Sickle Cell Trait Research Articles

APOL1, Sickle Cell Trait, and CKD in the Jackson Heart Study

Rationale & ObjectiveApolipoprotein L1 (APOL1) high-risk variants are associated with an increased risk for chronic kidney disease (CKD) among African Americans. Less is known regarding the risk for the development of CKD and kidney failure (end-stage kidney disease [ESKD]) among African Americans with only 1 APOL1 risk variant or whether the risk is modified by sickle cell trait.Study DesignThe Jackson Heart Study is a community-based longitudinal cohort study.Setting & ParticipantsSelf-reported African Americans in the Jackson Heart Study (n = 5,306).ExposuresAPOL1 G1 and G2 genotypes and sickle cell trait.OutcomesIncident CKD (estimated glomerular filtration rate < 60 mL/min/1.73 m2), albuminuria (urinary albumin-creatinine ratio ≥ 30 mg/g), continuous and rapid kidney function decline (≥30% decline), and incident ESKD.Analytical ApproachMultivariable linear and logistic regression, and Cox proportional hazards models adjusted for age, sex, hypertension, diabetes, ancestry informative markers, and sickle cell trait.ResultsOf 2,300 participants, 41.3% had zero, 45.1% had 1, and 13.6% had 2 APOL1 risk variants. Sickle cell trait was present in 8.5%. Compared with participants with zero APOL1 risk variants, those with 2 alleles had an increased risk for incident albuminuria (adjusted HR [aHR], 1.88; 95% CI, 1.04 to 3.40), ESKD (aHR, 9.05; 95% CI, 1.79 to 45.85), incident CKD (aHR, 1.65; 95% CI, 1.06 to 2.57), continuous decline (β = −1.90; 95% CI, −3.35 to −0.45), and rapid kidney function decline (OR, 2.21; 95% CI, 1.22 to 4.00) after adjustment for sickle cell trait, with similar results after adjustment for ancestry informative markers. Having 1 APOL1 risk variant was not associated with CKD outcomes and there was no interaction of APOL1 with sickle cell trait.LimitationsSingle-site recruitment of African American individuals with APOL1 and sickle cell trait.ConclusionsThe presence of 1 APOL1 risk allele was not associated with increased risk for CKD outcomes, whereas 2 risk alleles were associated with incident albuminuria, CKD, ESKD, and rapid and continuous kidney function decline. Additional studies are needed to determine factors that might alter the risk for adverse kidney outcomes among individuals with high-risk APOL1 genotypes.

Haplotype-resolved germline and somatic alterations in renal medullary carcinomas

BackgroundRenal medullary carcinomas (RMCs) are rare kidney cancers that occur in adolescents and young adults of African ancestry. Although RMC is associated with the sickle cell trait and somatic loss of the tumor suppressor, SMARCB1, the ancestral origins of RMC remain unknown. Further, characterization of structural variants (SVs) involving SMARCB1 in RMC remains limited.MethodsWe used linked-read genome sequencing to reconstruct germline and somatic haplotypes in 15 unrelated patients with RMC registered on the Children’s Oncology Group (COG) AREN03B2 study between 2006 and 2017 or from our prior study. We performed fine-mapping of the HBB locus and assessed the germline for cancer predisposition genes. Subsequently, we assessed the tumor samples for mutations outside of SMARCB1 and integrated RNA sequencing to interrogate the structural variants at the SMARCB1 locus.ResultsWe find that the haplotype of the sickle cell mutation in patients with RMC originated from three geographical regions in Africa. In addition, fine-mapping of the HBB locus identified the sickle cell mutation as the sole candidate variant. We further identify that the SMARCB1 structural variants are characterized by blunt or 1-bp homology events.ConclusionsOur findings suggest that RMC does not arise from a single founder population and that the HbS allele is a strong candidate germline allele which confers risk for RMC. Furthermore, we find that the SVs that disrupt SMARCB1 function are likely repaired by non-homologous end-joining. These findings highlight how haplotype-based analyses using linked-read genome sequencing can be applied to identify potential risk variants in small and rare disease cohorts and provide nucleotide resolution to structural variants.

Splenic infarction in sickle cell trait: A comprehensive systematic review of case studies.

Sickle cell trait (SCT), a commonly asymptomatic condition, has many associated clinical complications that upon presentation, can be very difficult to attribute to SCT. The effects of SCT on the spleen, for example, are not completely understood, though there have been a number of case reports detailing related complications in diverse populations. Our objective was to perform the first comprehensive case report review of splenic infarction in SCT patients to highlight the relevance of this seemingly rare condition. We conducted an extensive literature search reviewing case reports and case series of acute splenic infarctions from 1970 to 2020. This comprehensive search resulted in 54 articles with a total of 85 individuals. The ages ranged from 7 to 65, 12% were female. Individuals were of African‐American (26%), European (16%), South Asian (13%), Middle Eastern (7%), Latin American (7%), North or East African (4%), Mediterranean (4%), West African (1%), and unknown (22%) origins. Although splenic infarct in SCT patients has been associated with high altitudes, 39% of cases reporting altitude occurred below 3000 m. Among cases where HbS values were recorded, 88% occurred in individuals with HbS levels higher than 35%, suggesting that high HbS values may be a risk factor for splenic infarction. Our findings indicate that splenic infarct occurs across a wide range of demographic populations and environmental settings. While our understanding of SCT evolves, the findings here suggest that future advances in research and healthcare could benefit more from real‐time surveillance and registry initiation for various SCT outcomes such as splenic infarct.

Epidemiology and disease burden of sickle cell disease in France: A descriptive study based on a French nationwide claim database.

Sickle cell disease (SCD) is a severe hematological disorder. The most common acute complication of SCD is vaso-occlusive crisis (VOC), but SCD is a systemic disease potentially involving all organs. SCD prevalence estimates rely mostly on extrapolations from incidence-based newborn screening programs, although recent improvements in survival may have led to an increase in prevalence, and immigration could account for a substantial number of prevalent patients in Europe. The primary objective of this study was to estimate SCD prevalence in France. A cross-sectional observational study was conducted using a representative sample of national health insurance data. SCD patients followed up in France between 2006 and 2011 were captured through hydroxyurea reimbursement and with the International Classification of Diseases (ICD-10) SCD specific code D570.1.2, excluding code D573 (which corresponds to sickle cell trait (SCT)). Nevertheless, we assumed that ICD-10 diagnosis coding for inpatient stays could be imperfect, with the possibility of SCT being miscoded as SCD. Therefore, prevalence was analyzed in two groups of patients [with at least one (G1) or two (G2) inpatient stay] based on the number of SCD-related inpatient stays in the six-year study period, assuming that SCT patients are rarely rehospitalized compared to SCD. The prevalence of SCD in the sample, which was considered to be representative of the French population, was then extrapolated to the general population. The rate of vaso-occlusive crisis (VOC) events was estimated based on hospitalizations, emergencies, opioid reimbursements, transfusions, and sick leave. Based on the number of patients identified for G1 and G2, the 2016 French prevalence was estimated to be between 48.6 per 100,000 (G1) or 32,400 patients and 29.7 per 100,000 (G2) or 19,800 patients. An average of 1.51 VOC events per year were identified, with an increase frequency of 15 to 24 years of age. The average annual number of hospitalizations was between 0.70 (G1) and 1.11 (G2) per patient. Intensive care was observed in 7.6% of VOC-related hospitalizations. Fewer than 34% of SCD patients in our sample received hydroxyurea at any point in their follow-up. The annual average cost of SCD care is €5,528.70 (G1) to €6,643.80 (G2), with most costs arising from hospitalization and lab testing. Our study estimates SCD prevalence in France at between 19,800 and 32,400 patients in 2016, higher than previously published. This study highlights the significant disease burden associated with vaso-occlusive events.

Community based screening for sickle haemoglobin among pregnant women in Benue State, Nigeria: I-Care-to-Know, a Healthy Beginning Initiative

BackgroundHaemoglobin genotype screening at prenatal care offers women an opportunity to be aware of their genotype, receive education on sickle cell disease (SCD) and may increase maternal demand for SCD newborn screening. In developed countries, most pregnant women who access prenatal care and deliver at the hospital receive haemoglobin genotype screening. In settings with low prenatal care attendance and low hospital deliveries, community-based screening may provide similar opportunity for pregnant women. We assessed the feasibility and acceptability of integrating haemoglobin genotype screening into an existing community-based HIV program.MethodsOnsite community-based integrated testing for HIV, hepatitis B virus and haemoglobin electrophoresis, were conducted for pregnant women and their male partners. Community Health Advisors implementing the NIH and PEPFAR-supported Healthy Beginning Initiative (HBI) program provided education on SCD, collected blood sample for haemoglobin electrophoresis and provided test results to participants enrolled into the HBI program. We concurrently conducted a cross-sectional study using a pretested, semi-structured, interviewer administered questionnaire to collect demographic data and assess awareness of individual haemoglobin “genotype” among HBI pregnant women participants.ResultsIn this study, 99.9% (10,167/10,168) of pregnant women who received education on SCD accepted and completed the survey, had blood drawn for haemoglobin electrophoresis and received their results. A majority of participating pregnant women (97.0%) were not aware of their haemoglobin “genotype”. Among the participants who were incorrect about their haemoglobin “genotype”, 41.1% (23/56) of women who reported their haemoglobin “genotype” as AA were actually AS. The odds of haemoglobin “genotype” awareness was higher among participants who were in younger age group, completed tertiary education, had less number of pregnancies, and attended antenatal care. Overall prevalence of sickle cell trait (AS) was 18.7%.ConclusionsIt is feasible to integrate haemoglobin “genotype” testing into an existing community-based maternal-child program. Most pregnant women who were unaware of their haemoglobin “genotype” accepted and had haemoglobin genotype testing, and received their test results. Increasing parental awareness of their own haemoglobin “genotype” could increase their likelihood of accepting newborn screening for SCD.

IVS-II-16 (G>C) (HBB: c.315+16G>C) or IVS-II-666 (C>T) (HBB: c.316-185C>T) Mutations Trigger an Hb S (HBB: c.20A>T)/β+-Thalassemia Phenotype in an Hb S Trait Patient

Sickle cell trait is a medical condition caused by the presence of both mutant Hb S (HBB: c.20A>T) and normal Hb A alleles. Although sickle cell trait is typically considered to be asymptomatic and benign, genetic modifiers and mutations can lead to severe clinical complications. In this study, the possible pathogenicity of the IVS-II-16 (G>C) (HBB: c.315+16G>C) and IVS-II-666 (C>T) (HBB: c.316-185C>T) mutations, which are considered to be neutral polymorphisms, and the association between the Hb S mutation are presented. To the best of our knowledge, these polymorphisms have not been previously reported in any sickle cell trait patient, and no relevant studies have been conducted. We recently studied a 40-year-old woman (proband), diagnosed to be an Hb S/β-thalassemia (β-thal) carrier. β-Globin mutations were analyzed using a DNA sequencer based on the Sanger method. The HbVar and ClinVar databases show IVS-II-16 and IVS-II-666 to be intronic mutations. However, statements in these data banks contradict our findings. In the present study, a transfusion-dependent Hb S patient, behaving as an Hb S/β-thal case due to these mutations, was reported. These mutations have not been previously reported in an Hb S patient. Although the IVS-II-16 and IVS-II-666 mutations were previously reported as benign, they converted the Hb S phenotype to transfusion-dependent Hb S/β-thal when combined with Hb S. In this regard, IVS-II-16 and IVS-II-666 mutations may not be innocent, as previously thought.

Abstract 1247: Targeting neddylation in combination with cytotoxic chemotherapy for the treatment of renal medullary carcinoma

Abstract Renal medullary carcinoma (RMC) is a rare and highly aggressive malignancy that affects primarily young patients of African descent with sickle cell trait. No targeted therapies are currently approved for patients with RMC and the median survival from diagnosis is only 13 months with the current standard of care therapy consisting of platinum-based cytotoxic chemotherapy. New therapeutic targets are urgently needed for this lethal disease. We previously identified proteotoxic and replication stress as hallmarks of RMC (Carugo et al. Cancer Cell, 2019; Msaouel et al. Cancer Cell, 2020). The neddylation pathway is a critical regulator that protects cells from proteotoxic and replication stress. We therefore hypothesized that inhibition of neddylation will produce antitumor responses in RMC. We accordingly tested the efficacy of the neddylation activating enzyme inhibitor pevonedistat (MLN4924) in vitro in the platinum-naïve RMC2C and the platinum-experienced RMC219 cell lines, as well as in vivo in the platinum-naïve RMC2X and the platinum-experienced RMC32X patient-derived xenograft (PDX) models. Cell viability was evaluated using MTT assays. To determine the effects of pevonedistat in combination with platinum-based cytotoxic chemotherapy (carboplatin + paclitaxel) in vivo, immunodeficient mice bearing subcutaneous RMC tumors were divided into 4 treatment arms (n=5-8 per arm) which consisted of vehicle control, pevonedistat (30mg/kg), carboplatin (80mg/kg) + paclitaxel (20mg/kg), and pevonedistat+carboplatin+paclitaxel. Synergy between pevonedistat and chemotherapy was determined based on the Bliss definition of drug independence. Pevonedistat showed potent in vitro antitumor efficacy against both RMC2C (IC50 0.199 μΜ) and RMC219 (IC50 0.551) cell lines. In the RMC2X in vivo model, mean tumor volumes were 2164±835mm3 for control, 433±250mm3 for pevonedistat, 339±44mm3 for chemotherapy, 75±46mm3 for pevonedistat + chemotherapy. The combination of pevonedistat with chemotherapy significantly reduced tumor volumes compared to vehicle control (p=0.02) and chemotherapy alone (p=0.008). A similar pattern was demonstrated with RMC32X tumor volumes, whereby pevonedistat combined with chemotherapy again significantly reduced tumor volume compared to control (p=0.006) and chemotherapy alone (p=0.02). A significant synergistic therapeutic effect of pevonedistat combined with chemotherapy was found for both RMC2X (p=0.008) and RMC32X (p=0.002). Our results identify the neddylation pathway as a targetable vulnerability of RMC tumors, and provide in vitro and in vivo preclinical rationale for a clinical trial testing the combination of pevonedistat with carboplatin + paclitaxel to improve the outcomes of patients with this deadly malignancy. Citation Format: Daniel D. Shapiro, Niki Millward Zacharias, Durga N. Tripathi, Jean-Philippe Bertocchio, Melinda Soeung, Priya Rao, Cheryl L. Walker, Giannicola Genovese, Nizar M. Tannir, Christopher G. Wood, Jose A. Karam, Pavlos Msaouel. Targeting neddylation in combination with cytotoxic chemotherapy for the treatment of renal medullary carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1247.

Unexpected Detection of Abnormal Hemoglobin Variants During Routine HbA1c Analysis by HPLC Technique: Challenges and Opportunities in HbA1c Testing

Background: Glycated Hemoglobin A1c (HbA1c) assay is most widely used in diabetic patients for assessing long-term control of glycemia. The presence of hemoglobin variants may be an incidental finding and can interfere with HbA1c measurements. The aim of the present study is to investigate the prevalence and impact of interference of different abnormal hemoglobin variants on HbA1c measurements during routine HbA1c testing. Methods: A total of 12,092 HbA1c samples were collected from January to August 2018. HbA1c quantification was carried out on a Variant II Bio-Rad’s HPLC analyzer. Abnormal chromatograms were further analyzed using the extended-run high-pressure liquid chromatography (HPLC) analysis in the A2/F mode. Results: The samples were examined for presence of abnormal variants. Samples producing abnormal chromatograms were further analyzed in A2/F mode to characterize hemoglobin variants. Abnormal variants were identified in 126 (1%) samples, and 74 (0.59%) sickle cell traits (SCT) were the most common variant in our findings. Moreover, 30 (0.24%) cases were eluted in the variant window in A1c mode, which on further analysis were found to be Hb E &amp; Hb D traits. Furthermore, 3 (0.02%) cases were eluted at a RT &lt;1 min as (unknown) and identified as Hb H. Also,19 (0.15%) samples were eluted in the P3 window at different retention times. Conclusion: Observing each chromatograph after the analysis can help us in identifying silent hemoglobin variants in routine HbA1c testing. Knowledge and awareness of common hemoglobin variants affecting measurement of HbA1c is imperative to avoid reporting of falsely low HbA1c values in diabetic population.

Prospective Newborn Screening for Sickle Cell Disease and Other Inherited Blood Disorders in Central Malawi.

Objectives: Newborn screening in the United States and Europe allows early identification of congenital disorders but does not yet exist in most low-resource settings, especially in sub-Saharan Africa. Newborn screening can identify multiple inherited hematological disorders, but feasibility and effectiveness for Africa are not fully determined. Methods: Surplus dried blood spot collected in Central Malawi through the HIV Early Infant Diagnosis surveillance program were repurposed and tested by isoelectric focusing for sickle cell disease and trait. Additional genetic testing identified G6PD deficiency and alpha thalassemia. Results: Testing of 10,529 cards revealed an overall sickle cell trait prevalence of 7.0% (range 3.9–9.7% by district); 10 of 14 infants identified with sickle cell disease (prevalence 0.1%) were located and received care at a specialized clinic. Subsequent testing of 1,329 randomly selected cards identified alpha thalassemia trait in 45.7% of samples, and G6PD deficiency in 20.4% of males and 3.4% of females, with 29.0% of females as heterozygous carriers. Conclusion: Inherited hematological disorders are common in Central Malawi; early identification through newborn screening can improve clinical outcomes and should be supported throughout Africa.

Splenic Infarct As an Harbinger for Sickle Cell Traits in High Altitude

Background: Sickle cell trait (SCT) is a common genetic abnormality in the so called ‘Sickle belts’ in India. Splenic infarction often brings to medical attention an underlying SCT, when appropriately looked for. The hypoxic environment of high-altitude area (HAA) is conducive for developing a splenic infarct in an SCT individual. Soldiers get frequently exposed to extreme altitudes.Aim & Objective: The objectives of the study were (a) To identify the incidence and etiology of splenic infarcts in HAA. (b) To identify the predisposing factors for splenic infarct with sickle cell trait from all patients managed at a tertiary care hospital at sea level.Methodology: The study was done in two phases. Phase I of the study was conducted at an high altitude (HA) secondary care hospital. All patients admitted with splenic infarct (n-82) to this hospital over a period of 1.5y were evaluated for limited thrombophilia states (FVL mutation, PNH, Polycythemia, MTHFR mutation, JAK2 mutation) and sickle cell trait. Also, these patients were evaluated for portal vein thrombosis or concomitant thrombosis of any other sites. Phase II of the study was conducted at a tertiary care referral center of the armed forces, where all the patients with concomitant sickle cell trait and splenic infarct were evaluated for precipitating causes over a period of 04y (n-51).Results: A total of 82 patients were admitted with splenic infarct to the HA secondary care hospital during the study period. The median age of the population was 28.4y (range: 23-42y) and all were males. They constituted 38.31% of all cases of thrombosis (214) admissions at HA in the given study period. They were second only to DVT (112, 52.33%) in the incidence of HA associated thrombosis, which were followed by CVT (16, 7.47%) and PTE (14, 6.54%) (Patients had variable combinations of DVT/ PTE/ CVT/ Splenic infarcts). Patients of splenic infarcts initially presented to surgeon in 85.3% instances (n-70) with pain abdomen (88%, n-72) or pleuritic pain (33%, n-27). Concurrent thrombosis at other sites were present in 33% (n-27) of the patients, of which 25.6% (n-21) had thrombosis of spleno-portal axis. High altitude illnesses were present in only 7.3% (n-6) of the patients. The mean duration to occurrence of the splenic infarct was 124.2 days (SD-31.8) after arrival to HA, but was less than 5.4 days (SD - 2.1) in patients with sickle cell trait (p<0.01). The etiology was mostly idiopathic (64.6%, n-53) followed by sickle cell trait in 24.4% (n-20) and other thrombophilia states in 10.9% (n-9) cases. Among the secondary causes, sickle cell trait was the commonest cause. Among the idiopathic cases few might have been secondary to protein C/ S or Antithrombin III deficiency which could not be evaluated during the acute phase. In patients with sickle cell trait, sickling at the time of splenic infarct at HA was seen in only 55% (n-11) though expected to be 100%. Family history was present in only 5% (n-1) of the patients with sickle cell trait of any sickling syndrome.In phase II of the study, a total of 51 cases of sickle cell trait with splenic infarcts were admitted in the study period, who were evaluated. The median age of the study population was 29.6y (range: 21-48y). Of these, 82.4% (n-42) patients had developed the splenic infarct on exposure to HAA. Clinically splenomegaly was seen in 25.5% (n-13) patients with splenic infarct at presentation. The mean HbS was 37.34% in the SCT patients. A thrombus in the spleno-portal axis was demonstrated in 17.6% (n-9) of cases. The splenic rupture was a rare event, seen in only one patient. Splenectomy was done in only one patient due to non-resolving abscess. Of these patients 09 patients had sickle cell syndrome on exposure to severe exertion (n-8) / fever (n-1) at plains.Conclusion: It is important to test for sickle cell trait in these otherwise healthy soldiers who develop splenic infarct at HA. The clinical importance of otherwise benign sickle cell trait in the form of splenic infarct by HA exposure or severe exertion is elucidated by this study. DisclosuresNo relevant conflicts of interest to declare.

Sickle Cell Trait and Cognitive Function in African Americans: The Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort

▪Background: Sickle cell anemia (SCA) has been associated with cognitive dysfunction. Increasing evidence suggests that some complications of SCA, such as kidney disease and venous thromboembolism, also affect those with sickle cell trait (SCT). Thus, SCT may not be a benign condition. Based on these findings, we hypothesized that SCT is a risk factor for cognitive function in African-Americans. We previously reported no association of SCT with cognitive impairment evaluated by a global screening test. Here we studied specific cognitive function measures.Methods: We studied African-American adults aged 45 and older from a national prospective cohort study of 30,239 white and black Americans; the REGARDS study. Participants were enrolled in 2003-7 and followed for up to 10 years. We collected extensive baseline risk factor data, and administered a cognitive battery every 2 years including tests of learning and memory (Word List Learning (WLL), Word List Recall (WLR)), semantic fluency by the Animal Naming test, and phonemic fluency by the Letter F test. WLL is the sum of words learned over 3 trials of immediate recall of 10 words (score ranges 0-30 words). WLR is the sum of words recalled after intervening questions (range 0-10 words). The Animal Naming score is the number of animals a participant can name within 1-minute and the Letter F score is the number of words beginning with the letter F that a participant can say within 1-minute. Participants included in this analysis were African-Americans without SCA or prebaseline stroke, who had SCT genotyping. Participants with baseline cognitive impairment by a global screening test were excluded. Mixed models were employed to assess the association of SCT with repeated measures of each test, adjusted for risk factors. Censoring occurred at the time of a stroke, death or withdrawal from the study.Results: There were 7,078 participants with at least 1 assessment of WLL and WLR who met inclusion criteria; their mean age was 63.4 years, 64% were women, and 517 had SCT. Those with SCT were more likely than those without to have hypertension (65% vs 60%; p=0.04), no alcohol use (75% vs 70%, p=0.03), and lower estimated glomerular filtration rate (eGFR) (86 vs 90 ml/min/1.73m2; p<0.0001). They were similar on other factors. The top panel of the figure shows that WLL and WLR changed little over time and there was no difference in scores by SCT status (adjusted p values shown). There were 7,296 participants included in the Animal Naming analysis and 5,946 for Letter F (differences due to delays in processing scores). The lower panel of the figure shows that performance on both tests worsened over time, with no difference by SCT status (adjusted p values shown).Conclusion: In this prospectively followed general population cohort of middle-aged and older African-Americans with longitudinal cognitive function testing, SCT was not associated with differences in cognitive functioning.Figure. Sickle Cell Trait and Longitudinal Change in Cognitive Doman MeasuresDashed lines represent those with sickle cell trait and solid lines those without sickle cell trait. Models were adjusted for age, sex, education, income, region of residence, alcohol use, smoking status, exercise, history of heart disease, hypertension, systolic blood pressure, left ventricular hypertrophy by ECG, hyperlipidemia, albumin-creatinine ratio, estimated glomerular filtration rate, statin use, diabetes and atrial fibrillation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

A Pilot Study of Sickle Cell Anemia in the Belizean Population

Background: Sickle Cell Anemia (Sickle Cell Disease) is an inherited disease resulting from a genetic mutation in the hemoglobin protein found in red blood cells. Screening is a requirement in the United States and in U.S. territories, and is considered a component of routine prenatal care. In resource limited countries such as Belize, there are no screening programs in place for testing newborns for Sickle Cell Anemia, and the disease is largely undefined. Children often go undiagnosed until they exhibit clinical symptoms. Untreated Sickle Cell Anemia in children under the age of 5 can lead to poor clinical outcomes. Oftentimes, those suspected of having the disease obtain diagnostic testing from a foreign country, and the test frequently used is the Sickle Prep Test. While the Sickle Prep Test is able to identify the presence of hemoglobin mutations, it cannot differentiate between sickle cell disease and sickle cell trait, a distinction which has profound clinical implications. A new technology, the Sickle SCAN test, utilizes a chromatographic, immunologic approach to qualitatively identify the presence of select variants of the hemoglobin protein (HbS, HbA, HbC), thereby allowing clinicians to differentiate between sickle cell disease and sickle cell trait. This test is a powerful tool that it is cost effective and timely; it does not require complicated testing equipment, and can disclose one's hemoglobin genetic profile in under 6 minutes. Methods: 87 patients were enrolled and tested for sickle cell disease and sickle cell trait in the towns of Dangriga and Hopkins, Belize. Testing took place over the course of 4 days. A survey was administered to collect key demographic information and information regarding participant's knowledge about Sickle Cell Anemia, past diagnosis, and family history of disease. Results: 13% were found to have sickle cell disease (n=12), and 25% were found to have the trait (n=22). For those with the disease or trait, the majority were found to belong to the Garifuna ethnic group. 26% of the participants had no knowledge of Sickle Cell Anemia. It was also reported that 51% had a family member with the disease, and 23% were unsure whether a family member had the disease.Conclusions: This pilot study demonstrates the feasibility ofusing the Sickle SCAN test to gather knowledge about the prevalence of Sickle Cell Anemia in a population where the disease remains largely undocumented. DisclosuresNo relevant conflicts of interest to declare.

Epidemiologic Characterization of Transfusion Recipients with Red Blood Cell Alloantibodies from Four US Regions: Evidence from the REDS-III Recipient Database

Introduction: Red blood cell (RBC) alloimmunization is one of the most common complications of RBC transfusion. Despite the fact that alloimmunization impacts many transfusion recipients, the lack of standardized alloimmunization registries in the US has prevented large studies from being completed. Through the development of a uniform electronic research database, we investigated alloimmunization rates and diagnoses in inpatients and outpatients across the US.Methods: The REDS-III recipient database, established in 2013, houses demographic, diagnostic, transfusion, laboratory, and other information on inpatients and outpatients at 12 hospitals in 4 geographic regions. For this study, an antibody “responder” (R) was defined as an individual who had a putative transfusion (or pregnancy)-associated red cell antibody identified by screen at any point during the study period, independent of documented RBC exposure or pregnancy during the study period. An antibody “non-responder” (NR) was defined as an individual who was transfused with at least one unit of RBCs during the study period, and had a negative antibody screen at least 15 days post-transfusion. Anti-D antibodies were excluded from studied females, given an inability to distinguish passively administered anti-D in the database from authentic alloantibodies. Demographics, blood type, ICD9/10 codes, and antibody screen results were compared for R and NRs. Odds ratios were calculated for the likelihood of being a R or NR, based on the presence or absence of select chronic disease states.Results: 612,417 patients were recorded in the REDS recipient database from 2013-2016. 318,918 unique patients in the database had an RBC antibody screen during the study period. Of these, 6597 had at least one transfusion-associated RBC alloantibody identified by routine antibody screen (overall alloimmunization rate among all screened patients independent of RBC exposure = 2.07%). 63.8% of the R were female (alloimmunization rate 2.97%) and 36.2% were male (alloimmunization rate 1.35%). 30,468 unique patients (49.8% female and 50.2% male) were NR; the mean RBC exposure during the study period was similar between R and NR (mean, s.d., and median of 8.8, 18.2, and 4 units versus 9.3, 14.3, and 5 units). Approximately 60-70% of the antibodies in R were pre-existing, and the remainder were generated during the study period. Few children under 10 years of age were R compared to older age groups; an equation of R/R+NR = 26/26 + 467 = 5.3%. There were no differences in R vs NR by A/B/O blood type, though Rh negative patients (R/R+NR of 1175/1175 + 3901 = 23.1%) were significantly more likely to be R than Rh positive patients (R/R + NR of 5365/5365 + 26544 = 16.8%). .A total of 8892 clinically significant antibodies were detected, including 4749 (53.4%) in the Rh family (2588 anti-E, 780 anti-C, 556 anti-c, 105 anti-e, 525 anti-D), 1937 (21.8%) in the K family, 912 (10.3%) in the Kidd family, and 669 (7.5%) in the Duffy family, among others. Patients with sickle cell disease (n=554, OR 2.6, p<0.0001), sickle cell trait (n=117, OR 1.8, p=0.02), 'coronary atherosclerosis or heart disease (n=12,403, OR 1.2, p<0.0001), lupus (n=969, OR 1.3, p=0.002), rheumatoid arthritis (n=1213, OR 1.2, p=0.01), and myelodysplastic syndrome (n=1162, OR 1.3, p=0.0008) were more likely to be R than NR. In contrast, patients with leukemia (n=2801, OR 0.5, p<0.0001), solid tumors (n=17,513, OR 0.6, p<0.0001), and solid organ transplant (n=1491, OR 0.7, p=0.0001) were less likely to be R than NR.Conclusions: Data collected in this multi-center recipient database provide the largest RBC alloimmunized patient cohort ever studied in the US. The 2.07% overall rate of alloimmunization is similar to that reported in other retrospective studies, with females having higher alloimmunization rates than males. Rh negative individuals were significantly more likely to be alloimmunized than Rh positive patients, despite the exclusion of anti-D antibodies in females. Other unexpected findings include the predisposition to alloimmunization observed in patients with sickle cell trait and coronary artery disease. Ongoing studies are investigating the timing of RBC exposure to new antibody formation in this patient cohort, as well as potential physiologic explanations for the chronic disease associated findings. DisclosuresNo relevant conflicts of interest to declare.

Spectrum of Hematological Disorders in Young Navy Recruits

Introduction:Hematological disorders can vary from simple anemias to complicated malignancies. The aim of our study was to identify the spectrum of hematological disorders in young navy recruits that prompted a hematology oncology consult. We also aimed to obtain a sense of the recruitment process, screening tests performed and help prevent medical-hematological emergencies.Materials and Methods:A retrospective chart review was conducted at our hospital, Captain James a Lovell Federal Health Care Centre, North Chicago. Recruits who were referred to hematology and oncology clinic in the past one year(2015-2016) were included.Results:We reviewed a total of 122 patients, which included 84 males and 38 female recruits. The age range was 18 to 31. The most common reason for consult was microcytic anemia evaluation (30%), followed by normocytic anemia (21%) and coagulopathy evaluation (13%). Other reasons for consult included neutropenia, leukocytosis, microcytic anemia with neutropenia, normocytic anemia with neutropenia, thrombocytopenia, thrombocytosis, pancytopenia, splenomegaly, pancytopenia in association with splenomegaly, recurrent epistaxis, unusual bleeding, history of deep vein thrombosis and testicular tumor (Table 1).Microcytic anemia was secondary to Iron deficiency anemia(IDA) in 59% of recruits, either due to malnutrition and menorrhagia in females or gastritis with blood loss in males. Other causes of microcytic anemia were E-Alpha thalassemia, alpha thalassemia minima alone or in combination with IDA, beta thalassemia trait, sickle cell trait in association with IDA and alpha thalassemia minima. The most common cause of normocytic anemia was Anemia of Chronic disease in association with Vitamin D deficiency (15%). Other causes are mentioned in table 1. Coagulopathy was mostly secondary to viral syndrome causing abnormal liver function tests/LFT (75%). Coagulopathy due to mild hemophilia was identified in 3 patients. Thrombocytopenia occurred because of ITP (Immune Thrombocytopenia) or viral syndrome in most patients.Navy recruits are routinely screened for sickle cell disease and G6PD deficiency, but are not screened for anemia or coagulation abnormalities. Most recruits in our study presented with severe anemia or bleeding after dental extraction (especially hemophiliacs and thrombocytopenic patients) which disrupted recruit training. Few recruits were also separated depending on severity of hematological illness. In our retrospective study, even mild hemophiliacs had abnormal PTT. Hence, if complete blood count(CBC) and prothrombin time/partial thromboplastin time (PT/PTT) testing were included as a part of screening during recruit enrollment, many hematological disorders can be diagnosed early and complications can be prevented. Early diagnosis will also help identify recruits with severe and disabling hematological disorders, thereby preventing their admission to boot camp and avoiding unnecessary training expense. Good testicular exam is also recommended as part of initial screening as one of our patients was diagnosed with testicular tumor.Conclusion:Young navy recruits are a unique group of people, many of whom have minimal medical and dental care because of poor socio-economic status at home. Demanding physical activity in presence of underlying anemia, or dental extraction in presence of bleeding disorders or platelet abnormalities cause medical-hematologic emergencies. Simple screening tests such as CBC, PT/PTT and testicular exam can help identify hematological disorders early and prevent complications. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Assessment of Referral Patterns of Adult Patients to a Sickle Cell Disease Specialty Clinic within a Statewide Sickle Cell Network

Background: Sickle cell disease (SCD) is the most common inherited blood disorder in the United States (U.S.). Despite advances in the treatment for children with SCD, care for affected adults has not significantly improved and is often inaccessible. Difficulties with access to care for adults with SCD in the US is multifactorial and includes paucity of trained, specialized physicians, limited physical access to specialty centers, lack of health insurance/health care coverage, and lack of SCD-education by other medical providers. To address these issues, we have established a state-wide sickle cell disease network to improve access to care for affect adults in South Carolina. This network, (SC)2, Sickle Cell-South Carolina is working to enhance access to care and to examine ongoing barriers to care for adults with SCD. The “hub” of (SC)2 is located at the Medical University of South Carolina (MUSC); specific outside hospitals have been identified as “spokes” within the state to form the network. Clinics are either established or being established at each spoke and additional education is being given through tele-mentoring. Current knowledge of referral patterns for patients with SCD is limited. Information on the mechanism of referral and the coordination of the referral process will ultimately help to eliminate obstacles to appropriate and timely patient referrals and help develop patient engagement.Methods: This is retrospective review of patients >18 years of age referred as “new patients” to the Lifespan Comprehensive Sickle Cell Center at MUSC from October 2015-July 2017. Patients were identified through a chart review of the (SC)2 database including referral notes, telephone calls, and initial patient visits. Data collected included the age of the individual, location (within the state) in which the individual resides, presence or absence of SCD, SCD phenotype, referral source, hematologic care within the prior two years, and the consistency of follow-up after the initial visit to the Sickle Cell Center.Results: During this period, 130 new adult patients were referred to the Lifespan Sickle Cell Center at MUSC. Patients referred for care ranged in age from 18-67 (median 34.5 years) of age and 33% (34/104) were male. To be included in the results, these individuals could not have been seen be the Lifespan Sickle Cell Center within the prior three years so that patients transitioned within the center were not included. Of those patients referred during this period, 85% percent (110/130) were successfully seen at the Lifespan Sickle Cell Center for (at least) an initial visit. However, 40% of these individuals missed their first new patient visit at the Sickle Cell Center and required additional outreach in order to complete that first visit. Of those patients successfully seen for a new patient visit, 95% were confirmed to have SCD (6 individuals were diagnosed with sickle cell trait or did not have a hemoglobinopathy). Only 1/3 of the patients referred to the Sickle Cell Center had seen a hematologist in the last 2 years. The majority of the remaining affected patients had not seen a hematologist since they were children or had never seen a hematologist in their lifetime. Referral sources included primary care physicians, subspecialists, (SC)2 affiliated hospitals (spokes), non-affiliated emergency departments, community based organizations and also included family members and peers. Most of the new referrals were from outside of the Tricounty (local) area (75%) and region did not affect the likelihood of successfully establishing care.Conclusion: The development of a statewide network (SC)2 is an effective initial strategy to facilitate referrals to a SCD center for adults with SCD. Physician-mediated engagement and outreach was key for introducing the (SC)2 network to the state and enabling referrals. When patients missed their initial new visit appointments, aggressive follow-up and trouble-shooting was key to ensuring a successful visit. Additional examination of patient-specific barriers at each phase of the referral process will be key to understanding discrepancies in follow-up rates and obstacles in the referral process. The process through which patients are referred to the center and arrive for their first visit are determinants in their future medical care. Enhanced implementation of this referral process is key to the success of the (SC)2 network. DisclosuresKanter:GBT: Research Funding; American Society of Hematology (Sickle Cell Disease Guideline Panel): Membership on an entity's Board of Directors or advisory committees; MUSC: Other: The site PI for sponsored research conducted at MUSC who receives funds from: Novartis, bluebird bio, GBT, Sancillo, Apopharma, Pfizer; Pfizer: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; NHLBI (sickle cell disease research advisory committee): Membership on an entity's Board of Directors or advisory committees, Research Funding; Apopharma: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sancillo: Research Funding.

A Study of Novel Beta Globin Mutation Associated with Dominant Beta-Thalassemia, Aberrant Erythroid Maturation and Differentiation Compounded with Hereditary Pyropoikilocytosis

Background: Heterozygosity for a beta-thalassemia mutation is clinically insignificant; however, microcytosis and mild anemia are oftenpresent. Rare mutations in the proximal half of the coding sequence for the beta globin gene (HBB) have been shown to cause an apparent autosomal dominant beta thalassemia that is associated with more severe anemia. These mutations often produce a frame shift in HBB mRNA; however, detection of the mutant transcript and/or protein has been controversial. In genotypically identical relatives, a milder phenotype can sometimes be observed, while others have severe anemia. It has been suggested that these phenotypic differences may be mediated by variations in destruction of mutant HBB transcripts by nonsense mediated decay .Materials: We studied a Dominican man with severe microcytic hypochromic anemia without iron deficiency, suggestive of thalassemia, and his family. We performed a detailed erythrocyte evaluation, including morphologic and hemoglobinopathy evaluations, globin sequencing, hemoglobin (Hb) stability evaluation, and band-3 testing for red blood cell (RBC) membrane abnormality, and analyzed DNA for mutations of genes encoding for RBC membrane proteins. We also performed in vitro expansion of erythroid progenitors, examined erythroid differentiation and proliferation, and searched for mutant HBB transcripts.Results: The propositus was found to have a novel beta-thalassemia mutation, HBB282delT encoding a Cys93fs (frame shift). He also had Heinz bodies and was positive for an unstable Hb (by isopropanol test), but had no electrophoretically detectable mutant Hb, and had absolute reticulocytopenia (Table). Peripheral blood had a typical hereditary pyropoikilocytosis (HPP) morphology (Figure 1), confirmed by band-3 testing. Family studies (Table) showed that the situation was more complex. His asymptomatic wife and one son had sickle cell trait (Table), and two other children inherited both the HBB282delT mutation and a Hb S mutation and were positive for band-3 deficiency testing. Their RBCs had typical HPP morphology, along with sickle cells (Figure 2), and had high HbF levels (Table). Reticulocytes were not available for detection of mutant transcripts by RNA analysis; we therefore performed in vitro expansion of erythroid progenitors in a 3-week liquid erythroid culture model (Gaikwad, et al, Exp Hemat, 2007). We detected mutant HBB282delT transcripts leading to a frameshift in exon 2, codon 93, where 9 new codons downstream from the mutation were encoded. The mutant transcript was present in equal amounts with the HBB transcript from the wild allele. Analysis of erythroid proliferation and differentiation revealed a marked decrease in proliferation (as determined by number of glycophorin-positive cells) and decreased differentiation (as evaluated by temporal changes of glycophorin and transferrin receptor positivity and intensity) in the propositus and two children with HBB 282delT. Hemoglobinization of their maturing erythroid progenitors was not discernible in 14-day cultures, in contrast to his wife, the asymptomatic son and the controls who had readily discernible hemoglobinized (red) progenitors. By day 21 of culture, he and the 2 affected children had only faintly hemoglobinized cells that appeared pink rather than red, and the erythroid progenitors of the propositus had minimal differentiation. None of the affected individuals had a SPTA1 exon 2 mutation, the most common missense mutations leading to the HPP phenotype.Discussion: We describe a novel HBB mutation associated with severe anemia, reticulocytopenia, and impaired erythropoiesis with delayed erythroid maturation and impaired hemoglobinization. The presented data suggest that the mutant protein is unstable and presumably toxic to erythroid progenitors. The mutant protein is not identifiable by routine hemoglobin studies and its presence will be evaluated by studies of precipitated hemoglobin (Heinz bodies and hemoglobin precipitates after isopropanol exposure). Effects of the mutant protein on maturation and differentiation can be assessed by RNAseq of erythroid progenitors compared to normal controls of the same stage of erythroid differentiation. The molecular basis of HPP is being evaluated by DNA sequencing of targeted genes encoding RBC membrane proteins and comparing their potential functional relevance to the HPP phenotype. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Allogeneic Blood and Marrow Transplantation for Pediatric Patients with Sickle Cell Anemia: An Institutional Experience

Introduction: Sickle cell anemia (SCA) is a genetic disease with potentially debilitating complications and shortened life-expectancy. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only cure for SCA, but is limited by the lack of available histocompatible sibling donors and transplant related morbidities. Alternative donor HSCT for SCA has been associated with variable outcomes. Methods: We conducted a retrospective review of all patients with SCA who underwent HSCT at our center between January 2014 and June 2017. Results: Table 1 shows the pre-HSCT characteristics of the study population (n=19). Candidates for HSCT were selected based on institutional and/or study eligibility criteria and were consented per the Declaration of Helsinki. The majority of patients were receiving chronic transfusions or hydroxyurea therapy. Two patients had concurrent autoimmune diseases and 79% had low 25-hydroxycholecalciferol levels (median 17.8 ng/ml). 9 patients (47.3%) received HLA-identical sibling transplants (MSD), 6 (31.5%) UD, and 4 (21%) α/β T cell depleted related haplo-identical (haplo) transplants. The median pre-HSCT comorbidity index (CI) was above 3 for patients receiving alternative donor transplants (>3 is associated with higher pre-HSCT acuity). HSCT characteristics are shown in Table 2. The majority of patients (68.4%) received bone marrow (BM), while 21% received mobilized peripheral blood stem cell (PBSC) grafts. All patients achieved initial high-level (>90%) donor chimerism. The median time to neutrophil engraftment (>500 cells/µL) was 14 days with significantly earlier engraftment seen among haplo recipients (median 10 days) compared to other graft sources (p < 0.02). The median time to platelet engraftment (>50,000 /µL) was 20 days. The median time to CD3+ T lymphocyte recovery (>200 cells/uL) was 195 days (range 20-384) (significantly earlier for the haplo group (figure 1a, p=0.01) and for CD19 (>66 cells/uL) was 104 (range 90-526) days post-HSCT (figure 1b). Secondary early graft rejection occurred in 2 patients who received haplo-identical HSCT, with sustained donor engraftment following a second transplant with the same donors in one of these patients. Overall incidence of > grade II (severe) acute graft versus host disease (GVHD) was 26%, with no significant difference observed among haplo recipients despite the absence of primary GVHD prophylaxis. Two UD recipients developed chronic GVHD (10.5% overall incidence). 11 (57%) patients (6 MSD, 3 UD, 2 haplo) developed CMV viremia, with one late onset disseminated CMV meningitis; 7 patients (36.8%) (3 MSD, 4 UD) developed adenoviremia; one patient developed HHV-6 viremia around the time of graft rejection. Both patients with concurrent autoimmune diseases did not experience significant post-HSCT complications. One patient with type I diabetes mellitus diagnosed 60 days prior to HSCT has had stable glycemic control. One patient with systemic lupus erythematous (SLE) remains in SLE remission post-HSCT. With a median follow-up of 568 (105-919) days, the overall 2-year survival was 84.2%. 88.8% for MSD, 83.3% for UD, and 75% (3 patients) survival for α/β T cell depleted haploidentical related HSCT (p=0.7) and a mean performance score of 90 among survivors. No adverse events were noted among donors with sickle cell trait, including 4 parent donors who received PBSC mobilization with either filgrastim and/or plerixafor. Conclusion: Alternative donor allogeneic HSCT should be considered for carefully selected patients with SCA. α/β T cell depleted related haplo-identical HSCT appears promising with low rates of severe acute GVHD in the absence of primary prophylaxis. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Blunted Cardiac Response to Head-up Tilt Occurs in Sickle Cell Disease but Not Healthy Controls

Introduction: Sickle cell disease (SCD) is characterized by microvascular occlusion from sickled red blood cells that can develop into full-blown vaso-occlusive crisis. We hypothesize that abnormal autonomic function plays a role in promoting microvascular occlusion in SCD. Head-up tilt (HUT) evokes a strong sympathetic response to the transient drop in blood pressure resulting from blood pooling in the lower extremities. Baroreflex regulation leads to heart rate (HR) increase and peripheral vasoconstriction. In this study, we subjected control and SCD subjects to the HUT test to assess their autonomic response.Objective: To evaluate the autonomic response and determine the relative contributions of the cardiac and peripheral vascular responses to HUT in SCD compared to control subjects.Experimental Protocols: 22 SCD and 17 control (healthy and sickle cell trait) subjects were recruited at Children's Hospital Los Angeles. Each subject laid supine on the tilt table for 5 minutes prior to being tilted up to 70° for 7 minutes, and subsequently returned to supine. Electrocardiogram, respiration, continuous blood pressure and photoplethysmograph (PPG) were measured continuously throughout the protocol. PPG amplitude was taken to represent peripheral blood flow (PBF) since reductions in PPG amplitude reflect vasoconstriction.Analysis: Mean systolic blood pressure (SBP), HR and PBF were calculated over 2 minutes under baseline and HUT conditions. In HUT, we analyzed the physiological responses following 3 minutes of stabilization. Heart rate variability indices: high frequency power (HFP) and low-to-high ratio (LHR), reflecting parasympathetic activity and sympatho-vagal balance respectively, were also computed. Percent change from baseline of all parameters were computed to assess the tilt response after adjusting for their baseline values.Results: There was not a significant change in SBP from baseline to HUT across all subjects. To maintain blood pressure, the response to HUT was categorized into 3 groups: 1) those who had increased HR (>15%) AND decreased PBF (>20%) from baseline, 2) those who only had increased HR, and 3) those who only had decreased PBF (Fig.1). While Group 1 and 2 responses were found in both controls and SCD, Group 3 responses consisted only of SCD subjects (Table 1). Although mean HR at baseline was not different from the other two groups, we found that HFP of Group 3 was lower compared to Group 1 (p = 0.0007) and Group 2 (p = 0.0396), while Group 3 LHR was higher than Group 1 (p = 0.0020).Discussion & Conclusions: HUT is standard and well-recognized assessment of the autonomic response to transient drop in blood pressure. While most subjects maintained their SBP by increasing both HR and peripheral resistance, a subset of SCD subjects responded to HUT via only peripheral vasoconstriction. Moreover, these SCD subjects had significantly lower parasympathetic HR modulation at baseline as reflected by lower HFP and higher LHR, an index of sympatho-vagal balance. The findings suggest that baroreflex control of heart rate during HUT in this subset of SCD subjects was blunted due to low vagal and high cardiac sympathetic tone, whereas baroreflex control of peripheral vascular resistance remained relatively intact. These data provide further evidence that there is significant autonomic dysfunction in some patients with SCD. This hypersensitivity to vasoconstriction would decrease microvascular flow and would likely lead to vaso-occlusion. We speculate that this subset of SCD subjects may also be the most vulnerable to reduced PBF and thus VOC during orthostatic stress. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Low Body Mass Index in Pregnant Women with Sickle Cell Disease Is Associated with Premature Delivery in Sub- Saharan Africa

Low Body Mass Index in Pregnant Women with Sickle Cell Disease Is Associated with Premature Delivery in Sub- Saharan Africa

Alemtuzumab/Low Dose TBI Conditioning Facilitates Stable Long-Term Donor Hematopoietic Cell Engraftment from Sibling Donors in Children with Sickle Cell Disease

BackgroundHematopoietic stem cell transplant (HCT) is the only established curative approach for sickle cell disease (SCD). Due to the high toxicity profile of myeloablative regimens, some adult patients with severe sickle cell anemia are not eligible for such therapy. However, a new adult nonmyeloablative protocol (National Institutes of Health, NIH protocol) described by Hsieh et al. (2014) was able to achieve a curative degree of mixed donor chimerisms with minimal transplant-related complications. The NIH protocol includes alemtuzumab, low dose total-body irradiation (TBI) of 300 cGy, and prolonged sirolimus for graft-versus-host disease (GVHD) prophylaxis for those recipients with a matched-sibling donor (MSD).The Alberta Children's Hospital has adopted this published regimen for MSD HCT in adolescents and younger children with SCD since the NIH data was presented in 2013.To our knowledge, there is no published literature describing the application of the NIH protocol in a pediatric population; the youngest subject in the referenced adult study was 16 years of age.MethodsThis retrospective cohort describes outcomes of nonmyeloablative allogeneic MSD HCT in children and adolescents with SCD who underwent HCT between 2013-2017. Fourteen patients with SCD under 18 years of age at the time of HCT received the NIH conditioning regimen. HLA-matched siblings had either normal hemoglobin or sickle cell trait and of the appropriate weight/height to donate peripheral blood stem cells (PBSCs) without blood priming of the apheresis circuit.The conditioning regimen consisted of alemtuzumab 1.0 mg/kg administered subcutaneously daily divided over five days (Days -7 to Day -3). Patients received a single TBI dose of 300 cGy on day -2, with testicular shielding for male recipients. GVHD prophylaxis consisted of a sirolimus loading dose of 3mg/m2/dose (PO) on day -1, followed by 1mg/m2/dose once daily starting on Day 0. PBSCs were typically collected on Day -3 to allow for cancellation of the HCT before TBI in the event of failed mobilization. Unmanipulated PBSCs were infused fresh on Day 0. Patients were eligible for early discharge post-transplant even prior to neutrophil engraftment. Weaning of sirolimus was initiated no earlier than 1-year post-HCT and if donor T-cell chimerisms were greater than 50%. Treatment failure was defined as clinical manifestation of SCD, failure to start weaning sirolimus by 2-years post-HSCT, or a failure to complete a sirolimus wean by 2.5 years post-HCT.ResultsFourteen patients (3 M,11 F) are included on this retrospective study. Median age at HCT was 11 years. Post-HCT follow-up ranges from 1 to 48 months (median 17). There were no failed donor stem cell mobilizations. Patients received a median of 11.4x106 CD34 cells per kilogram of body weight.All patients were discharged home prior to neutrophil engraftment with a median hospital stay of 7 days (range 5-19). All patients had donor neutrophil engraftment at a median of 21 days (mean= 22, SD= 4) and platelet engraftment at median of 14 days (mean= 12, SD= 14). Six patients never required platelet transfusion. Readmission after initial discharge was required in 9/14 patients with an average of 1 readmission/patient (range 1-4), typically for fever or CMV pre-emptive therapy. One patient developed septic shock with Acinetobacter ursingii related to poor central line care at home.All patients are currently alive. Post-HCT, there have been no cases of graft failure, sickling crises, veno-occlusive disease, idiopathic pneumonia syndrome, cerebral hemorrhage, PRES, or PTLD. Although 6/14 patients had CMV reactivation, only 3 patients required pre-emptive therapy. None had CMV/EBV disease.There were no treatment failures as defined by protocol. Currently, 8 patients are off sirolimus, 1 is currently weaning, with no secondary graft failure events. Only 2 patients over 1-year post-HCT have not initiated sirolimus weaning. There have been no cases of acute or chronic graft-versus-host disease.ConclusionsNonmyeloablative conditioning regimen is safe and effective as curative therapy for children with SCD. Outpatient management pre-engraftment was feasible in this population. In contrast to adult data, sirolimus weaning was possible in most patients by one-year post-HCT. Graft integrity was maintained after discontinuation of sirolimus in all eligible patients. [Display omitted] DisclosuresGuilcher:Patient Access Solutions: Consultancy; Canada Market Research: Consultancy; Jazz pharmaceuticals: Consultancy. Bruce:Bristol-Meyers-Squibb - consultant 2016-2017: Consultancy; ovartis consult and ad board 2015-2016: Consultancy; Apopharma 2015: Consultancy.