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Background Alloimmunization prevalence is conventionally used to identify RBCs alloimmunization risk factors among thalassemia patients, but it may be confounded by differences in transfusion exposure especially between non-transfusion dependent thalassemia (NTDT) and transfusion dependent thalassemia (TDT) patients. To better identify thalassemia patients with high alloimmunization risks, we used cumulative incidence of first alloimmunization as a function of RBCs transfused to compare alloimmunization risks between TDT and NTDT and to evaluate other risk factors. We also proposed practical strategies to prevent alloimmunization in thalassemia. Study design and methods Adult TDT and NTDT patients who had received ≥2 transfusions and no alloimmunization before their first transfusion were included. Alloimmunization was defined as the development of clinically significant alloantibodies. We estimated the first alloimmunization incidence from transfusion by Kaplan-Meier analysis with the horizontal axis expressed as cumulative non-antigen-matched RBC units transfused. We compared this incidence between TDT and NTDT, and analyzed for other alloimmunization risk factors and the alloantibody specificities/frequencies. Results The alloimmunization prevalence was similar between TDT and NTDT (27% vs. 30% respectively, p = .726). However, for the same transfusion exposure, NTDT had higher alloimmunization incidence than TDT (hazard ratio 8.59, 95% confidence interval [2.25-32.74], p = .002), independent of age at first transfusion and last follow-up, gender, and splenectomy. Anti-E, anti-c, anti-Mia , and anti-Jka were most frequent. Discussion NTDT has the highest alloimmunization risk and would benefit the most from extended RBC antigen-matching, especially C, c, E, and e. Other blood group antigen-matching should be guided by the patient/donor disparities and alloantibody frequencies in different populations.

International audience; Preoperative anaemia is common in the Asia-Pacific. Iron-deficiency anaemia (IDA) is a risk factor that can be addressed under patient blood management (PBM) Pillar 1, leading to reduced morbidity and mortality. We examined PBM implementation under four different healthcare systems, identified challenges and proposed several measures. (a) Test for anaemia once patients are scheduled for surgery. (b) Inform patients about risks of preoperative anaemia and benefits of treatment. (c) Treat IDA and replenish iron stores before surgery, using intravenous iron when oral treatment is ineffective, not tolerated or rapid iron replenishment is needed; transfusion should not be the default management. (d) Harness support from multiple medical disciplines and relevant bodies to promote PBM implementation. (e) Demonstrate better outcomes and cost savings from reduced mortality and morbidity. Although PBM implementation may seem complex and daunting, it is feasible to start small. Implementing PBM Pillar 1, particularly in preoperative patients, is a sensible first step regardless of the healthcare setting.

Background/objectives We compared the ex vivo haemostatic capacity of RTFP24 with FFP upon thawing and >24 h post-thaw. We included thrombin generation (TG) as few studies had compared global haemostatic function, and most did not directly compare RTFP24 with FFP >24 h post-thaw. Materials/methods Twenty units each of RTFP24 and FFP were measured for coagulation factors and thrombin generation upon thawing (D0) and 4 days post-thaw (D4). Labile factors were also measured from D1 to D3. 10 single cryoprecipitate units were each prepared from FFP and RTFP24, and measured for FXIII, FVIII and fibrinogen at D0. Results At D0, RTFP24 was comparable to FFP except for lower FV, protein S, endogenous thrombin potential (ETP) and higher FXIII. These differences were likely clinically insignificant since 95% and 80% of RTFP24 met our laboratory's reference ranges for FV/protein S and ETP, respectively. There were no differences between RTFP24- and FFP-derived cryoprecipitate. At D4, RTFP24 was comparable to FFP except for lower FV, ETP, and higher FXI and FXIII. More RTFP24 than FFP had ETP lower than our laboratory's reference range (45% vs 15%). Multiple coagulation factors and all TG parameters declined from their respective baselines. The percentage declines were comparable or less in RTFP24, except for protein C, fibrinogen and time to peak. Conclusion RTFP24 and FFP, and their derived cryoprecipitate have comparable haemostatic capacity upon thawing. RTFP24 has poorer TG potential than FFP >24 h post-thaw, not supporting universal extension of RTFP24's shelf life except to facilitate urgent transfusions for massive haemorrhage.

International audience

Background and objectives: COVID-19 convalescent plasma (CCP) has been used, predominantly in high-income countries (HICs) to treat COVID-19; available data suggest the safety and efficacy of use. We sought to develop guidance for procurement and use of CCP, particularly in low- and middle-income countries (LMICs) for which data are lacking. Materials and methods: A multidisciplinary, geographically representative group of individuals with expertise spanning transfusion medicine, infectious diseases and haematology was tasked with the development of a guidance document for CCP, drawing on expert opinion, survey of group members and review of available evidence. Three subgroups (i.e. donor, product and patient) were established based on self-identified expertise and interest. Here, the donor and product-related challenges are summarized and contrasted between HICs and LMICs with a view to guide related practices. Results: The challenges to advance CCP therapy are different between HICs and LMICs. Early challenges in HICs related to recruitment and qualification of sufficient donors to meet the growing demand. Antibody testing also posed a specific obstacle given lack of standardization, variable performance of the assays in use and uncertain interpretation of results. In LMICs, an extant transfusion deficit, suboptimal models of donor recruitment (e.g. reliance on replacement and paid donors), limited laboratory capacity for pre-donation qualification and operational considerations could impede wide adoption. Conclusion: There has been wide-scale adoption of CCP in many HICs, which could increase if clinical trials show efficacy of use. By contrast, LMICs, having received little attention, require locally applicable strategies for adoption of CCP.

International audience

Non-transfusion-dependent thalassaemia (NTDT) is associated with a hypercoagulable state with thrombotic risk highest after splenectomy. Various mechanisms have been proposed. Although an antiplatelet agent is commonly recommended as thromboprophylaxis in NTDT, the role of platelets contributing to this hypercoagulable state is not well-defined. This study aims to evaluate the role of platelets contributing to hypercoagulability in NTDT patients using thrombin generation (TG). Platelet-rich (PRP) and platelet-poor plasma (PPP) were collected from NTDT patients (n = 30) and normal controls (n = 20) for TG measurement and compared. Controls had higher endogenous thrombin potential (ETP) in PPP (1204.97 nM.min vs 911.62 nM.min, p

Background A common national MTP was jointly implemented in 2011 by the national blood service (Blood Services Group) and seven participating acute hospitals to provide rapid access to transfusion support for massively haemorrhaging patients treated in all acute care hospitals. Methods Through a systematic clinical workflow, blood components are transfused in a ratio of 1:1:1 (pRBC: whole blood-derived platelets: FFP), together with cryoprecipitate for fibrinogen replacement. The composition of components for the MTP is fixed, although operational aspects of the MTP can be adapted by individual hospitals to suit local hospital workflow. The MTP could be activated in support of any patient with critical bleeding and at risk of massive transfusion, including trauma and non-trauma general medical, surgical and obstetric patients. Results There were 434 activations of the MTP from October 2011 to October 2013. Thirty-nine per cent were for trauma patients, and 30% were for surgical patients with heavy intra-operative bleeding, with 25% and 6% for patients with gastrointestinal bleeding and peri-partum haemorrhage, respectively. Several hospitals reported reduction in mean time between request and arrival of blood. Mean transfusion ratio achieved was one red cell unit: 0·8 FFP units: 0·8 whole blood-derived platelet units: 0·4 units of cryoprecipitate. Although cryoprecipitate usage more than doubled after introduction of MTP, there was no significant rise in overall red cells, platelet and FFP usage following implementation. Conclusion This successful collaboration shows that shared transfusion protocols are feasible and potentially advantageous for hospitals sharing a central blood provider.

L. Lieberman, D. V. Devine, H. W. Reesink, S. Panzer, J. Wong, T. Raison, S. Benson, J. Pink, G. C. Leitner, M. Horvath, V. Compernolle, P. S. Prado Scuracchio, S. Wendel, G. Delage, S. Nahirniak, X. Dongfu, T. Krusius, E. Juvonen, S. Sainio, J.-P. Cazenave, P. Guntz, D. Kientz, G. Andreu, P. Morel, E. Seifried, K. Hourfar, C. K. Lin, J. O’Riordan, E. Raspollini, S. Villa, P. Rebulla, P. Flanagan, D. Teo, S. Lam, A. L. Ang, M. Lozano, S. Sauleda, J. Cid, A. Pereira, B. Ekermo, C. Niederhauser, S. Waldvogel, S. Fontana, M. J. Desborough, R. Pawson, M. Li, H. Kamel, M. Busch, L. Qu & D. Triulzi

Low bone mass, a major cause of morbidity in patients with β-thalassemia major (β-TM), is multifactorial. There is lack of data about the current prevalence of low bone mass in patients with β-TM. The aims of this study are to examine the current prevalence of low bone mass in β-TM patients and the association between demographic characteristics, markers of iron overload, endocrinopathies, glycemic status and bone mineral density (BMD) as well as to study the 25-OH-vitamin D status of the patients and its relationship with BMD. Our institution serves the largest cohort of β-TM patients in the UK. From 99 patients (49 males, 50 females) with a mean ± standard deviation (SD) age of 36 ± 9 years, 55.5% had low BMD for their age as defined by Z-score BMD-2.0 either at the lumbar spine (43.9%) or at the hip (25.5%). The only statistically significant association on the multivariate analysis was between hypogonadism and low BMD at the lumbar spine. In our study, 29.9% of patients had vitamin D deficiency, 65.7% had vitamin D insufficiency and 12.4% had optimal levels. No association between vitamin D status and low bone mass was found. Our study demonstrated a much lower prevalence of low bone mass in adults with β-TM compared to previous studies. Further studies are needed to examine whether this suggests a widespread improvement across patients with β-TM possibly due to advances in therapeutics. Most patients had suboptimal 25-OH-vitamin D levels, but no association between vitamin D status and bone mass was demonstrated.

Endocrinopathies are common complications of transfusional hemosiderosis among patients with β thalassemia major (TM). Previous studies had shown associations between some endocrinopathies and iron overload of the myocardium, liver and/or endocrine organs as assessed by MRI techniques. This retrospective analysis of 92 patients with TM (median age 36 yr) from a tertiary adult thalassemia unit in UK aimed to determine independent risk factors associated with endocrinopathies among these patients. Unlike previous studies, longitudinal data on routine measurements of iron load [worst myocardial and liver T2* values since 1999, worst LIC by MRI-R2 since 2008 and average 10-yr serum ferritin (SF)] up to April 2010 together with demographic features and age of initiating chelation were analyzed for associations with endocrinopathies. The most common endocrinopathies in this cohort were hypogonadism (67%) and diabetes mellitus (DM) (41%), and these were independently associated with myocardial T2*20 ms (P 0.001 and P = 0.008, respectively) and increased age (P = 0.002 and P = 0.016, respectively). DM and hypogonadism were independently associated with average SF1250 μg/L (P = 0.003) and2000 μg/L (P = 0.047), respectively. DM was also associated with initial detection of abnormal myocardial T2* at an older age (30 yr vs. 24 yr, P = 0.039). An abnormal myocardial T2* may therefore portend the development of DM and hypogonadism in patients with TM.

GLUT1 (glucose transporter 1) deficiency syndrome is a well-known presentation in pediatric practice. Very rare mutations not only disable carbohydrate transport but also cause the red cell membrane to be constitutively permeant to monovalent cations, namely sodium and potassium.The aim of this study was to describe the pediatric presentation of a patient with GLUT1 deficiency with such a cation-leaky state.The infant presented with erratic hyperkalemia, neonatal hyperbilirubinemia, anemia, hepatic dysfunction, and microcephaly. Later, seizures occurred and developmental milestones were delayed. Magnetic resonance imaging and computerized tomography scans of the brain showed multiple abnormalities including periventricular calcification. Visual impairment was present due to the presence of both cataracts and retinal dysfunction.Measurements of red cell cation content showed extremely leaky red cells (causing the hemolysis) and temperature-dependent loss of potassium from red cells (explaining the hyperkalemia as pseudohyperkalemia). A trinucleotide deletion in SLC2A1, coding for the deletion of isoleucine 435 or 436 in GLUT1, was identified in the proband.This is the fourth pedigree to be described with this most unusual syndrome. The multisystem pathology probably reflects a combination of glucose transport deficiency at the blood-brain barrier (as in typical GLUT1 deficiency) and the deleterious osmotic effects of a cation-leaky membrane protein in the cells where GLUT1 is expressed, notably the red cell. We hope that this detailed description will facilitate rapid diagnosis of this disease entity.

SummaryAcquired factor V(FV) inhibitors as a rare bleeding disorder, poses a formidable challenge to treating physicians with limited evidence to guide its management. We systematically reviewed our experience in Singapore and the published literature to determine possible answers to clinical questions formulated on the manifestation and best management of non-bovine thrombin and non-congenital acquired FV inhibitors. The incidence in Singapore was 0.09 cases per million person years (3 cases over 10 years). Seventy-three other cases meeting pre-defined search criteria were found in the published literature. Bleeding occurred in 68.4% of these patients, with mucous membranes being the most common site. Intracranial and retroperitoneal bleeds carried the highest mortality. The mortality rate from bleeding was 12%. There was a tendency for FV levels and PT/aPTT prolongation to predict bleeding but not the inhibitor level. No consistently effective haemostatic agent could be determined, but platelet transfusion should probably be the first line therapy. Among bleeding patients, inhibitors tended to disappear faster with inhibitor elimination therapy (IET) compared to without IET (60 vs. 150 days, p=0.299). IET made no significant difference among non-bleeding patients (p=0.511) and is thus recommended for bleeding patients or those with high bleeding risk. Steroids as single agent IET was effective in the majority of patients. Logical management approaches may be drawn but are limited by small sample size, heterogeneity of reports, and potential publication bias. The inception of a comprehensive registry will provide more reliable data that may verify our findings.

Introduction Preoperative anemia and high red cell distribution width (RDW) are associated with higher perioperative mortality. Conditions with high RDW levels can be categorized by mean corpuscular volume (MCV). The relationship between RDW, anemia and MCV may explain causality between high RDW levels and outcomes. We aim to establish the prevalence of preoperative anemia and distribution of RDW and MCV among pre-surgical patients in Singapore. In addition, we aim to investigate the association between preoperative anemia, RDW and MCV levels with one-year mortality after surgery. Methods Retrospective review of 97,443 patients aged > = 18 years who underwent cardiac and non-cardiac surgeries under anesthesia between January 2012 and October 2016. Patient demographics, comorbidities, priority of surgery, surgical risk classification, perioperative transfusion, preoperative hemoglobin, RDW, MCV were collected. WHO anemia classification was used. High RDW was defined as >15.7%. Multivariate regression analyses were done to identify independent risk factors for mild or moderate/severe anemia and high RDW (>15.7). Multivariate cox regression analysis was done to determine the effect of preoperative anemia, abnormal RDW and MCV values on 1-year mortality. Results Our cohort comprised of 94.7% non-cardiac and 5.3% cardiac surgeries. 88.7% of patients achieved 1 year follow-up. Anemia prevalence was 27.8%—mild anemia 15.3%, moderate anemia 12.0% and severe anemia 0.5%. One-year mortality was 3.5%. Anemia increased with age in males, while in females, anemia was more prevalent between 18–49 years and > = 70 years. Most anemics were normocytic. Normocytosis and macrocytosis increased with age, while microcytosis decreased with age. Older age, male gender, higher ASA-PS score, anemia (mild- aHR 1.98; moderate/severe aHR 2.86), macrocytosis (aHR 1.47), high RDW (aHR 2.34), moderate-high risk surgery and emergency surgery were associated with higher hazard ratios of one-year mortality. Discussion Preoperative anemia is common. Anemia, macrocytosis and high RDW increases one year mortality.

Tyrosine kinase inhibitors (TKIs) elicit high response rates among individuals with kinase-driven malignancies, including chronic myeloid leukemia (CML) and epidermal growth factor receptor-mutated non-small-cell lung cancer (EGFR NSCLC). However, the extent and duration of these responses are heterogeneous, suggesting the existence of genetic modifiers affecting an individual's response to TKIs. Using paired-end DNA sequencing, we discovered a common intronic deletion polymorphism in the gene encoding BCL2-like 11 (BIM). BIM is a pro-apoptotic member of the B-cell CLL/lymphoma 2 (BCL2) family of proteins, and its upregulation is required for TKIs to induce apoptosis in kinase-driven cancers. The polymorphism switched BIM splicing from exon 4 to exon 3, which resulted in expression of BIM isoforms lacking the pro-apoptotic BCL2-homology domain 3 (BH3). The polymorphism was sufficient to confer intrinsic TKI resistance in CML and EGFR NSCLC cell lines, but this resistance could be overcome with BH3-mimetic drugs. Notably, individuals with CML and EGFR NSCLC harboring the polymorphism experienced significantly inferior responses to TKIs than did individuals without the polymorphism (P = 0.02 for CML and P = 0.027 for EGFR NSCLC). Our results offer an explanation for the heterogeneity of TKI responses across individuals and suggest the possibility of personalizing therapy with BH3 mimetics to overcome BIM-polymorphism-associated TKI resistance.

More adults undergo extracorporeal membrane oxygenation (ECMO) now. They have high transfusion requirements. This study described transfusion requirements of adults during ECMO in a single institution, and determined factors associated with high transfusion requirements.Retrospective analysis was done on the amount of blood products received by adults during ECMO. Predictors of increased average daily transfusion requirements during ECMO and increased ECMO duration (which correlated positively with total transfusion requirements) were determined.Forty-one patients (median age 50 years) underwent 42 ECMO sessions for respiratory failure (16.7%), cardiogenic shock (76.2%) or massive pulmonary embolism (7.1%). They received 569 red blood cells, 852 platelets, 126 fresh-frozen plasma (FFP) and 220 cryoprecipitate in total during median ECMO duration of 5 (1-15) days. On multivariate analysis, average daily red blood cell transfusion increased with nadir haemoglobin (Hb) during ECMO (Hb(nadir)) of7.5 g/dl (P0.001). Average daily platelet transfusion increased with recent antiplatelet agents (P = 0.015) and maximum Hb decline of5.5 g/dl during ECMO (P = 0.011). Average daily platelet transfusion3 units was also associated with increased ECMO duration (P = 0.024). Average daily FFP transfusion was increased in patients with hypertension (P = 0.007) and Hb(nadir)7.5 g/dl (P = 0.050). Patients with sepsis (P = 0.009) or without surgery (P = 0.009) had increased ECMO duration, which correlated positively with total transfusion requirements during the entire ECMO session. ECMO improved mortality of patients with fulminant myocarditis, respiratory failure and massive pulmonary embolism.Adult ECMO patients with lower Hb(nadir) require more daily red blood cell and FFP. Hypertension increases daily FFP requirements. Recent antiplatelet agents, larger Hb decline and longer ECMO duration increase daily platelet requirements. Patients with sepsis or on ECMO for medical reasons have longer ECMO duration, which is associated with total transfusion requirements. Some of these factors may be identified early to optimize blood product support.

Introduction Daratumumab (DARA), an IgG1k human monoclonal antibody (Ab) against CD38, is a promising novel therapy for multiple myeloma. However, direct binding of DARA to endogenous CD38 on reagent red blood cells (RBCs) interferes with routine blood bank serologic testing. We recently showed that treating reagent RBCs with DTT eliminates the DARA interference by denaturing cell surface CD38, allowing the safe transfusion of patients on DARA.1 This multicenter international study was aimed at validating the DTT method for use by blood banks worldwide. Methods Participating blood banks received two plasma sample unknowns. Sample 1 was spiked with DARA alone (5 mcg/mL). Sample 2 was spiked with DARA plus a clinically significant RBC Ab (anti-D (Rh immune globulin) or monoclonal anti-Fya or anti-s). Sites were instructed to first perform an Ab screen using their usual method (tube, gel, or solid phase), then to repeat the Ab screen using DTT-treated RBCs (gel or tube). If the Ab screen remained positive with DTT-treated RBCs (Sample 2), sites were to identify the unknown Ab using a DTT-treated RBC panel (gel or tube.) The primary outcome measure was the proportion of sites able to successfully identify the unknown Ab in the presence of DARA. Qualitative data were collected by online survey. Results Paired plasma sample unknowns were shipped to 25 study sites in North America, South America, Europe, Asia, and Australia/New Zealand. Data were received from 23 sites to date (Table). For the initial Ab screen, 10 sites used tube testing, 7 sites used gel, and 6 sites used solid phase. All sites observed DARA interference with the Ab screen (false positive agglutination reactions). All sites reported no DARA interference using DTT-treated RBCs. For Ab identification (Sample 2), 13 sites used tube testing and 10 sites used gel. 23/23 sites (100%) were able to correctly identify the unknown Ab using the DTT method. The Abs identified were: anti-Fya (9/9), anti-s (8/8), and anti-D (6/6). Feedback on the DTT method was mainly positive, with 86% of sites that responded to the survey indicating that they planned to use the DTT method to manage clinical samples from DARA-treated patients. Conclusion DARA consistently interferes with all three Ab screening methods currently used by blood banks (tube, gel, and solid phase.) Using DTT-treated RBCs, 23/23 (100%) of blood bank laboratories from around the world were able to identify a clinically significant Ab initially masked by the presence of DARA. The DTT method is robust, reproducible, and can be implemented by blood banks globally to help provide safe blood products to patients on DARA. As DTT denatures Kell antigens, K- RBC units should be provided when using the DTT method. 1. Chapuy CI, Nicholson RT, Aguad MD, et al. Resolving the daratumumab interference with blood compatibility testing. Transfusion. 2015;55(6pt2):1545-1554. Disclosures Unger: Janssen: Employment. Doshi:Janssen: Employment. Kaufman:Janssen: Consultancy, Research Funding.

Abstract 5060 Less than 20% of patients with essential thrombocythemia (ET) are diagnosed below the age of 60. Patients with ET have increased risk of thrombosis and bleeding and potential for progression to myelofibrosis (MF) or acute myeloid leukaemia (AML). In limited studies of young patients, the clinical course has been relatively benign with low rates of transformation to AML or MF. Thrombohemorrhagic events are generally few, but higher than that of the general population. This study aims to characterize of a group ET patients diagnosed at age ≤40, their thrombotic and hemorrhagic events, disease progression and treatment given. Patients were identified through a single institution MPN registry. This is an IRB approved registry that captures comprehensive information about patients with ET. Data on patient demographics, treatment, and disease-related events were obtained. Patients were diagnosed from 1975–2011, using either WHO or PVSG criteria depending on date of diagnosis. Kaplan-Meier method was used for survival analysis. 59 patients were diagnosed with ET at age ≤40. Median age of diagnosis was 31. 5years (range 16–40), with a median follow up of 7. 7years (0. 4–33. 8). All were of Asian descent: 81. 4% Chinese, 11. 9% Malay, 3. 4% Indian and 3. 4% Filipino. 40. 7% were male. JAK2 V617F mutation was screened for in 61%. Of these patients, 11 were positive, 25 negative for the mutation. Mean presenting counts were: WBC 10. 7 × 109/L (5. 9–21. 3), Hb 13. 6g/dL (9. 7–16. 4), platelets 957 × 109/L (449–2377). Splenomegaly was noted in 3 patients. 20. 3% had underlying hypertension, 16. 9% hyperlipidemia and 5. 1% diabetes mellitus. One patient had a prior stroke. Another had prior portal vein thrombosis. At diagnosis, 23. 7% were symptomatic, with microvascular symptoms of headache (11. 9%) and giddiness (6. 8%) being most common. The remainder were diagnosed incidentally, on health screening or when seeking medical attention for unrelated conditions. One patient presented with a myocardial infarction at diagnosis, while another had a significant bleeding post hemorrhoidectomy with drop in Hb by >2g/dL (platelet 2457 × 109/L). Based on a history of prior thrombosis, 3 patients were defined as high risk for thrombotic events. 67. 8% of patients had cytoreduction, indications being platelets ≥1500 × 109/L (n=16), presence of risk factors for atherosclerotic disease (n=11) and history/onset of thrombosis (n=5). In 8, the reason for cytoreduction could not be ascertained. Hydroxyurea was most commonly used (62. 7%), followed by anagrelide in 52. 5% and interferon 25. 4%. 5. 1% received busulphan, and 1. 7% 32P. Use of antiplatelet therapy was noted in 83. 8%, most frequently aspirin (76. 5%) and ticlopidine (11. 9%). On follow up, 2 arterial thromboses occurred (stroke, TIA), giving a thrombosis rate of 0. 39%/patients/year. Neither was a recurrent thrombosis. No venous thrombosis or major bleeds occurred. 20. 4% had minor mucocutaneous bleeding; 5 had platelets ≥1500 × 109/L at that time. 3. 4% had disease progression due to MF and another 3. 4% had AML. 3. 4% of patients died due to AML. Median survival was 33. 8years (95% confidence interval 30. 3–35. 5). Initial blood counts, presence of JAK2 and high risk disease status did not correlate with thrombotic risk, risk of death or disease progression. Use of antiplatelet agents and a platelet count ≥1500 × 109/L did not correlate with bleeding risk. Few studies have looked exclusively at young patients with ET. In this group, most patients were asymptomatic and well, ET being diagnosed incidentally. They were predominantly at low risk for thrombosis and other ET-related complications. The period of follow up was comparable to that of other studies and during that time, the rate of complications and risk of disease progression was low. The thrombosis rate of 0. 39% per patient year was less than that reported by other groups (2. 2–2. 6 thromboses/100patients/year) (Leukaemia 2007;21:1218–1223, Clin Appl Thrombosis/Hemostasis 2000;6(1):31–35) but similar to the 0. 74%/patient year reported by Barbui (Blood. Epub. June 13 2012). Overall findings generally complemented those reported by other groups. No risk factors were found to influence the occurrence of complications, but the number of events was small. Follow up of this group of patients over time is essential to see if their disease course remains benign or if complications will increase with time. Soli Deo Gloria Disclosures: Kam: Shire Pharmaceuticals: Consultancy, grant to support the MPN registry Other.

Abstract 1011 Background. CMR was introduced in London to assess myocardial iron loading in 1999 and some of these patients now have 10 years of follow-up, most with contemporary CMR determinations. The impact of long-term monitoring of myocardial iron loading in thalassemia major (TM) on the proportion of patients with increased myocardial iron (cT2* Patients and Methods. All patients regularly attending two London thalassemia centres, who received their first CMR Jan 1999 - Dec 2000 were analyzed as a cohort. Patients underwent initial CMR at the Royal Brompton Hospital and received CMR follow up (FU) either there or at the Heart Hospital (UCLH). 132 patients were identified as having received a CMR in 1999–2000. A minimum 7 years CMR FU was required for inclusion in the long-term CMR analysis. 109 patients had at least 7 years of CMR follow up (range 7.0–10.6 years, median 9.2). The median age at 1st CMR was 27.9 years (range 7.7 – 49.5 years). At baseline, patients were receiving chelation with deferoxamine (DFO) monotherapy (70%), deferiprone (DFP) monotherapy (21%), or a combination of these agents (9%). At latest FU, patients were receiving DFO (32%), deferasirox (DFX) (28%), DFP (22%), or combined DFP and DFO therapy (18%). Results: Improvement in cardiac iron: In 1999–2000, 60% of TM patients had cT2* values ≤20ms and 17% had cT2* values Changes to chelation therapy: 31% of patients stayed on the same chelator; 33% had 1 chelator switch, 26% 2 switches and 11% 3 or more switches. 18 switches in chelation therapy were due to side-effects (12 DFP, 5 DFX, 1 DFO). There were 9 breaks in chelation therapy during pregnancy in 8 different women. The proportions of patients with T2* < 20ms fell significantly for those who remained on DFO or DFP monotherapies throughout, or who changed chelation modalities on only one (p=0.002) or two (p=0.02) occasions. Patients who received had 3 or more switches did not show a improvement in this respect. The latter group was also the only subset that showed significant deterioration in myocardial iron (p Mortality rates: the overall mortality rate for the initial cohort was 1.65 per 1000 patient years (95% CI 0.71 – 3.24); median age at death 35.6 years (range 27.3–48.4). This is a substantial improvement in the mortality index compared with the UK thalassemia registry data, of 4.3 per 1000 patient years during the period 2000–2003 (Modell et al, JCMR, 2008). The incidence rate ratio is 0.387 (95% CI 0.11–0.961), p Causes of death: there were 8 deaths during the FU period: 3 with complications of hepatitis C (all with cT2* > 20ms), 3 with sepsis (2 with cT2* 20ms). Thus in only 2 patients could excessive cardiac iron loading be considered a causal/contributory factor. There was no significant difference in the baseline cT2* between those who died and those currently still alive (p= 0.2), meaning that death as a drop-out cause does not explain iron loading trends over FU. Chelators at death: DFO (4), DFP (2), DFX (1), combination (1). Conclusions: Over a decade we have seen an almost 3 fold fall in the proportion of patients with myocardial iron overload. Mortality has become substantially lower and cardiac iron overload is no longer the leading cause of mortality. In addition to CMR, this decade has seen the advent of two new oral iron chelators and many patients switched chelation regimen, sometimes several times, during the follow up period. Whilst the contribution of the individual components of this practice to the improved outcome cannot be concluded without randomized studies, it is clear that this modern management of TM is associated with reduced TM mortality. Disclosures: Off Label Use: Deferiprone is off label in the USA but licensed in Europe. Shah:Novartis: Honoraria, Speakers Bureau; Apotex/ Swedish Orphan: Honoraria. Pennell:Siemens: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Apotex: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Cardiovascular Imaging Solutions: Director of CVIS, Equity Ownership. Porter:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Abstract 1666 The use of the tyrosine kinase inhibitor (TKI), imatinib (IM), to target the oncogenic BCR-ABL kinase has resulted in profound responses in patients with chronic phase (CP) chronic myelogenous leukemia (CML). However, a subset of patients do not respond to TKIs, and are deemed to have primary resistance. Importantly, patients with European LeukemiaNet (ELN)-defined ‘failure’ or ‘suboptimal response’ are at increased risk of poorer long-term outcomes. Little is known about mechanisms underlying primary resistance, where only a minority of patients have BCR-ABL kinase domain (KD) mutations. Interestingly, East-Asian CML patients are reported to have lower complete cytogenetic response rates compared to the West (∼50 vs 80% respectively, Au et al. 2009). We used massively parallel DNA sequencing of paired-end ditags to identify genetic factors associated with resistance in CML patient samples. We discovered a novel deletion polymorphism in the BIM gene that correlated with resistance, and which represented a common polymorphism in normal East-Asian (12.3% carriers), but not African or Caucasian (0%), populations (n=2465). BIM is a pro-apoptotic BCL2 family member, and plays a central role in CML pathophysiology. Here, BCR-ABL suppresses FoxO3a-mediated BIM transcription to maintain a survival advantage, while preventing BIM expression following BCR-ABL inhibition results in TKI resistance. Inspection of BIM gene structure suggested the polymorphism would result in mutually exclusive splicing of exon 3 (E3) vs 4 (E4), leading to decreased expression of BIM transcripts encoding the pro-apoptotic BH3 domain (found only in E4). To test this hypothesis, we constructed a minigene to measure E3 vs E4 splicing, and found the polymorphism decreased splicing to E4 over E3 by >5-fold. Importantly, primary CML cells exhibited the same phenomenon, since polymorphism-containing samples expressed lower levels of E4- vs E3-containing transcripts (p=0.008), while general BIM transcription was unaffected. Our observations suggested a novel mechanism for intrinsic TKI resistance. Here, upon IM exposure, polymorphism-containing CML cells would favor induction of E3- vs E4-containing BIM transcripts, decreased expression of BH3-containing BIM isoforms, and impaired apoptosis. To facilitate these studies, we identified a Japanese CML cell line, KCL22, which contained the polymorphism, and confirmed it had a decreased E4/E3 transcript ratio compared to cells without the polymorphism. KCL22 cells also had decreased induction of E4-containing transcripts following IM, as well as lower levels of BIMEL protein, a major BH3-containing BIM isoform. Consistent with prior reports, KCL22 cells were resistant to IM, despite effective BCR-ABL inhibition, and had impaired apoptotic signalling upon IM exposure. Importantly, and as predicted by our model, pharmacologic restoration of BH3 activity (using the BH3-mimetic drug, ABT-737) sensitized cells to IM-induced death. Next, we used zinc finger nuclease-facilitated gene targeting to precisely create the polymorphism in the BIM gene of IM-sensitive K562 CML cells. We generated subclones that were heterozygous or homozygous for the polymorphism, and confirmed a decreased E4/E3 ratio in these cells in a polymorphism-dosage-dependent manner. Polymorphism-containing cells exhibited decreased induction of E4-containing transcripts following IM exposure, as well as impaired upregulation of BIMEL protein, and diminished apoptotic cell death. As in KCL22 cells, ABT-737 enhanced the ability of IM to activate apoptosis in polymorphism-containing cells. Using an expanded East-Asian CML cohort (n=203), we found the polymorphism correlated with TKI resistance (defined as ‘failure’ or ‘suboptimal’ per ELN criteria) in CP patients treated with 400 mg IM daily (p=0.02). Further, patients with the polymorphism were more likely to have resistance in the absence of a KD mutation than those without (OR=2.24, 95% CI of 1.22–4.12). In sum, we have found an East-Asian polymorphism in BIM that is associated with intrinsic resistance to TKIs. Screening for this polymorphism may be useful in identifying patients at risk of TKI resistance; a resistance we show can be overcome by BH3 mimetics. Our findings may also apply to other cancers and proliferative disorders in which drug-sensitivity is BIM-dependent. Disclosures: No relevant conflicts of interest to declare.