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Jonathan C Roberts,1 Annette von Drygalski,2 Jenny Y Zhou,2 George M Rodgers,3 Kristin Ansteatt,1 Michael D Tarantino1 1Bleeding & Clotting Disorders Institute, University of Illinois College of Medicine – Peoria, Peoria, IL, USA; 2Hemophilia and Thrombosis Treatment Center, University of California at San Diego, San Diego, CA, USA; 3Division of Hematology and Hematologic Malignancies, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, UT, USACorrespondence: Michael D Tarantino, The Bleeding and Clotting Disorders Institute, University of Illinois College of Medicine – Peoria, 427 West Northmoor Road, Peoria, IL, 61614, USA, Tel +1 309-692-5337, Email mtarantino@ilbcdi.orgAbstract: Hereditary antithrombin deficiency (ATD) is a rare autosomal dominant condition (estimated prevalence 1:500– 1:5000). Most ATD patients have AT activity levels 40– 60% of normal. We present treatments for venous thromboembolism (VTE) in five cases of hereditary ATD. Four patients had a family history of ATD, and one had a de novo mutation. The majority of patients had a VTE while on prophylactic anticoagulation. AT concentrate augmentation was added in these cases to treat the VTE and for prophylaxis against further episodes. Two patients had significant bleeding events, one had permanent physical sequelae. Two of the patients were pregnant. VTE is a common cause of morbidity and mortality during pregnancy. Although low molecular weight heparins are the drugs of choice during pregnancy, this treatment was inadequate in one patient (developed VTE on therapy). These cases emphasize the need to screen for ATD in young patients (< 55 years) presenting with VTE. AT augmentation therapy may be necessary in patients inadequately treated with conventional anticoagulants. Careful monitoring and individualized care are needed in ATD patients, especially those with demonstrated bleeding tendencies.Keywords: clotting disorders, venous thromboembolism, anticoagulation, bleeding tendencies

Background The efficacy and safety of wilate (human von Willebrand factor/coagulation factor VIII) in patients with von Willebrand disease (VWD) has been demonstrated in clinical trials. Here, we present real-world data on the use of wilate for the routine care of patients with VWD. Objectives The objectives of this observational, prospective, phase 4 study were to evaluate the safety, tolerability, and effectiveness of wilate in on-demand treatment of bleeding episodes (BEs), long-term prophylaxis, and surgical prophylaxis among patients with any type of VWD. Methods Patients were enrolled at 31 study centers in 11 countries and followed for up to 2 years. Safety endpoints included adverse drug reactions (ADRs) and drug tolerability. Effectiveness was assessed using annualized bleeding rates (ABRs) during prophylaxis and predefined criteria for the treatment of BEs and surgical prophylaxis. Results A total of 111 patients (76 [68%] female) including 41 (37%) children were treated with wilate. Twenty-five patients received prophylaxis, 29 on-demand treatment, and 62 surgical prophylaxis. Tolerability was rated by patients as “excellent” for 96.2% of 6,497 infusions. No unexpected ADRs or thrombotic events were reported. Median ABR during prophylaxis was 1.9. Effectiveness was assessed as “excellent” or “good” by patients and investigators for 100% of BEs treated on-demand, 98% (patient rating) and 99% (investigator rating) of breakthrough BEs, and 99% of surgical procedures (investigator rating). Conclusion wilate was safe, well tolerated, and effective for the prevention and treatment of bleeding in pediatric and adult VWD patients in a real-world setting.

Iron plays an important role in mammalian physiological processes. It is a critical component for the function of many proteins, including enzymes that require heme and iron-sulfur clusters. However, excess iron is also detrimental because of its ability to catalyze the formation of reactive oxygen species. As a result, cellular and systemic iron levels are tightly regulated to prevent oxidative damage. Iron deficiency can lead to a number of pathological conditions, the most prominent being anemia. Iron deficiency should be corrected to improve adult patients’ symptoms and to facilitate normal growth during fetal development and childhood. However, inappropriate use of intravenous iron in chronic conditions, such as cancer and heart failure, in the absence of clear iron deficiency can lead to unwanted side effects. Thus, this form of therapy should be reserved for certain patients who cannot tolerate oral iron and need rapid iron replenishment. Here, we will review cellular and systemic iron homeostasis and will discuss complications of iron deficiency.

Background Acquired von Willebrand syndrome (AVWS) has been associated with monoclonal gammopathy of undetermined significance (MGUS), with limited data on its management. Methods We conducted a systematic literature search in Medline (Ovid), Embase, and Scopus up to September 11, 2019, for studies reporting on the management of AVWS associated with MGUS (AVWS‐MGUS). Data on patient characteristics, laboratory parameters at presentation, and clinical and laboratory outcomes were extracted. Objectives To describe the clinical presentation and outcomes of different therapeutic approaches. Results Seventy‐five studies were included in the final review, for a total of 137 patients. Most patients had von Willebrand factor ristocetin cofactor activity

The objectives of this study were firstly to determine the prevalence of overweight/obesity in adult persons with hemophilia in Utah, and to explore the association between age, disease severity and race with body mass index (BMI), and secondly to provide recent data on the prevalence of overweight/obesity in the hemophilia population via a review of the literature. We conducted a retrospective cross section study of adult persons with hemophilia who were seen at a Utah hemophilia treatment center from 1 January 2017 to 31 December 2019. The electronic database PubMed was searched for studies with observation periods from 1 January 2012 to 31 December 2019. The age-adjusted prevalence for overweight/obesity in the adult Utah hemophilia population was higher than the overall Utah population and the general US population. After adjusting for race and age, mild hemophilia was associated with a 7.7% higher BMI (95% confidence interval, 0.023-15.98%, P < 0.05). Review of the literature demonstrated high levels of overweight/obesity in hemophilia communities globally with considerable heterogeneity between studies. Despite increasing awareness, prevalence of overweight/obesity in the hemophilia population remains high in comparison with the general population. There is a critical need to address this issue acutely at hemophilia treatment centers due to the considerable burden of obesity.

Despite increasing use of targeted therapies to treat cancer, anemia remains a common complication of cancer therapy. Physician concerns about the safety of intravenous (IV) iron products and erythropoiesis-stimulating agents (ESAs) have resulted in many patients with cancer receiving no or suboptimal anemia therapy. In this article, we present 4 patient cases that illustrate both common and complex clinical scenarios. We first present a review of erythropoiesis and then describe our approach to cancer-associated anemia by identifying the contributing causes before selecting specific treatments. We summarize clinical trial data affirming the safety and efficacy of currently available IV iron products used to treat cancer-associated anemia and illustrate how we use commonly available laboratory tests to assess iron status during routine patient management. We compare adverse event rates associated with IV iron vs red cell transfusion and discuss using first-line IV iron monotherapy to treat anemic patients with cancer, which decreases the need for ESAs. A possible mechanism behind ESA-induced tumor progression is discussed. Finally, we review the potential of novel therapies such as ascorbic acid, prolyl hydroxylase inhibitors, activin traps, hepcidin, and bone morphogenetic protein antagonists in treating cancer-associated anemia.

e23001 Background: Anemia is an extremely common and robustly deleterious complication experienced by patients with cancer, with impacts ranging from patient-reported quality-of-life metrics, to functional capacity, to morbidity and mortality implications. Cancer-related anemia (CRA) and chemotherapy-induced anemia (CIA) arise from a complex pathogenesis and are often associated with multifactorial etiology, but iron deficiency (ID) is an especially prominent genesis in these patients and is a preeminent clinical focus for hematology/oncology clinicians, not only because of its frequency, but also because it is directly treatable and reversible. Recent positive data readouts examining intravenous iron as a mechanism to improve anemia outcomes in comorbid oncologic states illustrates a compelling and exigent need to educate the hematology/oncology clinicians managing patients with cancer. These clinicians are optimally positioned to ensure improved CRA/CIA patient outcomes. That was the formative objective of this educational initiative. Methods: We conducted a 180-minute symposium at the 2021 American Society of Hematology (ASH) Annual Meeting, with a panel of 5 hematology/oncology experts. The activity was delivered live, in-person in Atlanta, and was also live streamed to a national and international audience on a virtual basis; the session was then provided as an online on-demand offering for those couldn’t attend the live meeting. Clinician knowledge metrics were evaluated from pre-activity to post-activity via audience response software (in-person) and Zoom polling (virtual); all test questions were directly correlated with activity learning objectives. Results: Across all 3 delivery modalities, the educational initiative reached a vast audience of nearly 8,000 learners. Meaningful knowledge advancements were achieved across each of the following clinical topics of emphasis (statistics reflect differential between pre-test and post-test performance): Diagnosis of CRA/CIA using clinical signs, symptoms, and laboratory diagnoses (+17%). Differentiation of functional vs. absolute iron deficiency (+33%). Identifying how elevated hepcidin levels impact iron supplementation strategies (+37%). Knowledge of improved safety profiles of next-generation IV iron products (+75%). Correctly evaluating the benefits of IV iron given a real-world CIA patient case (+33%). Conclusions: Our outcomes illustrate both the relatively low baseline knowledge of hematology/oncology clinicians related to CRA/CIA management and the transformative impact of timely educational programming. Ongoing educational efforts focused on this clinical topic and target audience are warranted.

Normal hemostasis provides for balanced interactions between the blood vessel wall, coagulation proteins, and platelets. After vascular injury, primary hemostasis and secondary hemostasis function in a coordinated fashion to stop bleeding. Standard coagulation tests have been shown in multiple studies to predict bleeding and mortality in neurosurgical patients. Emerging coagulation tests are useful point-of-care assays that guide transfusion therapy and diagnose patients with hyperfibrinolysis. This article provides an overview of hemostasis, a summary of standard coagulation testing and point-of-care tests, and a brief review of coagulation test usefulness in neurosurgery, focusing on studies in patients with traumatic brain injury.

Romiplostim is a thrombopoietin receptor agonist approved for the treatment of immune thrombocytopenia purpura. When following FDA-approved romiplostim prescribing recommendations to withhold treatment for platelet counts above 400k/µL, some patients exhibit a precipitous decline in their platelet count potentially causing patient harm. We present two cases where stable platelet counts were achieved only through persistent weekly dosing of romiplostim despite platelet counts above 400k/µL on the day of administration. Therefore, continuous weekly dosing of romiplostim despite platelet count being above 400k/µL combined with twice weekly vigilant monitoring is an alternative method of romiplostim dosing that mitigates severe fluctuations in platelets. We also discuss important details, postulated mechanisms, and evidence-based mitigation strategies.

ADAMTS-13, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13, is a zinc-containing metalloprotease that cleaves von Willebrand factor (vWf). Previous publications by our laboratory have shown that ADAMTS-13 may also be involved in angiogenesis. For this study, we report the successful transient knockdown of endogenous ADAMTS-13 in human umbilical vein endothelial cells (HUVEC) via siRNA and the effects of reduced endogenous ADAMTS-13 on HUVEC angiogenesis functions. 15nM of ADAMTS-13 siRNA reduced HUVEC ADAMTS-13 protein levels by 90% after 24h incubation, whereas control siRNA did not affect endogenous ADAMTS-13 levels. Furthermore, this transfection did not affect the HUVEC endogenous protein level of ADAMTS-1, a related family member of ADAMTS-13 indicating the specificity of the siRNA. Transfection of HUVEC with 15nM of ADAMTS-13 siRNA resulted in a 21% decrease in proliferation after 24h incubation. The effects of ADAMTS-13 knockdown on migration of HUVEC across a scratch wound were also evaluated. 24h after transfection with control siRNA, there was increased cell migration across the scratch wound. This dramatic migration did not occur with ADAMTS-13 knockdown cells. Decreased protein levels of endogenous ADAMTS-13 also affected angiogenesis as measured by endothelial cell tube formation using a Matrigel matrix method. The tube lengths, sizes and junction numbers of the ADAMTS-13 knockdown cells were all significantly lower compared to control cells by about 40%. The protein level of vascular endothelial growth factor (VEGF), a well-known regulator of angiogenesis, was significantly decreased by 45% upon knockdown of ADAMTS-13. Moreover, activity of the AKT pathway, one of the VEGF angiogenesis downstream signaling pathways was down-regulated by ADAMTS-13 siRNA. These data indicate that in cultured endothelial cells, one role of endogenous ADAMTS-13 is regulation of angiogenesis, mediated through VEGF and AKT signaling pathway. Overall, our data suggest an additional model of endogenous ADAMTS-13 functionality, beyond that of cleaving von Willebrand factor.

D-dimer is an indirect marker of fibrinolysis and fibrin turnover; this molecule exhibits unique properties as a biological marker of hemostatic abnormalities as well as an indicator of intravascular thrombosis. D-dimer is a soluble fibrin degradation product that results from the systematic degradation of vascular thrombi through the fibrinolytic mechanism. Because of this, the D-dimer serves as a valuable marker of activation of coagulation and fibrinolysis in a number of clinical scenarios. Most commonly, D-dimer has been extensively investigated for excluding the diagnosis of venous thromboembolism (VTE) and is used routinely for this indication. In addition, D-dimer has been evaluated for determining the optimal duration of anticoagulation in VTE patients, for diagnosing and monitoring disseminated intravascular coagulation, and for monitoring other conditions in which the patient is at high risk of bleeding or thrombosis. Limitations of the assay include D-dimer elevation in a constellation of clinical scenarios (age, pregnancy, and cancer) and lack of clinical standardization.

Purpose To identify the molecular cause in five unrelated families with a distinct autosomal dominant ocular systemic disorder we called ROSAH syndrome due to clinical features of retinal dystrophy, optic nerve edema, splenomegaly, anhidrosis, and migraine headache. Methods Independent discovery exome and genome sequencing in families 1, 2, and 3, and confirmation in families 4 and 5. Expression of wild-type messenger RNA and protein in human and mouse tissues and cell lines. Ciliary assays in fibroblasts from affected and unaffected family members. Results We found the heterozygous missense variant in the ɑ-kinase gene, ALPK1, (c.710C>T, [p.Thr237Met]), segregated with disease in all five families. All patients shared the ROSAH phenotype with additional low-grade ocular inflammation, pancytopenia, recurrent infections, and mild renal impairment in some. ALPK1 was notably expressed in retina, retinal pigment epithelium, and optic nerve, with immunofluorescence indicating localization to the basal body of the connecting cilium of the photoreceptors, and presence in the sweat glands. Immunocytofluorescence revealed expression at the centrioles and spindle poles during metaphase, and at the base of the primary cilium. Affected family member fibroblasts demonstrated defective ciliogenesis. Conclusion Heterozygosity for ALPK1, p.Thr237Met leads to ROSAH syndrome, an autosomal dominant ocular systemic disorder.

The authors investigated Daikyo CZ cyclic olefin polymer for storing a labile protein-ADAMTS13 and culturing adherent mammalian cells. ADAMTS13 was stored in different containers for one and four months. Protein recovery assays suggest that ADAMTS13 remained enzymatically active. ADAMTS13 recovered from CZ containers is comparable to that of polypropylene vials, and is 10% greater than glass vials. LN229 and HUVEC cells were cultured in CZ containers. Cell proliferation, viability, and migration were studied. LN229 cells cultured in CZ containers exhibited 36% higher proliferation rate and an increase in cell migration, as compared to the polystyrene containers. HUVEC proliferated slower in CZ containers.

INTRODUCTION Evaluation of von Willebrand factor (VWF) multimeric distribution is useful for subclassification of von Willebrand disease (VWD). Multimer analysis has historically been a manual, labor-intensive laboratory-developed test. The first commercial method for multimeric analysis was recently developed that utilizes a single instrument for gel electrophoresis, staining, and densitometry. The current study was undertaken to evaluate the performance characteristics of the new commercial method. METHODS Studies performed with the commercial method included evaluation of accuracy (method comparison), reference intervals (establishment of normal migration patterns in normal donor specimens), precision (multimer pattern reproducibility), and analytical sensitivity. RESULTS In the method comparison studies, concordant interpretations were obtained in 19 of 24 comparisons, including normal and abnormal specimens. The 5 specimens with discordant interpretations all involved slight differences and none were considered clinically significant. Thirty-eight normal donor specimens demonstrated normal multimer patterns. Multimer pattern reproducibility was demonstrated in normal and abnormal controls tested on each gel. In the sensitivity studies, adequate visualization of multimers was determined to require VWF protein concentrations of approximately 5%-10% of normal. CONCLUSION The commercial multimer method is a streamlined test that demonstrates comparable performance characteristics to our current laboratory-developed method and that provides the advantage of both electrophoresis gels and densitometry scans to aid interpretation.

We demonstrate that SCF-KIT signaling induces synthesis and secretion of endothelin-3 (ET3) in human umbilical vein endothelial cells and melanoma cells in vitro, gastrointestinal stromal tumors, human sun-exposed skin, and myenteric plexus of human colon post-fasting in vivo. This is the first report of a physiological mechanism of ET3 induction. Integrating our finding with supporting data from literature leads us to discover a previously unreported pathway of nitric oxide (NO) generation derived from physiological endothelial NO synthase (eNOS) or neuronal NOS (nNOS) activation (referred to as the KIT-ET3-NO pathway). It involves: (1) SCF-expressing cells communicate with neighboring KIT-expressing cells directly or indirectly (cleaved soluble SCF). (2) SCF-KIT signaling induces timely local ET3 synthesis and secretion. (3) ET3 binds to ETBR on both sides of intercellular space. (4) ET3-binding-initiated-ETBR activation increases cytosolic Ca2+, activates cell-specific eNOS or nNOS. (5) Temporally- and spatially-precise NO generation. NO diffuses into neighboring cells, thus acts in both SCF- and KIT-expressing cells. (6) NO modulates diverse cell-specific functions by NO/cGMP pathway, controlling transcriptional factors, or other mechanisms. We demonstrate the critical physiological role of the KIT-ET3-NO pathway in fulfilling high demand (exceeding basal level) of endothelium-dependent NO generation for coping with atherosclerosis, pregnancy, and aging. The KIT-ET3-NO pathway most likely also play critical roles in other cell functions that involve dual requirement of SCF-KIT signaling and NO. New strategies (e.g. enhancing the KIT-ET3-NO pathway) to harness the benefit of endogenous eNOS and nNOS activation and precise NO generation for correcting pathophysiology and restoring functions warrant investigation.

Cancer-related anemia (CRA) is due to multiple etiologies, including chemotherapy-induced myelosuppression, blood loss, functional iron deficiency, erythropoietin deficiency due to renal disease, marrow involvement with tumor as well as other factors. The most common treatment options for CRA include iron therapy, erythropoietic-stimulating agents (ESAs), and red cell transfusion. Safety concerns as well as restrictions and reimbursement issues surrounding ESA therapy for CRA have resulted in suboptimal treatment. Similarly, many clinicians are not familiar or comfortable using intravenous iron products to treat functional iron deficiency associated with CRA. This article summarizes our approach to treating CRA and discusses commonly encountered clinical scenarios for which current clinical guidelines do not apply.

Background: Von Willebrand disease (VWD) is the most common inherited bleeding disorder, affecting 1% of the population, and characterized by deficient or defective von Willebrand factor (VWF). Among women with VWD, up to 80% have heavy menstrual bleeding (HMB), many of whom have depleted iron stores and iron deficiency anemia with reduced physical functioning, anxiety, depression, and poor quality of life. HMB is a serious problem causing significant health burden for those affected. The lack of effective therapies for menorrhagia is a major unmet healthcare need in women with VWD: in up to 30% desmopressin (DDAVP), combined oral contraceptives (COCs) hormones, or the recommended non-hormonal agent, tranexamic acid (Lysteda®, TA) may be ineffective or poorly tolerated. VWF concentrates, including plasma-derived VWF (pdVWF, Humate-P®) and recombinant VWF (rVWF, Vonvendi®) safely reduce bleeds in VWD, but few data exist on VWF use in menorrhagia, and no prospective trials are available to guide treatment. As rVWF has higher purity, potency, and a longer half-life than pdVWF, this phase III trial will compare rVWF with TA in reducing menorrhagia in women with type 1 VWD. Methods: This is an NHLBI-funded U01 phase III multicenter, prospective, randomized, crossover trial in to compare IV rVWF vs. po TA in reducing menorrhagia in type 1 VWD, clinicaltrials.gov, NCT02606045. Women with type 1 VWD, VWF:RCo100 in at least one of the last two cycles, are eligible. Exclusions include hypothyroidism, past thrombosis, and renal disease. Subjects are randomized to rVWF 40 IU/kg IV day 1 vs. TA 1300 mg po three times daily days 1-5 in each of two consecutive cycles. The order of treatment is determined by randomization: in Group 1, rVWF is given in cycles 1 and 2, and TA in cycles 3 and 4; while in Group 2, TA is given in cycles 1 and 2, and rVWF in cycles 3 and 4. A rescue dose day of rVWF 40 IU/kg may be given day 2 of cycles in which rVWF is given. The primary endpoint is a 40-point reduction in PBAC, a validated measure of menstrual loss, after 2 cycles. As rVWF is a greater burden (IV, cost), to show it is superior to TA, it should improve PBAC 40 points more from baseline than TA. Secondary endpoints are cycle severity, cycle length, QoL (SF-36, Ruta, CDC-HRQ0L-14, CES-D), and satisfaction survey. Treatment response will also be compared with VWF assays and VWF genotype. Safety is assessed by number of rescue doses, other bleeding, thrombosis, and allergic reaction. Our research hypothesis is that rVWF will be superior, producing a greater improvement, by at least 40 points, in PBAC, than TA. We also hypothesize that rVWF will be as safe, tolerable, and acceptable as TA, and that VWF assays and VWF genotype will predict response to treatment. A sample size of 60 (inflated to 66 for 5% attrition) will provide 84% power to detect a difference in improvement of 40 points between rVWF and TA. Analysis will be by intent-to-treat analyses, with a two-tailed alternative hypothesis with type 1 error rate of 0.05, a 4-period 2-group (AABB/BBAA) crossover design, and an estimated between-subject standard deviation (SD) of 63 points and within subject SD of 100 points. Results: A total of 442 potential subjects have been identified at 19 participating HTCs, of whom 33 (7.5%) are eligible, and 2 enrolled. The most common reason for ineligibility is use of an IUD (15.6%), COCs (9.4%), age Discussion: In conclusion, rVWF is a high-purity VWF concentrate with a longer half-life than pdVWF. In this multicenter phase III trial, rVWF is being compared to the current non-hormonal standard, TA, to reduce menorrhagia in adult women with type 1 VWD. rVWF is safe and effective in prevention and treatment of bleeds, and this trial will determine if rVWF reduces menorrhagia to a degree sufficient to justify its IV route and cost. Disclosures Ragni: Sangamo: Research Funding; Alnylam/Sanofi: Consultancy, Research Funding; ICER: Consultancy; OPKO: Research Funding; Bioverativ/Sanofi: Consultancy, Research Funding; Bayer: Consultancy; Biomarin: Consultancy, Research Funding; Shire/Takeda: Consultancy, Other: Study drug; Spark Therapeutics: Consultancy, Research Funding. Seaman:Spark Therapeutics: Consultancy; Genentech: Consultancy; Bayer: Consultancy; Takeda: Consultancy. Sidonio:Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Genetech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda-Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bioverativ: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: Membership on an entity's Board of Directors or advisory committees, Research Funding; Uniqure: Membership on an entity's Board of Directors or advisory committees; Kedrion: Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Biomarin: Membership on an entity's Board of Directors or advisory committees. Kuriakose:Alexion: Consultancy, Honoraria, Speakers Bureau; Bayer: Consultancy. Malec:Hemostasis and Thrombosis Research Society: Membership on an entity's Board of Directors or advisory committees; Spark: Honoraria; Sanofi: Consultancy, Honoraria, Speakers Bureau; Bayer: Honoraria; CSL: Honoraria. Rodgers:AstraZeneca: Consultancy; Sanofi: Consultancy; Novartis: Consultancy; Octapharma: Consultancy; Pfizer: Consultancy. Wheeler:Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novo Nordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees; Octapharma: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Introduction: Clotting factor replacement therapy in the management of persons with hemophilia A (PwHA) is typically dosed using the following weight-based formula: Factor VIII (FVIII) Dose = Body weight (BW) in kg X desired FVIII increase (%) 2 This equation is based upon a FVIII in vivo recovery (IVR) of 2, which assumes that each FVIII unit per kg of BW infused will increase the circulating FVIII concentration by 2%. There have been a few studies demonstrating that IVR increases with increasing BW. A pharmacokinetic study performed using recombinant FVIII concentrate for pediatric PwHA 29.6 kg/m2, each group had a significantly different and increasing IVR of 1.60, 2.14 and 2.70, respectively [Henrard S, et al. Haematologica 2013; 98: 1481-6]. As there are no guidelines for dosing of factor replacement therapy for obese PwHA, these studies suggest that ideal body weight (IBW) could be considered instead of actual body weight (ABW) in the dose calculations. With the prevalence of obesity in the hemophilia population now approaching that of the general population, dosing using IBW has potential economic ramifications [Wong TE, et al. Am J Prev Med 2011; 41: S369-75, Majumdar S, et al. Haemophilia 2011; 17: 717-8]. Objectives: 1) To estimate the prevalence of overweight and obese adult persons with hemophilia (PwH) in the state of Utah; 2) To estimate the cost savings for annual prophylactic clotting factor prescriptions if they were to be written using IBW vs. ABW for adult PwHA that are obese in the state of Utah. Methods: Adult PwH (≥18 years of age) who have been seen at least once in the past 3 years (January 1, 2016 to December 31, 2018) were identified from the Utah Center for Bleeding & Clotting Disorders Registry. The following information was collected: Demographics; type of hemophilia; severity of hemophilia; height; weight; BMI. If BMI was not available, this was calculated based on the following equation, BMI = kilograms/meters2. Overweight was defined as a BMI 25 - 29.9 kg/m2. Obese was defined as a BMI ≥ 30 kg/m2. As there is limited data on the relationship between increasing BMI and IVR for factor IX concentrates, persons with hemophilia B were excluded in our cost savings analysis. For PwHA on clotting factor prophylaxis who were obese, the IBW was calculated using their height and the following equation for men: IBW (in kg) = 50 + 2.3 kg per each inch over 5 feet Using the prophylaxis schedule for each obese PwHA, an estimate of the annual cost was calculated using Wholesale Acquisition Cost and compared using both ABW and IBW. Results: A total of 87 adult PwH were seen with documented measurements of height and weight within the past 3 years. The patient characteristics are presented in Table 1. The mean and median age was 37.1 and 34 years, respectively (range: 19 - 75 years). The mean value for BMI was 28.1 and the median was 27.2 (range 17.3 - 46.0). Two patients had class III obesity (BMI ≥40 kg/m2). Almost two-thirds of adult PwH were overweight or obese (58/87; 65.5%). The prevalence of overweight and obese adult PwH in Utah based on age and severity of disease is shown in Figure 1. The estimated annual cost for each of the 12 adult obese PwHA based on their ABW vs IBW is shown in Figure 2. The difference in the total annual cost of treatment for the 12 adult PwHA on prophylaxis factor replacement therapy would be reduced by a total of roughly $2,100,000 if IBW was used rather than ABW; an average savings of $175,000 per adult PwHA per year. Conclusion: The relatively high prevalence of overweight and obesity in the Utah hemophilic population is similar to what has been reported in other states across the United States. The use of IBW in dose calculations has significant economic ramifıcations. Further studies performing individualized pharmacokinetic analysis for PwHA using IBW dosing must be coupled with close clinical monitoring to ensure safety of this dosing strategy before it can be adopted into routine clinical practice. Disclosures Rodgers: Pfizer: Consultancy; Octapharma: Consultancy; Novartis: Consultancy; Sanofi: Consultancy; AstraZeneca: Consultancy.

Objectives: Elevations of factor IX (FIX) are thought to contribute to thrombotic risk, but this has not been well characterized. We retrospectively sought to determine whether elevated FIX levels are a risk factor for thrombosis in 81 adult subjects younger than 65 years (mean, 47 years) who were referred for evaluation of a hypercoagulable state. Methods: Patients were classified by arterial transient ischemic attack/stroke (TIA/stroke, n = 62) or venous thromboembolism (VTE, n = 19) events. FIX activity testing was performed on all 81 subjects and a reference group of 40 healthy individuals. Results: Thirteen (21%) of 62 subjects with TIA/stroke and 5 (26%) of 19 subjects with VTE had elevated FIX activity. Odds ratios for TIA/stroke and VTE in subjects with elevated FIX activity were 3.7 (95% confidence interval [CI], 0.76–17.65) and 6.8 (95% CI, 1.18–39.07), respectively. Conclusions: Our findings suggest an association between elevated FIX levels and both arterial and venous thrombotic events.

Acquired haemophilia A (AHA) is a potentially life-threatening bleeding disorder occurring in patients without a previous personal or family history of bleeding. Development of immune-mediated autoantibodies against coagulation factor VIII is associated with a wide range of clinical disorders including pregnancy, autoimmune disorders, malignancy, or with no apparent disease. There exists great potential for morbidity and mortality related to acute and recurrent bleeding episodes, making prompt diagnosis and treatment necessary. The two primary goals of treatment focus on cessation of bleeding and eradication of the acquired factor VIII inhibitor. No randomized clinical trials have been conducted regarding treatment, so expert clinical opinion guides therapeutic intervention. This current report provides a profile of patient characteristics, an algorithm for diagnosis, and outlines treatment recommendations based upon current guidelines and clinical experience. As first-line interventions for acute bleeding and inhibitor eradication are generally accepted, we will emphasize discussion of second-line therapeutic options.

Background Portal vein thrombosis (PVT) is a serious problem with a high morbidity and mortality, often exceeding 40% of affected patients. Recently, PVT has been reported in patients after laparoscopic sleeve gastrectomy (LSG). The frequency is surprisingly high compared with other abdominal operations. Objective We present a series of 5 patients with PVT after LSG. The treatment was not restricted simply to anticoagulation alone, but was determined by the extent of disease. A distinction is made among nonocclusive, high-grade nonocclusive, and occlusive PVT. We present evidence that systemic anticoagulation is insufficient in occlusive thrombosis and may also be insufficient in high-grade nonocclusive disease. Setting Single private institution, United States. Methods We present a retrospective analysis of 646 patients who underwent LSG between 2012 and 2015. In all patients, the diagnosis was established with an abdominal computed tomography (CT) scan as well as duplex ultrasound of the portal venous system. All patients received systemic anticoagulation. Depending on the extent of disease, thrombolytic therapy and portal vein thrombectomy were utilized. All patients received long-term anticoagulation. Results Four patients with PVT were identified. A fifth patient with PVT after LSG was referred from another center. The mean age of all patients was 49 years. One patient had a history of deep vein thrombosis (DVT). No complications were identified intraoperatively or during the hospital stay, and all patients were discharged by postoperative day 2. The patients presented with PVT at an average of 20 days (range: 10–35) post-LSG. The CT scan was positive for PVT in all patients. In stable noncirrhotic patients with nonocclusive disease, we administered therapeutic anticoagulation. One patient with high-grade, nonocclusive PVT received anticoagulation alone. Patients with occlusive disease were treated with operative thrombectomy including intraoperative and postoperative thrombolysis (tissue plasminogen activator) with subsequent therapeutic anticoagulation, followed by oral warfarin or a factor Xa inhibitor. There was 1 death from multisystem organ failure in the patient who was referred from another institution with occlusive disease, initially managed only with an anticoagulation infusion. Conclusions We maintain that portal vein patency is essential to normal gastrointestinal physiology and should be the treatment goal in all patients with PVT. In these patients, the therapeutic option should be guided by the extent of the thrombosis. In view of currently available approaches, we propose that operative portal vein thrombectomy, in conjunction with fibrinolysis and anticoagulation, offers the best long-term success in patients with occlusive PVT.

We describe a novel inherited disorder consisting of idiopathic massive splenomegaly, cytopenias, anhidrosis, chronic optic nerve edema, and vision loss. This disorder involves three affected patients in a single non-consanguineous Caucasian family, a mother and two daughters, who are half-sisters. All three patients have had splenectomies; histopathology revealed congestion of the red pulp, but otherwise no abnormalities. Electron microscopic studies of splenic tissue showed no evidence for a storage disorder or other ultrastructural abnormality. Two of the three patients had bone marrow examinations that were non-diagnostic. All three patients developed progressive vision loss such that the two oldest patients are now blind, possibly due to a cone-rod dystrophy. Characteristics of vision loss in this family include early chronic optic nerve edema, and progressive vision loss, particularly central and color vision. Despite numerous medical and ophthalmic evaluations, no diagnosis has been discovered.

Introduction: Post-marketing studies provide important insight into the consistency of data from clinical studies and routine clinical use. This non-interventional, prospective, multicentre study (WIL-20) collected real-life data on the use of a human VWF/FVIII concentrate with the native VWF/FVIII complex in a physiological 1:1 ratio (wilate®; pdVWF/FVIII) in routine clinical practice. Here, we report the final results from this study. Methods: The primary objective was to document the safety and tolerability of pdVWF/FVIII in routine clinical practice, with a planned observation period per patient of 2 years. Secondary objectives were to document the efficacy in on-demand treatment of acute bleeding, long-term prophylaxis, and surgical prophylaxis. Male and female patients of any age and with any type of VWD who were prescribed pdVWF/FVIII were eligible for the study. pdVWF/FVIII was administered at the investigator's discretion. Data recorded included patient demographics, laboratory parameters, treatment details, and occurrence of adverse drug reactions (ADRs), including immunogenicity and thrombogenicity. Tolerability was assessed using a verbal rating scale; efficacy of on-demand treatment and surgical prophylaxis using a haemostatic scale; and prophylactic efficacy based on the frequency of spontaneous breakthrough bleeds. Results: The study enrolled 120 patients from 11 countries. Within the safety population (111 patients who received at least one dose of pdVWF/FVIII), 45% of patients had type 1 VWD, 29% type 2 and 18% type 3; disease type was unavailable for 8 patients, and 1 patient was diagnosed with haemophilia A during the study. Of the 111 patients, 33% were previously untreated with a FVIII/VWF product. A total of 7024 infusions were administered to the safety population over a median observation time of 2 years; median dose was 320.5 IU/kg. A total of 26 ADRs were reported in 8 patients; 4 were mild, 3 moderate and 1 severe. Three patients discontinued treatment and 1 stopped treatment temporarily due to adverse events. Using an experimental assay, 3 cases of VWF inhibitors were identified, with no impact on clinical outcome. No thromboembolic events were reported. Tolerability was rated for 6497 infusions, with 96.2% rated 'excellent', 3.7% 'satisfactory', and 0.1% 'unsatisfactory'. Of the 29 patients treated on-demand, 150 bleeding events (BEs), excluding menstrual bleeds, were reported in 25 patients; 18% of BEs were mild, 71.3% were moderate, and 10% were severe. 94% of treated bleeds (130/138) resolved with 1 or 2 infusions, with a median dose per BE of 33 IU/kg. The efficacy of treatment was rated as 'excellent' or 'good' for 100% of BEs. Of the 25 patients treated with pdVWF/FVIII for prophylaxis, 18 patients had a total of 233 breakthrough BEs; 37% mild, 44% moderate, and 9% severe (severity information was unavailable for 11% of bleeds). Of the breakthrough BEs that required treatment, 85% (149/175) were treated with 1 or 2 infusions of pdVWF/FVIII, with a median dose per BE of 55.4 IU/kg. Efficacy of pdVWF/FVIII was rated as 'excellent' or 'good' by investigators for 99% of 139 evaluable breakthrough BEs. For patients on prophylaxis (n = 25), the median annualised bleeding rate for spontaneous BEs was 1.5 (range 0.0-19.7). The efficacy of prophylaxis for prevention of spontaneous breakthrough bleeds was rated as 'excellent' or 'good' in 96% (24/25) of these patients. A total of 99 surgical procedures were performed in 62 patients; 56% with type 1 VWD, 29% type 2 and 13% type 3 (2% were type unknown). Of the procedures, 46 were major and 53 minor. All but one of the surgeries were managed with pdVWF/FVIII prophylaxis, and the efficacy was rated as 'excellent' or 'good' in 99% (96/97) of surgeries with assessments available. Conclusions: The final results of this non-interventional study indicate that pdVWF/FVIII is well tolerated and effective for on-demand treatment, prophylaxis, and surgical prophylaxis in patients with all types of VWD treated as part of routine clinical practice. The data are consistent with those from previous clinical studies and provide real-life evidence from around the world on the use of pdVWF/FVIIIfor management of VWD in all clinical settings. Disclosures Werner: Octapharma USA Inc.: Employment. Hashimoto:Octapharma USA Inc.: Employment. Knaub:Octapharma AG: Employment. Rodgers:Octapharma: Membership on an entity's Board of Directors or advisory committees, Research Funding.

For a majority of patients with venous thromboembolism (VTE), initial treatment is straightforward and necessitates the immediate initiation of a parenteral anticoagulant (eg, heparin or low molecular weight heparin), simultaneous initiation of long-term therapy (eg, vitamin K antagonist), and discontinuation of the parenteral anticoagulant after 5 days assuming that the vitamin K antagonist is therapeutic. This standardized approach is based on numerous pivotal clinical trials completed over the past 3 decades. Yet, advances in standardized VTE treatment continue to evolve and include issues related to the selection and dosing of parenteral anticoagulants (eg, relative efficacy and dosing in the obese patient, patients with renal impairment, and pregnant patients), optimal location of initial care delivery, use of dosing initiation nomograms for vitamin K antagonists with the potential of gene-based dosing, and demonstration that longterm low molecular weight heparin therapy may be optimal for some patient populations (eg, those with active cancer). Further, in parallel with the evolution of VTE treatment, there have been remarkable advances in our understanding of heparin-induced thrombocytopenia, a prothrombotic complication of parenteral anticoagulant use.

ADAMTS-13, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13, is a zinc-containing metalloprotease that cleaves von Willebrand factor. Previous publications by our laboratory have shown that either endogenous or exogenous ADAMTS-13 may regulate angiogenesis in endothelial cells; for example, siRNA knockdown of endogenous endothelial cell ADAMTS-13 reduced angiogenic activities including cell migration, proliferation, and tube formation (Tang et al. Microvascular Res 2017; 113:85-70). Many tumor cells have the ability to develop a vascular phenotype, a process known as vasculogenic mimicry (VM). There is a multitude of evidence demonstrating that tumor cell-mediated VM may play a vital role in tumor development, independent of endothelial cell angiogenesis. For this study, we report that decreasing ADAMTS-13 levels inhibit vasculogenic functions in a glioblastoma cell line (LN-229), while increasing ADAMTS-13 levels had no effect. Incubating up to 30ng/ml of exogenous ADAMTS-13 did not promote cell proliferation and up to 200ng/ml did not change tube formation in LN-299 brain tumor cells. One possible explanation for this observation is that LN-299 brain tumor cells have almost twice the endogenous ADAMTS-13 expression than endothelial cells (~200pg/ml vs ~100pg/ml), so this cell line is not sensitive to exogenous ADAMTS-13. Using siRNA, we were able to successfully knockdown endogenous ADAMTS-13 in human brain tumor LN-229 cells. 50nM of ADAMTS-13 siRNA in a six-well plate inhibited HUVEC ADAMTS-13 expression levels by 75% after 48hr incubation, whereas control siRNA did not affect endogenous ADAMTS-13 levels. Additionally, expression of ADAMTS-1, a related family member of ADAMTS-13 was not affected by the knockdown. The effects of reduced endogenous ADAMTS-13 on glioblastoma vasculogenic functions were studied. Transfection of HUVEC with 50nM of ADAMTS-13 siRNA in a 24-well plate resulted in about 20% decrease in proliferation after 24hr and 48hr incubation. We demonstrated that decreased expression of endogenous ADAMTS-13 also affected vasculogenic mimicry as measured by glioblastoma cell tube formation using a Matrigel matrix method. The tube lengths, sizes and junction numbers of the ADAMTS-13 knockdown cells were all significantly lower compared to control cells by about 30-40%, respectively. Moreover, the expression of VEGF, a well-known regulator of angiogenesis, was significantly decreased by 25% after knockdown of endogenous LN-229 ADAMTS-13. Overall, these data suggest that endogenous ADAMTS-13 may regulate glioblastoma cell growth and function. Citation Format: Huiyuan Tang, Manfai Lee, Eun Ho Kim, Daniel Bishop, George M. Rodgers. Endogenous ADAMTS-13 regulates vasculogenic functions in glioblastoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 81.

Discard tubes have traditionally been obtained when drawing samples for coagulation testing to avoid potential tissue factor activation of coagulation in the first tube that may lead to inaccurate results. Although discard tubes are no longer required for prothrombin time and partial thromboplastin time, the practice is still recommended for other coagulation studies due to lack of sufficient evidence that discard tubes are not needed. The objective of the present study was to determine whether the first citrate tube drawn can be used for special coagulation testing. We performed testing for fibrinogen, D-dimer, factors VIII, IX, XI, proteins C and S, and antithrombin on 30 healthy individuals and factors II, VII, IX, X, and proteins C and S on a second group of 30 healthy individuals and 30 individuals receiving warfarin. Testing was performed on two consecutive samples to evaluate the level of agreement between the two tubes. Paired t-testing showed no statistically significant differences between tube 1 and tube 2 for any of the tests performed. Most data pairs (tube 1, tube 2) agreed within 10% difference or less, and no positive or negative biases were observed. To our knowledge, this study is the first to evaluate the need for discard tubes in a variety of coagulation tests using both normal and abnormal samples. Our data suggest that discard tubes are not necessary when drawing samples for specialized coagulation testing.

BACKGROUND: Idiopathic thrombotic thrombocytopenic purpura (TTP) is a rare form of thrombotic microangiopathy (TMA) characterized by extreme deficiency of ADAMTS13, an enzyme responsible for cleavage of von Willebrand factor. Plasma exchange therapy is the cornerstone of current treatment and is ineffective for most other forms of TMA. The availability of ADAMTS13 testing has improved diagnostic accuracy and appropriate selection of patients who are most likely to respond to plasma exchange. STUDY DESIGN AND METHODS: We performed a retrospective chart review of 110 cases of clinically suspected TTP with ADAMTS13 test results from 2005 to the present. The primary goal was to identify presenting clinical and/or laboratory features of patients with ADAMTS13 deficiency that would prove useful in increasing the likelihood of, or excluding the possibility of, TTP. In addition, patient outcomes including alternative diagnoses and response to plasma exchange were reviewed. RESULTS: Significant correlations for severe ADAMTS13 deficiency were seen for four of the observed variables: indirect bilirubin, reticulocyte percentage, creatinine, and platelet count; a fifth variable, D-dimer, just missed significance but performed well in subsequent analysis. Receiver operator characteristics curves for individual variables had area under the curve (AUC) values ranging from 0.75 to 0.85; a combined model had an AUC of 0.98. In addition, we constructed tree models both for clinical use as a diagnostic algorithm and for recursive partitioning to help establish cutoff points for categorical variables in developing an easy-to-use clinical prediction score. CONCLUSION: These results may enable the rapid exclusion and accurate diagnosis of TTP using readily available laboratory data.

Background: The majority of venous thromboembolic events occur in hospitalized patients. Although there are several effective regimens, venous thromboembolism (VTE) prophylaxis is still under-utilized in medically-ill patients. In 2003 a multi-faceted quality improvement intervention was implemented to improve the use of VTE prophylaxis. We pre- viously described the significant improvements in VTE prophylaxis in the two years following this intervention. Objective: To determine the longitudinal effects of this quality improvement intervention in prescribing practices for VTE prophylaxis in medically-ill patients. Methods: Since the original intervention in 2002, the only on-going maintenance has been 4 annual lectures. We collected data on 121 medically-ill patients hospitalized in 2006, including risk factors for VTE, pharmacologic agent and dose pre- scribed (or mechanical devices, if uses), and timing of prophylaxis in relation to admission. Results: Overall, 83% were at high-risk for VTE and 77% received prophylaxis, a significant improvement compared to the 2002 pre-intervention cohort (40%, p

Background: ADAMTS13 is the enzyme responsible for cleaving ultra-large von Willebrand factor (vFW) multimers. Commercial kits have been recently developed that use a fluorescence resonance energy transfer (FRET) methodology to measure ADAMTS13 activity. Methods: In this study, we compared the results from 2 recently released commercial kits (GTI and Technoclone) with results obtained from a reference laboratory also using FRET technology to assay samples from patients referred for a possible diagnosis of thrombotic thrombocytopenic purpura (TTP). Results: A total of 29 samples were assayed and compared. Six samples had less than 5% of normal ADAMTS13 activity identified by the reference laboratory. The GTI kit identified only 4 of these 6 samples, while the Technoclone kit identified all 6. Conclusion: The results of this study demonstrate that commercial ADAMTS13 activity assays currently available are clinically useful in diagnosing TTP.

SummaryAntithrombin (AT) functions as a potent natural anticoagulant and serine protease inhibitor that inactivates many enzymes in the coagulation cascade. Antithrombin also possesses anti-inflammatory properties, many of which are mediated by its actions as an anticoagulant. Hereditary AT deficiency is a rare, underrecognised medical condition that is associated with inadequate endogenous anticoagulation thought to result from impaired inhibition of serine protease coagulation factors. Inherited as an autosomal dominant trait, congenital AT deficiency typically reduces functional AT levels to 40–60% of normal. As a result, individuals with hereditary AT deficiency have a ≥50% lifetime risk of venous thromboembolism (VTE). Specifically, AT deficiency is associated with a three- to seven-fold higher risk of VTE compared with other thrombophilias. Thus, maintaining adequate levels of AT during high-risk periods is an important treatment goal. Long-term anticoagulant thromboprophylaxis is not recommended in asymptomatic patients with AT deficiency because of the increased risk of haemorrhage. However, treatment guidelines recommend short-term thromboprophylaxis in high-risk clinical settings, including surgery, trauma, and management of pregnancy, labour, and delivery. The goal of treatment for patients with hereditary AT deficiency is an initial increase in AT activity to ≥120% of normal levels followed by maintenance of AT activity at ≥80% of normal levels. Plasma-derived AT, heparin, fresh frozen plasma, and human recombinant AT are treatment options for individuals with hereditary AT deficiency. The objective of this review is to discuss hereditary AT deficiency and the role of AT replacement therapy in the treatment of patients with this congenital disorder.

Iron replacement for iron-deficiency anemia has historically been accomplished with the use of oral iron therapy. Although oral iron is appropriate for most iron-deficiency anemia patients, many patients do not respond to or may be intolerant of oral iron, or may experience bleeding of sufficient magnitude to require higher iron doses than that achievable with oral iron. Intravenous iron therapy is a useful option for these latter patients. Three intravenous iron products are recommended: low-molecular weight iron dextran (INFeD), ferric gluconate (Ferrlecit), and iron sucrose (Venofer). These intravenous iron products have superior safety profiles compared to high-molecular weight iron dextran. The Food and Drug Administration's approval of erythropoietic-stimulating agents to treat certain types of anemia has increased usage of intravenous iron for functional iron deficiency. This review summarizes the current status of intravenous iron products and discusses their advantages and disadvantages in treating both absolute and functional iron deficiency.

A 49-year-old Caucasian woman presented with features suggestive of thrombotic microangiopathy (TMA). She did not respond to treatment with repeated plasma exchange and corticosteroids. A bone marrow biopsy revealed presence of metastatic carcinoma. A limited autopsy revealed presence of breast cancer with rib metastases. Though severe deficiency of von Willebrand factor-cleaving protease was initially proposed as a key pathogenetic factor for thrombotic thrombocytopenic purpura, subsequent studies involving patients with cancer-associated TMA did not find as severe a deficiency of von Willebrand factor-cleaving protease as is seen in idiopathic cases of thrombotic thrombocytopenic purpura. Here we address one approach of management of these patients with cancer-associated TMA.

Anemia is one of the world’s most common disorders. In 2010, global anemia prevalence was 32.9%, affecting over 2.2 billion people, and iron deficiency the most common of the causes.[1][1] Oral iron, while inexpensive and effective when taken and tolerated, is frequently associated with unpleasant

SummaryIntroduction The serotonin release assay (SRA) is considered the gold standard laboratory test for heparin-induced thrombocytopenia (HIT). The historic SRA method uses platelets loaded with radiolabeled serotonin to evaluate platelet activation by HIT immune complexes. However, a nonradioactive method is desirable. We report the performance characteristics of a high-performance liquid chromatography (HPLC) SRA method. Methods We validated the performance characteristics of an HPLC-SRA method, including correlation with a reference laboratory using the radioactive method. Serotonin released from reagent platelets was quantified by HPLC using fluorescent detection. Results were expressed as % release and classified as positive, negative, or indeterminate based on previously published cutoffs. Results Serum samples from 250 subjects with suspected HIT were tested in the HPLC-SRA and with the radioactive method. Concordant classifications were observed in 230 samples (92%). Sera from 41 healthy individuals tested negative. Between-run imprecision studies showed standard deviation of

Our hypothesis is that PGs released within the kidney play a role in the modulation of kidney production of Ep. PGs release probably at medullary and/or cortical sites following erythropoietic stimuli such as hypoxic hypoxia, anemic hypoxia, and ischemic hypoxia induced by renal artery constriction increase kidney production of Ep. PGs which are released probably activate a renal cortical adenylate cyclase thereby enhancing the production of intracellular cAMP. This initiates the cascade of events resulting in the production and/or secretion of Ep by the kidney. The endoperoxide analogs and PGE2 have been found to produce a dose-related and Ep-dependent increase in radioiron incorporation into newly formed red blood cells of exhypoxic polycythemic mice. Indomethacin, a potent PG cyclo-oxygenase inhibitior, attenuates Ep production and the appearance of PGE in the renal venous effluent of animals exposed to hypoxic hypoxia and renal artery constriction. Arachidonic acid (C20:4) and PGE2 infusion into the posthypoxic isolated perfused dog kidney produced a significant elevation in Ep titers in the perfusate. The increase in Ep production caused by arachidonate is blocked by indomethacin. It has been previously reported that PGs of the E series stimulate cAMP formation in several tissues. We have found that not only are renal cortical cAMP levels significantly elevated in rats following exposure to hypobaric hypoxia but that dibutyryl cAMP administration produces an increase in hematocrit and circulating red cell mass in normal mice. Our data thus far strongly support the hypothesis that the renal PGs and the cyclic nucleotides are intimately involved in the pharmacologic and/or pathophysiologic control of Ep production. Further work is necessary to determine whether the PGs and cyclic nucleotides are involved in the day-to-day control of Ep production by the mammalian kidney.