0.7 (±1.6) cryoprecipitate units. Both intraoperative and postoperative blood utilization for unilateral versus bilateral transplant were different, but not significantly so. However, total inpatient blood use in bilateral transplants was significantly greater than in unilateral transplants. CONCLUSION: Substantial blood loss may occur in UET and require transfusion of many blood components, primarily RBCs and plasma. We propose an UET transfusion protocol and suggest that centers preparing to perform these transplants should actively engage the transfusion medicine service to ensure availability and access to appropriate blood components for the entire hospitalizations of these unique patients.

Importance of pharmacokinetic studies in the management of acquired factor X deficiency.

Up to 14% of individuals with systemic AL amyloidosis develop acquired factor X deficiency, which occurs due to adsorption of factor X onto amyloid fibrils. Although baseline factor X levels are not predictive of bleeding risk in these patients, serious hemorrhagic complications can occur, particularly during invasive procedures. Optimal management strategies to attenuate bleeding risk in these patients are unknown. We describe our experience in the management of acquired factor X deficiency, secondary to systemic AL amyloidosis, in a case series of three patients who received prothrombin complex concentrates (PCCs) for treatment and prevention of bleeding events. We performed a retrospective review extracting information on baseline demographics, laboratory data, pharmacokinetic (PK) studies, and clinically documented bleeding events. Our case series demonstrates that individuals with acquired factor X deficiency secondary to amyloidosis have variable laboratory and clinical responses to PCCs. This is likely due to distinct amyloid loads and fibril sequences, leading to different binding avidities for factor X. Our data emphasize the importance of performing PK testing prior to any invasive procedures to determine the dose and frequency interval to achieve adequate factor X levels for hemostasis, given the variable response between individuals.