ALBERT

Description: Introduction: Genetic counseling in sickle cell disease (SCD) allows to inform people about the genetic condition and to make informed decisions about screening and treatment opportunities. With improvement of care and follow-up of SCD and in order to provide adequate genetic counseling, the current study compared the clinical presentation of patients with hemoglobin SC disease (SC) and sickle cell anemia (SS) or SBeta°-thalassemia (Sβ°). Methods: The Belgian SCD Registry currently includes patients followed in 8 centers. Data was retrieved retrospectively from their medical charts until 2008. From 2008 till December 2012, all data (known and new cases) was prospectively entered. Data was collected either from birth, for patients diagnosed by means of the neonatal screening program (NSP) or from diagnosis following the first contact in a center and consistently until the last follow-up (FU) visit, or death. Data included genotype, demography, method and date of diagnosis, SCD-related complications, biological parameters, radiological results, treatment and hospitalizations. Results: Among the 469 patients recorded, 36 (8%) were SC. Their demographic and outcome data are given in Table 1, subgroups of SC patients detected at birth or not are given in Table 2. FU was 292 and 4749 patient-years (PY) for SC and SS/Sβ° groups respectively. Median age at diagnosis for SC and SS/Sβ° subgroups not detected at birth was 6.7 and 2.6 y. The first vaso-occlusive crisis (VOC) in SC patients occurred earlier in neonatal screened patients (5y vs 17y; P=0.004). Osteonecrosis was observed only in 6 patients diagnosed at birth but was significantly more frequent in SC individuals (P=0.02). Among the 6 SC patients treated with hydroxyurea (HU), indications for treatment were recurrent VOC (n=4), proteinuria (n=1) and osteonecrosis (n=1). Hospitalization days per 100 PY were 123 for the SC NSP cohort and 373 for the SS/Sβ° NSP cohort, with total hospitalization days significantly lower in SC patients (160 vs. 4059 days ; P=0.03). Discussion: SC patients represent 8 % of the whole cohort but asymptomatic and undiagnosed patients probably exist. Overall they are much less represented than in other Western series. They are significantly less affected by VOC, acute chest syndrome (ACS), severe anemia than SS/Sβ° patients but did not differ for occurrence of retinopathy or osteonecrosis. Several published studies confirmed these data but showed also others complications such as severe infection, stroke and death. Our data doesn’t support any impact of NSP on occurrence of major complications for SC disease. Retinopathy incidence that increases with age is as expected lower in the NSP group (younger patients at last FU when compared to no NSP group). Older age at first VOC in the no NSP group results probably from previously undiagnosed mild disease. Nevertheless several SC patients were more severely affected requiring HU treatment. Limitations of our work are linked to the small size of our SC cohort, the nature of the partial retrospective study and the unknown number of SC patients not requiring care in a specific program. In conclusion, SC patients have a lower incidence of clinical events than SS/Sβ°, excepted for osteonecrosis and retinopathy equally observed in both groups. Our data support the need of early ophthalmological FU and special awareness to detect early osteonecrosis. These Belgian data may support a dedicated genetic counseling for SC patients and affected families. Table 1. SC and SS/S β 0 patients: demographic and outcome SC SS/Sβ0 P Number of patients 36 (8%) 423 (90,2%) Male 14 (39%) 201 (48%) NS NSP 19 (53%) 142 (34%) Median age at diagnosis years (range) 0 (0-35) 1 (0-29) NS Median age at last FU years (range) 9,9 (1,4-44) 13 (1-53) NS Severe anemia 〈 60g/L 3 (8%) 208 (49%) 〈 0,01 ACS 1 (2,8%) 119 (28%) 〈 0,01 VOC 11 (31%) 253 (60%) 〈 0,05 Stroke 0 17 (4%) NS Severe infection 0 35 (8%) NS Osteonecrosis 4 (11%) 36 (8,5%) NS Retinopathy 4 (11%) 25 (6%) NS HU treatment 6 (17%) 179 (42%) 〈 0,05 Deaths 0 13 (3%) NS Table 2. SC patients from NSP vs no NSP: demographic and outcome NSP no NSP P Number of patients 19 (53%) 17 (47%) Male 10 (53%) 4 (24%) NS Median age at last FU years (range) 6 (1-14) 14 (4-44) NS Severe anemia 〈 60g/L 2 (10,5%) 1 (6%) NS ACS 0 1 (6%) NS VOC 5 (26%) 6 (35%) NS Osteonecrosis 3 (16%) 1 (6%) NS Retinopathy 0 4 (23,5%) 0,04 Disclosures No relevant conflicts of interest to declare.

Description: Introduction: In recent studies,interleukin-3 receptor alpha chain (IL-3Rα or CD123) has been described as over-expressed on leukemia progenitor/stem cells and low or absent on normal hematopoietic stem cells suggesting that IL-3Rα could represent an important target for the development of new anti-leukemic drugs and a minimal residual disease (MRD) marker. However, CD123 expression on blast cells and its prognostic value in different hematologic malignancies as acute myeloid leukemia (AML), acute lymphoid leukemia (ALL) and refractory anemia with excess blasts (RAEB) are still controversial. In the present study, we retrospectively analyzed the CD123 and other lineage infidelity markers (LIM) expression on blast cells in bone marrow or blood samples from patients with AML, ALL or RAEB and the disease evolution including overall survival of these patients. CD123 was also measured on B-precursors. Methods: Ninety-seven patients suffering from hematologic malignancies including69 AMLs, 21 ALLs (18 B-ALLs and 3 T-ALLs) and 7 RAEBs were retrospectively analyzed in regard to CD123 (clone-FITC 763, BD Pharmingen) and other LIM expression measured by flow cytometry (FCM) on myeloid and lymphoid blasts from 2011 to 2014. CD123 was also analyzed on patients with hematogones (n=23). FCM was performed on 5 and 10-colour flow cytometers with extensive panels to precise leukemia-associated aberrant immunophenotype (LAIP) and blast populations were identified by CD45 vs. side scatter characteristics. The positivity of markers was considered at a threshold of 20%. Results: Among the 97 patients (including 45 deceased, 42 alive and 10 lost in follow-up patients), 54 (55.7%) had a CD123 over-expressed (including 21 deceased, 26 alive and 7 lost in follow-up patients). Forty-five patients with AML (n=69) had a CD123 over-expressed (65.2%). Among these 45 patients, 6 were lost in follow-up and 25 were in refractory/relapse disease or dead. Six patients, including 5/18 B-ALL (27.8%) and 1/3 T-ALL (33.3%), with ALL (n=21) had a CD123 over-expressed (28.6%). Among these 6 patients, 5 were in refractory/relapse disease or dead. Three patients with RAEB (n=7) had a CD123 over-expressed (42.86%). Only over-expressing CD123 patients with RAEB are still alive among the 7 RAEBs. The mean value (+/- SD) of the %CD123 on CD45low in all and in the CD123 positive cases of AML, ALL and RAEB was respectively 35.1 +/- 30.5% and 51.4 +/- 25.5%,18.1+/- 31.1% and 61.2 +/- 27.3% , 29.9 +/- 30.7% and 60.1 +/- 20.5%. CD123 over-expression was not observed on B-precursors. Among the 56 patients undergoing long-term follow-up, 10 shifts (17.9%) and 3 inversed shifts (5.4%) were observed in the CD123 expression. Among all, AML, ALL and RAEB patients, respectively 41 (42.3%), 36 (52.2%), 3 (14.3%) and 2 (28.6%) had LIM with respectively 27 (65.8%), 23 (63.8%), 2 (66.7%) and 2 (100%) patients with CD123 over-expression. Only 14.4%, 18.8%, 4.7% and 0% of respectively all, AML, ALL and RAEB patients demonstrated LIM without CD123 over-expression. Conclusions: Our observations confirm that IL-3Rα is very frequently expressed on leukemia blast cells, in about 2/3 of AMLs and probably in 1/3 of ALLs with a rare loss of expression with antigenic shift of the disease. As expected, CD123 is not expressed on hematogones. CD123 seems actually represent one of the most robust markers to follow MRD with FCM, in AML, ALL and RAEB. No significant association betweenCD123 expression and poor overall survival is clearly observed although CD123 expression seems associated with high relapse rate in ALL. Further prospective investigations are needed to assess the real impact of CD123 expression on disease-free and overall survival. Disclosures No relevant conflicts of interest to declare.

Description: Introduction: Previous studies reported that patients with sickle cell disease (SCD) present with alterations of several factors involved in the coagulation system but also that global hemostatic potential parameters are enhanced in children with SCD suggesting hypercoagulability even at steady state. Such modifications have rarely been studied in adult SCD cohorts or individuals with a sickle cell trait (AS). On the other hand, observation of clinical events suggests that SCD adults patients are at higher risk of thrombosis, while those AS are at higher risk of deep venous and pulmonary thrombosis as well as sudden death after intense physical activity. The aim of our study was to characterise the global haemostatic potential of SS and AS adults. Materials and Methods: Three groups were studied and consisted in 31 controls (group AA), 26 sickle cell trait (group AS) and 29 SCD patients (group SS) at steady state. Hemoglobin phenotype was assessed by combination of cation-exchange high performance chromatography (beta-thal short program BioRad) and capillary electrophoresis (Capillarys systems Sebia Benelux). We used the Calibrated Automated Thrombogram® to measure thrombin generation (TG) on platelet poor plasma (PPP) processed, aliquoted and frozen until needed for further testing in batches. TG was triggered using 1 pM tissue factor (TF) and 4µM phospholipids (PL) in two different conditions: with and without addition of thrombomodulin (TM). The interquartile range for several monitored parameters, namely lag time (min), time to peak (min), velocity index (nM/min), endogeneous thrombin potential (ETP, nM.min) and peak (nM) was compared between the 3 groups using Kruskall-Wallis and Dunn's multiple group comparison tests. Protein C activity (PC), free protein S (PS), factor VIII (FVIII), LDH, Thrombin anti-thrombin complex (TAT) and ultrasensitive CRP (CRP us) were also measured in parallel. Informed written consent was obtained from each subject prior to sampling; the study received approval from the local ethics committee. Results: Without TM, there was a significant difference in peak, velocity index and lag time between the 3 groups (p

Description: Survival among children and adults with SCD in Belgium published in 2015 showed a low mortality rate (0.25/100 patient years (PY)) among the 469 patients included (5,110 PY) with no significantly increase above 18 years of age. Hydroxyurea (HU) had a positive impact on patients' survival rate when compared to those without disease-modifying treatments (DMT) or transplanted. This led us to compare the incidence of acute complications and hospitalizations among children and adults to see if significant change occurred. Complications before and after the age of 18 for 84 patients with severe genotype followed after 18 years of age and not transplanted for whom the data during childhood were recorded in the registry are detailed in Figure 1 and Table I. Data on the pre- and post-18 years' events for the entire severe genotype cohort are detailed in Table II and include data from the patients under 18 years and data at the pediatric age of those more than 18 years. Data was censored from the time of the transplantation. Furthermore, data from adult patients before age 18 and beyond with severe genotype treated or not with HU are given in Table III. There were 139 patients (1759 PY) more than 18 years who had at last follow up a median age of 21 years (range: 18-53 years). 42% (59/139) of the patients were treated with HU. The median number of vaso-occlusive crisis (VOC) was statistically lower during adulthood (0 vs 29.6/100 PY; p= 0.007) and the median number of acute chest syndrome (ACS) was not statistically higher in adult period compared to their follow-up during childhood. Overall, severe infections as well as hospitalizations number (19 vs 63/100 PY; p=0.0006) and days (119 vs 259/100 PY; p=0.021) are significantly higher in children. The comparison of adults under HU and without DMT showed a significant higher incidence of acute events in HU patients (Table III). This is true for follow-up in childhood and beyond the age of 18 (Table III). Patients without DMT obviously seems to have attenuated symptomatology (clinical phenotype not very severe despite their severe genotype) and were therefore not considered benefiting from DMT. In the latter, no ACS was recorded during their follow-up in adulthood (Table III). The increase in CVO and ACS incidence with age is well described in the literature but not found in our results. Higher number of hospitalizations and infections before 18 years of age are observed. This can be explained by the fact that children consult more quickly and frequently and they are more readily monitored in hospital compared to adults. They also live in community, which increases the risk of seasonal viral infections. Compared with data available in the literature, our adult patients, most of whom are treated with HU, have fewer acute complications. Nevertheless the comparison is jeopardized because of different methodological approaches. In addition, our cohort of adult patients is limited, has a relatively short follow-up and consists mainly of adults under 21 at the last follow-up. The shorter length of follow up and the underrepresentation of older adults who pay a heavier toll on SCD because of co-existence of chronic complications, may explain the reduced incidence of acute complications in our cohort. In conclusion, the incidence of events observed in our adult population is lower than that described in the literature. This difference is probably related to a larger proportion of HU patients in our cohort. But these results should be confirmed by data from a larger number of adult patients with longer prospective follow-up. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4840 Background Several components of the clotting system are modified towards hypercoagulability in sickle cell disease (SCD). To date, bone marrow transplantation is the only validated curative treatment of SCD. To our knowledge, whether hypercoagulable state reverse to normal following Hematopoietic Stem Cell Transplantation (HSCT) has never been explored. Objective To study changes in pro- and anticoagulant factors, the global haemostatic potential and microparticle (MP) levels following HSCT in SCD children. Patients and Methods Four children with severe SCD were explored before and 3 months after HSCT. They were 2 females (6 and 11 years old) and 2 males (6 and 12 years old). Platelet-poor plasma was prepared from 0.109 M citrated blood after a double centrifugation. Before HSCT, patients were suffering from cerebrovascular disease (2), recurrent acute chest syndrome (2) and frequent vaso-occlusive crises (3). Determination of pro- and anticoagulant factor levels were performed using routine assays on the STAR ® automate. The global haemostatic potential was explored using the Calibrated Automated Thrombogram® method of thrombin generation. Thrombin generation was triggered using 5pM tissue factor and 4μM synthetic phospholipids (PL) with and without 6nM thrombomodulin (TM). Additional experiments were performed using 5pM tissue factor alone. Procoagulant activity of MPs was determined using a capture-based method. Total annexin V positive (A5 MP), red blood cells (RBC MP) and platelets (PLT MP) microparticle levels were measured using a FascCanto II flow cytometer. Calibration was performed using Megamix® beads. RBC MPs and PLT MPs were detected using labeled antibodies directed against glycophorin A and CD42 respectively. Results Results of pro-and anticoagulant factor levels are presented in the figure. Those of D-Dimer levels, thrombin generation and microparticle levels are presented in the table. Three months after HSCT, levels of procoagulant factors VII, V, X, and II, protein C activity, free protein S and antithrombin were higher whereas D-dimers, A5 MP, RBC MP and PLT MP levels were lower in all patients as compared to before HSCT. For 3 of them, endogenous thrombin potential (ETP) and peak height were lower in the presence of thrombomodulin as well as factor VIII levels, and the procoagulant activity of MPs. Reduction of ETP in the presence of thrombomodulin was higher after HSCT. When thrombin generation was triggered without addition of exogenous phospholipids, the peak was lower in all patients whereas ETP was reduced in 2 patients. Data are expressed as median (range). Conclusion Although the number of patients included is too small to allow statistical analyses, the results of this preliminary study showed that there is a trend toward the resolution of the hypercoagulable state of SCD 3 months after successful allogeneic HSCT. Indeed, after this procedure, we observed a trend toward the reduction of the consumptive coagulopathy as shown by higher levels of pro- and anticoagulant factors and lower D-dimers levels. We also observed a trend toward an improvement of the coagulation imbalance as shown by lower thrombin generation, higher response to thrombomodulin and reduced levels of procoagulant MP deriving both from red blood cells and platelets. These findings need to be confirmed with more cases and longer follow-up especially when patients are no more under Ciclosporin A. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4762 Introduction: Abnormalities of the clotting system are often observed in sickle cell disease (SCD). In addition to activation of coagulation, increased thrombin generation (TG) has recently been demonstrated in SCD children Aim of the study: To characterize the group of SCD children with increased TG in terms of clinical and biological parameters. Material and methods: TG was performed in the platelet-poor plasma of 97 SCD children at steady-state and 80 controls aged between 2 and 20 years. TG was triggered using 1 pM tissue factor and 4μM synthetic phospholipids with thrombomodulin to activate the protein C/protein S anticoagulant pathway. The Endogenous Thrombin Potential (ETP) and the peak height were analyzed. As these parameters increase with age in normal children, controls were distributed in 4 categories of age: [2–5], [6–10], [11–15] and [16–20] years. The mean ETP and the mean peak were calculated for each age category. A ratio for ETP (r ETP) and a ratio for the peak (r Peak) were defined for each control and patient as follows: individual ETP/ mean ETP and individual peak/ mean peak according to age category. Overall mean of r ETP and r Peak was then calculated such as to eliminate bias due to age. This calculated mean was 1.00 (0.39 – 1.61) for r ETP and 0.99 (0.28 – 1.81) for r Peak in controls. TG was considered abnormal if r ETP or r Peak value was above the mean + 2SD of controls (r ETP≥ 1.62 and r Peak≥ 1.82). Clinical and laboratory parameters were compared between SCD children having normal or increased ratios using the Mann Whitney test for numbers or the Fisher's exact test for proportions. P 〈 0.05 was considered significant. Results and Discussion: Overall 48 (49.4 %) patients showed either high r ETP or high r Peak whereas both parameters were increased in 31 (31.9 %) patients. As shown in Tables I and II, SCD children with elevated ratios were characterized by a younger age, shorter duration of hydroxyurea (HU) treatment, lower total hemoglobin level, higher reticulocyte and monocyte counts, higher LDH and D-dimer levels and a trend to increased procoagulant microparticle level (PMP) as compared with those having normal ratios. The higher D-dimer level in the group with abnormal ratios indicates that these children also manifest a higher degree of coagulation activation than those with normal ratios. Differences observed with markers of hemolysis are consistent with other reports suggesting a link between hypercoagulability and high hemolytic rate in SCD. The borderline significance of PMP is probably due to the use of exogenous phospholipids in TG which reduces the sensitivity of the test to endogenous phospholipids at the surface of PMPs. Conclusion: According to our study, Elevated Thrombin Potential is more frequently encountered in SCD children of younger age, with a shorter duration of HU treatment and with increased rate of hemolysis. These observations together with elevated D-dimer level seem to characterize SCD children with a hypercoagulable state. Disclosures: No relevant conflicts of interest to declare.

Description: Introduction Cerebral angio-MRI is required in children with Sickle Cell Disease (SCD) in case of abnormal blood flow velocities or lack of acoustic window at Trans-Cranial Doppler Echography (TCD) and to screen the presence of silent infarcts. MRI in young children requires deep sedation and could potentially lead to hypoxemia and increase the risk of SCD-related complications. For this reason, we studied whether deep sedation (DS) for cerebral MRI in young children with SCD might be associated with more frequent adverse events during and within 30 days after the procedure. Methods We identified all patients with SCD who were investigated by MRI under DS in our center (Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium) from Augustus 2005 to March 2016. Demographic data as well as data about the anaesthetic procedure and acute clinical events 30 days before and after sedation have been collected retrospectively. The anaesthetic procedure for patient with SCD was based on midazolam as premedication followed by propofol for deep sedation. Supplementary oxygen was added to all children to maintain FiO2 〉 40%. No prophylactic red blood cell transfusion/exchange were administered before sedation. Data were analyzed for normality; parametric values were assessed by mean and SD, non-parametric values were assessed as medians and interquartile ranges. Student test was used to analyse continuous variable and Chi-square test for discrete variable. Results Seventy four SCD children were identified in whom 147 procedures were performed. 53% were female; 94% were HbSS or HbSβ0. Most of them have already experienced one or more previous acute clinical event (dactylitis 32.4%, vaso-occlusive crisis [VOC] 45.9%, acute chest syndrome [ACS] 32.4%). Hydroxyurea has been prescribed to 39 patients (52.7%) at a median age of 2.4 years (range: 0.6- 4.9 years) mainly for recurrent VOC/ ACS. Five patients were on chronic transfusion program beginning at a median age of 2.6 years (range: 2.1-4.7 years) for primary and secondary stroke prevention. Median age at procedure was 3.1 years (range: 0.9 - 6.1 years). The median number of MRI under DS per patient was 1.8 (range: 1-5). Seven MRI were associated to an incident linked to the DS: 3 episodes of agitation/irritability, 4 desaturations 〈 95% (with 1 requiring transient manual mask ventilation). Median saturation during the procedure was 100% (range: 84-100%). 28 clinical events (19%) occurred within the 30 days before DS while 16 (11%) occurred within the 30 days after DS. Considering hospitalisations, the number were 16 (11%) and 11 (7.5%) before and after respectively. Considering only VOC and ACS, the numbers were 8 (5.4%) before and 6 (4%) after DS. Patients developing SCD complications after DS were less frequently treated with hydroxyurea (18.8% vs. 44.3%, P=0.06), had longer procedure while Hb level, WBC count, MCV, HbF and LDH were not significantly different. Discussion Deep sedation with midazolam and propofol for Cerebral angio-MRI in SCD children was safe, with few side-effects and no increase of VOC and ACS within one month of sedation. Only one study analyzed the safety of deep sedation in young children with SCD (Belmont et al. J Pediatr May 2015; 166:1226-32) but reported a possible trend of increased complications after sedation with midazolam, phenobarbital and fentanyl. Compared to the series of Belmont (Table 1), our patients were younger, more often treated with hydroxyurea and had a shorter procedure duration with less deep desaturation. The combination of propofol with midazolam seems to be better tolerated by children with SCD than midazolam, pentobarbital and fentanyl and appears to be safe in very young children. Disclosures No relevant conflicts of interest to declare.

Description: Newborn sreening (NS) for sickle cell disease (SCD) is effective in reducing early mortality and morbidity through education, prevention of infections and strategies to prevent stroke in children at risk of cerebral vasculopathy. Universal NS was implemented in all Brussels maternity wards since 2000. All identified children with SCD benefited from comprehensive medical care in dedicated centers. This retrospective study included all children with SCD diagnosed through NS and born between January 2000 and December 2005 (Group 1) and between January 2010 and December 2015 (Group 2) followed at Hôpital Universitaire des Enfants Reine Fabiola (Brussels, Belgium). Only patients whose parents consented to be recorded in the Belgian SCD database were eligible for this study. The aim of our study was to compare the outcome of 2 NS cohorts born at 10 years of interval. Demographic data, baseline hematological values and clinical events, occurrence of cerebral vasculopathy and prescription of disease-modifying treatments during the first 5 years of life were compared between both groups. Data were collected until March 1, 2019. 59 patients were identified for this study (35 in Group 1 and 24 in Group 2). Their characteristics are detailed in Table 1. Two patients in Group 2 did not completed the full 5-year evaluation period. Among these 59 patients, 77.9% patients developed at least one SCD clinical event before the age of 5. The number of patients who developed a specific clinical event as well as their age at this first event was the same between the 2 groups (Table 2). The hospitalization number and hospitalization days were not statistically different in the 2 groups (5 vs 4 hospitalizations during 5 years and 19 vs 17 days of hospitalization between Groups 1 and 2 respectively). 3 patients presented an overt stroke (1 in Group 1 and 2 in Group 2) with a global incidence of 1.02 stroke per 100 patient-years. No death was reported in both groups. The proportion of patients with abnormal transcranial doppler velocities decreased slightly in Group 2 (14.3% vs 8.3%, P=0.69) with more conditional velocities (5.7% vs 20.8%, P=0.10) but it was not statistically significant. 60% of patients in Group 1 were treated with hydroxyurea (HU) compared to 75% in Group 2 (P=0.27). HU was introduced at a median age of 2.5 (0.9-4.8) and 2.3 (0.8-4.8) in Groups 1 and 2 respectively (P=0.79). One patient from each group underwent an hematopoietic stem cell transplantation at 4.9 and 3.5 years. Hematological values were not different in the 2 groups excepted for platelets count, which were significantly lower in Group 2 (421 x 10³/µl vs 331 x 10³/µl, P=0.03). Moreover in patients under HU, platelet and reticulocytes count were statistically lower and HbF higher in Group 2 compared to Group 1 (Table 3). Nearly 80% of patients presented a clinical event before the age of 5. This is comparable to what is described in the literature. The Kaplan-Meier survival curves were not statistically different in both groups for the occurrence of a first dactylitis (P=0.52), a first vaso-occlusive crisis (P=0.22) and acute chest syndrome (P=0.37). No more difference was observed for acute anemia (P=0.43), severe infection (P=0.35) or patients under HU (P=0.40). Even if the number of patients on hydroxyurea is not statistically higher in Group 2, a better exposure to hydroxyurea is attested by the significant changes in some biological parameters. The limits of this study are the small size of our single center cohort and the exclusion of patients not recorded in the Belgian Registry because of lack of parental consent. This last point might create a bias by selecting patients whose parents are more prone to participate actively in the comprehensive care program. This periodic evaluation is essential to ensure the quality of care of patients and to measure possible changes in the management. Comprehensive care developed in our tertiary center had been already effective since 2000. Physicians not only tend to prescribe more hydroxyurea in young symptomatic patients, but also routinely adjust the dose to reach the maximal tolerated dose. Moreover adherence to treatment has been achieved through continuous education. Disclosures No relevant conflicts of interest to declare.

Description: Chronic transfusion in sickle cell disease (SCD) remains the gold standard therapy for primary and secondary stroke prevention and is indicated for patients with recurrent severe vaso occlusive crisis (VOC) or acute chest syndrome (ACS). Automatized apheresis (AA) has several advantages compared to manual exchange transfusion (MET): shorter procedure, continuous control of fluid balance, etc. The aim of our study was to assess the safety and efficacy of AA in SCD patients previously treated with MET at Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium and to evaluate the change of the costs related to transfusion and chelation overtime. From January 2012, the AA program for SCD patients started in our institution. Patients on chronic transfusion program (CTP) and previously treated with MET were eligible to switch to AA if sufficient peripheral venous access to allow AA without the use of central venous line and if weight ≥ 30kg. On CTP, target HbS was

Description: The six-minute walk test (6MWT) was introduced in adults and children suffering from pulmonary or cardio-vascular conditions to assess their sub-maximal functional exercise capacity. In sickle cell disease (SCD), a reduced 6-minute walk distance was observed in adults with chronic pain, hip avascular necrosis and osteopenia ; and in children with low hemoglobin level, low fetal hemoglobin, a baseline elevated TRV. In a previous study (Dedeken et al., PLoS One 2014), we also showed that abnormal 6MWT was significantly associated with the presence of silent infarct. The aim of our study is to explore the evaluation of the 6MWT over time and to confirm the correlation with the cerebral vasculopathy in a larger cohort. This study was conducted at Hôpital Universitaire des Enfants Reine Fabiola (Brussels, Belgium) and included SCD children older than 6 years, regularly followed between 2011 and 2017 and who had at least two 6MWT. The age-standardized predicted value of the 6-minute walk distance (6MWD) was established as reported by Geiger. The 6MWT was considered as normal if the 6MWD was more than 80% of the age-standardized predicted value. Baseline hematological values, clinical events, cerebro-vascular disease, cardio-pulmonary parameters and disease-modifying treatment (DMT) were compared between those with normal and abnormal 6MWT and according to the 6MWD and between the 1st and the 2nd 6MWT overtime. 118 patients have been assessed twice and had at first evaluation a 6MWD of 90.6% (Range 49-119%), with an abnormal test found in 5.1%. The characteristics of the patients are detailed in the Table 1. The changes of the 6MWD and the biological data over time are detailed in Table 2. After 4 years of follow-up, 77.1% of patients were treated with Hydroxyurea (HU) and 16.6% patients were chronically transfused. In parallel with the increased HU prescribing rate, we have observed a significant increase of the Hb and the MCV and a decrease of reticulocytes and hemolysis parameters. The first 6WMT was performed at the median age of 10.3 years and the last one at the median age of 14.1 years. The median 6MWD increased over time including for non-chronically transfused patients. Girls performed less well in the 6MWT (93% for girls vs. 95.7% for boys; P = 0.03). Acute chest syndrome was significantly more frequent in boys (62%) compare to girls (38.7%). Nevertheless, no other differences were founded between boys and girls regarding biological values, clinical events or DMT. 26.5% of our patients have silent infarcts at a median age of 14.6 years. The 6MWD was the same in patients with and without silent infarcts (92.5% vs. 95% ; P=0.17) even when chronically transfused patients were excluded (94% vs. 95% ; P= 0.20). Patients with silent infarcts have a significant lower hemoglobin level and higher reticulocytes count, neutrophils count, LDH and MCV. In conclusion, the 6MWD observed in our cohort characterized by a very high rate of HU treatment is much higher than published in others series and improved over time. With only 5% of SCD patients having a 6MWD 〈 80% of the normal predicted value at last evaluation, we were not able anymore to confirm a correlation between the presence of silent infracts and abnormal 6MWT. Disclosures No relevant conflicts of interest to declare.