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Objective: To test the hypothesis that caregivers' or adult participants' low ratings of provider communication are associated with more hospital admissions among adults and children with sickle cell disease (SCD), respectively. Secondarily, we determined whether there was an association between the caregivers' or participants' health literacy and rating of providers' communication. Methods: Primary data were collected from participants through surveys between 2014 and 2016, across six sickle cell centers throughout the U.S. In this cross-sectional cohort study, 211 adults with SCD and 331 caregivers of children with SCD completed surveys evaluating provider communication using the Consumer Assessment of Healthcare Providers and Systems (CAHPS), healthcare utilization, health literacy, and other sociodemographic and behavioral variables. Analyses included descriptive statistics, bivariate analyses, and logistic regression. Results: Participants with better ratings of provider communication were less likely to be hospitalized (odds ratio (OR) = 0.54, 95% confidence interval (CI) = [0.35, 0.83]). Positive ratings of provider communication were associated with fewer readmissions for children (OR = 0.23, 95% CI = [0.09, 0.57]). Participants with better ratings of provider communication were less likely to rate their health literacy as lower (regression coefficient (B) = -0.28, 95% CI = [-0.46, -0.10]). Conclusions: Low ratings of provider communication were associated with more hospitalizations and readmissions in SCD, suggesting the need for interventions targeted at improving patient-provider communication which could decrease hospitalizations for this population.

Outpatient care is critical in the management of chronic diseases, including sickle cell disease (SCD). Risk factors for poor adherence with clinic appointments in SCD are poorly defined. This exploratory study evaluated associations between modifying variables from the Health Belief Model and missed appointments.We surveyed adults with SCD (n = 211) and caregivers of children with SCD (n = 331) between October 2014 and March 2016 in six centres across the U.S. The survey tool utilized the framework of the Health Belief Model, and included: social determinants, psychosocial variables, social support, health literacy and spirituality.A majority of adults (87%) and caregivers of children (65%) reported they missed a clinic appointment. Children (as reported by caregivers) were less likely to miss appointments than adults (OR:0.22; 95% CI:(0.13,0.39)). In adults, financial insecurity (OR:4.49; 95% CI:(1.20, 20.7)), health literacy (OR:4.64; 95% CI:(1.33, 16.15)), and age (OR:0.95; 95% CI:(0.91,0.99)) were significantly associated with missed appointments. In all participants, lower spirituality was associated with missed appointments (OR:1.83; 95%CI:(1.13, 2.94)). The most common reason for missing an appointment was forgetfulness (adults: 31%, children: 26%). A majority thought reminders would help (adults: 83%, children: 71%) using phone calls (adults: 62%, children: 61%) or text messages (adults: 56%, children: 51%).Our findings demonstrate that modifying components of the Health Belief Model, including age, financial security, health literacy, spirituality, and lacking cues to action like reminders, are important in missed appointments and addressing these factors could improve appointment-keeping for adults and children with SCD.

Objective: Hospital admissions are significant events in the care of individuals with sickle cell disease (SCD) due to associated costs and potential for quality of life compromise. Methods: This cross-sectional cohort study evaluated risk factors for admissions and readmissions between October 2014 and March 2016 in adults with SCD (n = 201) and caregivers of children with SCD (n = 330) at six centres across the U.S. Survey items assessed social determinants of health (e.g. educational attainment, difficulty paying bills), depressive symptoms, social support, health literacy, spirituality, missed clinic appointments, and outcomes hospital admissions and 30-day readmissions in the previous year. Results: A majority of adults (64%) and almost half of children (reported by caregivers: 43%) were admitted, and fewer readmitted (adults: 28%; children: 9%). The most common reason for hospitalization was uncontrolled pain (admission: adults: 84%, children: 69%; readmissions: adults: 83%, children: 69%). Children were less likely to have admissions/readmissions than adults (Admissions: OR: 0.35, 95% CI: [0.23,0.52]); Readmissions: 0.23 [0.13,0.41]). For all participants, missing appointments were associated with admissions (1.66 [1.07, 2.58]) and readmissions (2.68 [1.28, 6.29]), as were depressive symptoms (admissions: 1.36 [1.16,1.59]; readmissions: 1.24 [1.04, 1.49]). In adults, difficulty paying bills was associated with more admissions, (3.11 [1.47,6.62]) readmissions (3.7 [1.76,7.79]), and higher spirituality was associated with fewer readmissions (0.39 [0.18,0.81]). Discussion: Missing appointments was significantly associated with admissions and readmissions. Findings confirm that age, mental health, financial insecurity, spirituality, and clinic attendance are all modifiable factors that are associated with admissions and readmissions; addressing them could reduce hospitalizations.

Sickle cell disease (SCD) results in neuropsychological complications that place adolescents at higher risk for limited educational achievement. A first step to developing effective educational interventions is to understand the impact of SCD on school performance. The current study assessed perceptions of school performance, SCD interference and acceptability of educational support strategies in adolescents with SCD. To identify potential risk factors, the relationships between school performance, SCD interference and demographics were also examined. Thirty adolescents aged 12 to 20 years completed demographics and SCD school performance questionnaires. Approximately 37% of participants reported receiving special education services, but more than 60% reported that SCD interfered with their school performance. Females reported that SCD impacted their schooling more than males (X2 (1, n = 30) = 5.00, p < .05). Study findings provide important insights into demographic risk factors and support the need for individualized health and educational plans for adolescents with SCD.

Practice guidelines have been developed for pediatric patients with hematologic disorders, and similar to guidelines for other diseases, adherence is variable. Quality improvement initiatives can move implementation of the guidelines from variable to frequent. For children with sickle cell disease (SCD), quality improvement interventions have significantly improved outcomes related to the effective and timely management of acute vaso-occlusive crises (VOC), reducing the frequency of VOC necessitating hospitalization by administration of hydroxyurea, prevention of stroke, and reducing infections such as influenza. Although there are guidelines for the care and treatment of children with hemophilia, quality improvement initiatives are in the early stages.

Background : Approximately 100,000 persons with sickle cell disease (SCD) live in the United States, including 15,000 in the Midwest. Unfortunately, many patients experience poor health outcomes due to limited access to primary care providers (PCPs) who are prepared to deliver evidence-based SCD care. Sickle Treatment and Outcomes Research in the Midwest (STORM) is a regional network established to improve care and outcomes for individuals with SCD living in Indiana, Illinois, Michigan, Minnesota, Ohio, and Wisconsin. Methods : STORM investigators hypothesized that Project ECHO ® methodology could be replicated to create a low-cost, high-impact intervention to train PCPs in evidence-based care for pediatric and young adult patients with SCD in the Midwest, called STORM TeleECHO. This approach utilizes video technology for monthly telementoring clinics consisting of didactic and case-based presentations focused on the National Heart, Lung and Blood Institute (NHLBI) evidence-based guidelines for SCD. Results : Network leads in each of the STORM states assisted with developing the curriculum and are recruiting providers for monthly clinics. To assess STORM TeleECHO feasibility and acceptability, monthly attendance and satisfaction data are collected. Changes in self-reported knowledge, comfort, and practice patterns will be compared with pre-participation, and 6 and 12 months after participation. Conclusions : STORM TeleECHO has the potential to increase implementation of the NHLBI evidence-based guidelines, especially increased use of hydroxyurea, resulting in improvements in the quality of care and outcomes for children and young adults with SCD. This model could be replicated in other pediatric chronic illness conditions to improve PCP knowledge and confidence in delivering evidence-based care. Keywords: provider education; telementoring; continuing education; sickle cell disease (Published: 24 November 2016) Citation: Med Educ Online 2016, 21: 33616 - http://dx.doi.org/10.3402/meo.v21.33616

Background: Genetic transfer of an anti-sickling β87-globin lentiviral vector (LV) into hematopoietic stem cells (HSC) followed by myeloablative transplant has cured one child with sickle cell anemia (SCA) (NEJM 2017), although it was not successful in 7 subsequent adult SCA patients, and modifications to intensify ablative conditioning, improve HSC dose, gene transfer are underway (Blood 130 Suppl 1: 527, 2017). Based upon our preclinical data (Blood 2009), we embarked upon a Reduced Intensity Conditioning (RIC) Phase I/II Pilot Study on Gene Transfer in Patients with SCA with a modified γ-Globin LV (NCT02186418), hypothesizing this approach will be safe, feasible and efficacious; Moreover, RIC will have significantly less toxicity, costs, and be implementable in many transplant centers, including those in some of the resource-poor countries, where supportive therapies for myeloablative transplants are unavailable, and where majority of SCA patients exist. Methods: Adult patients with severe SCA deemed eligible were transfused/erythrocytapheresed prior to HSC collection and transfused for 6 months post-transplant (PT) to Hb>10g/dl and HbS~30%. CD34+ HSC were collected via bone marrow harvest (BMH) and/or plerixafor mobilized Peripheral Blood Stem Collection (PBSC), selected for CD34+ cells and transduced. Patients received a single dose of IV melphalan (140mg/m2 BSA) 36hr prior to infusion of γ-globin modified (GM)-HSC. Patients were monitored for adverse events (AE), engraftment, vector copy number (VCN), modified HbF (HbF*) expression and clinical features of SCA. Results: Two SCA patients (35yo and 25yo) with HbS-β0 thalassemia genotype were treated. CD34+ HSC were collected via multiple BMH (P1) and BMH+PBSC (P2). Follow up data are available for 6 and 12mo on P1 and P2. P1 received 1x106 CD34+ cells/kgbw [vector copy number (VCN) 0.22], and P2 received 6.9x106 CD34+ cells/kgbw [VCN 0.46]. Time to neutrophil engraftment (ANC ≥ 500) was day 9 and 7 post-transplant (PT) in P1 and P2, respectively, and time to Plt recovery (Plt>50K) was day 14 PT in both. Patients included in this trial had severe disease and continued to have pre-existing chronic pain requiring significant opiates; hence ~80% of the AEs were pain events; other AEs were anticipated transient laboratory AEs associated with melphalan. Following GM-HSC infusion, both patients showed a progressive rise in HbF* (a point mutation in the γ-globin LV allows distinction from endogenous HbF by HPLC) starting from day 30 PT. Since patients had transfused HbA containing RBCs in the initial 6 months, HbF*/(HbF*+HbS) was calculated, and was 20% and 21% in P1 and P2 at day 180 PT and VCN 0.2-0.4, detected in all lineages. Integration site analysis, performed on the infused products (Day 0), at day 30 PT on P1 and P2, and on day 180 PT on P1 demonstrated highly polyclonal pattern of integration. At 1 yr PT, P1 had 20% HbF* (2.1g/dl HbF*, total Hb 10.6) with a stable VCN of 0.2-0.4 in multiple lineages in bone marrow and peripheral blood. The baseline Hb of P1 was 7.5-8.5g/dL prior to transplant. In the preceding 2 years prior to transplant, both patients were admitted for pain crises/acute chest >5-6 times/yr, and had chronic pain requiring chronic opiates. Chronic pain persisted for 4-5 months PT in P1, after which P1 has not required IV opiates, negligible oral opiates and has had no hospital visits/admissions with acute sickle events. P2 has required decreasing amounts of oral opiates for chronic back pain. Conclusions: Early results from 2 SCA adults treated with a modified γ-globin LV modified autologous HSC following RIC transplant showed excellent safety, feasibility, with minimal post-transplant toxicity, rapid count recovery, and sustained stable genetically modified cells in peripheral blood and bone marrow. The first patient shows significant clinical amelioration of the SCA phenotype at 1 year PT, with 20% vector-derived HbF (HbF*) that has caused amelioration of anemia, near elimination of chronic pain and absence of acute sickle events. The second patient, although still early post-transplant shows a similar HbF* trajectory. Additional study data will demonstrate whether this level of HbF* will provide consistent clinical benefit to patients with severe SCA. These early results, especially following a RIC transpant, are extremely promising; and if sustained, will provide a 'transportable' safe and feasible gene therapy for SCA. Disclosures Malik: CSL Behring: Patents & Royalties. Quinn:Global Blood Therapeutics: Research Funding; Silver Lake Research Corporation: Research Funding; Amgen: Research Funding.

Background: Hydroxyurea is now the standard of care for children with sickle cell anemia (SCA). Results from the BABY HUG study and recommendations from the 2014 NHLBI Guidelines have led to early initiation (increasingly before 1 year of age) of hydroxyurea for many patients. Given the known variability in hydroxyurea pharmacokinetics (PK), treatment response (HbF%), and maximum tolerated dose (MTD), we hypothesized that individualized dosing would provide the optimal treatment approach. Methods: The Therapeutic Response Evaluation and Adherence Trial (TREAT, ClinicalTrials.gov NCT02286154) is a prospective study of a personalized, PK-guided dosing model of hydroxyurea for children with SCA. Using population PK model-based Bayesian estimation, each participant's PK data are used to generate an individualized starting hydroxyurea dose that targets an area under the curve associated with actual MTD. Clinical follow-up and subsequent dose adjustments target MTD, usually defined by ANC Results:The analysis of children starting hydroxyurea before 2 years of age included 33 participants (of 47 total TREAT enrollments), who contributed a total of 59.5 patient-years of hydroxyurea therapy. The mean age (±SD) at hydroxyurea initiation was 1.0±0.4 years of age. The average PK-guided, individualized starting dose was 27.8±5.3 mg/kg/day, higher than conventional and BABY HUG initial dosing (20 mg/kg/day). For children who have completed 12 months of therapy (n=24), effects in hematologic laboratory data are remarkable with average 35.9±8.9% HbF and hemoglobin concentration of 10.2±1.1 g/dL after 12 months of therapy (compared to 29.3±8.8% and 9.2±1.3 g/dL at baseline). The majority (70%) of these participants have HbF>30% and almost half achieved HbF>40% after 12 months of hydroxyurea. This hematological response is more robust than what was observed in BABY HUG (HbF=22.4%, Hb=9.1 g/dL after two years of therapy, Wang WC et al. Lancet 2011). In the TREAT cohort, there were no episodes of dactylitis, acute splenic sequestration, or stroke. There were 111 emergency room or sick outpatient clinic visits for this young cohort; 107 ED/clinic visits (without subsequent hospitalization) were for fever, URI symptoms, GI illness, or other non-specific complaints unrelated to SCA, while only 4 (3.6%) visits were for pain. There were 38 hospitalizations in 17 participants, mostly for routine evaluation of fever (66%), but no positive blood cultures and no admissions for febrile neutropenia. The average length of hospitalization was 2.8±2.4 days with 81% of participants discharged within 72 hours of admission. There were 3 episodes of acute chest syndrome in 2 patients, two of whom required PRBC transfusion. Including all types of visits, there were only 6 pain events, equivalent to 10.1 pain events per 100 patient-years, which is much lower than the published 94 events per 100 patient-years in the hydroxyurea treatment arm of BABY HUG (Thornburg CD et al. Blood 2012). There were 37 TCD exams performed in 16 participants, all normal except for one patient with conditional velocities that normalized with hydroxyurea. There were no significant differences from baseline to month 12 in either RBC pit counts or cystatin C values. Conclusions: Hydroxyurea initiation at an early age using PK-guided dosing provides significant clinical benefits for young children with sickle cell anemia. These TREAT study data suggest that initiating hydroxyurea around one year of life using a personalized dosing strategy can provide better clinical and laboratory benefits than starting at the conventional 20 mg/kg/day weight-based dose. Very high HbF levels are observed at modest and well-tolerated doses of hydroxyurea, perhaps because treatment was initiated before the process of HbF inactivation is complete. Continued long-term follow-up of these patients will determine whether these will be sustained and able to prevent both short- and long-term complications of SCA. Disclosures Malik: CSL Behring: Patents & Royalties. Quinn:Silver Lake Research Corporation: Research Funding; Global Blood Therapeutics: Research Funding; Amgen: Research Funding. Ware:Biomedomics: Research Funding; Nova Laboratories: Consultancy; Bristol Myers Squibb: Research Funding; Addmedica: Research Funding; Global Blood Therapeutics: Other: advisory board; Agios: Other: advisory board; Novartis: Membership on an entity's Board of Directors or advisory committees.

Keywords: sickle cell disease; atypical haemolytic uraemic syndrome; eculizumab; thrombotic microangiopathy; complement mutations

Background: Although increase prevalence of airway hyper-reactivity (AHR) has been detected in children, and even adults with sickle cell disease (SCD) using methacholine provocative challenge test (MCT), AHR was not been found to be associated with clinical asthma.Hence, the clinical implications of AHR in SCD are unknown. Furthermore, AHR studies in SCD patients using MCT lack comparisons with a control population. We recently showed that increased placenta growth factor (PlGF) levels in sickle mice causes AHR by upregulating leukotriene synthesis and inflammation. We therefore designed a prospective study to determine the prevalence of AHR in children and young adults with SCD, and in unaffected siblings living in the same household as a control population, and also determine the biochemical and clinical implications of AHR in SCD. Methods: A total of 67 patients with SCD and 14 unaffected siblings of the patients enrolled on to the study for determining baseline AHR (ClinicalTrials.gov Identifier: NCT00448370). Chief eligibility criteria included a diagnosis of SCD (HbSS, HbSC or HbS b-thalassemia) confirmed by hemoglobin electrophoresis or gene sequencing, ages 5.5 years to 30 years who were able to complete pulmonary function testing and were at baseline/steady state (no acute sickle events 3 weeks prior or acute chest syndrome (ACS) 4 weeks prior). Excluded were patients taking anti-leukotriene medications within 30 days prior, although patients with SCD who had a known history of asthma but not on leukotriene inhibitors were eligible. Patients with chronic transfusions, congenital lung or heart condition, or other medical condition that could affect the pulmonary function testing were also ineligible. Unaffected siblings of the 67 enrolled SCD patients living in the same household were offered enrollment for MCT and those consenting were enrolled. Results: 64 SCD patients and 14 siblings underwent a MCT; 3 of 67 SCD patients had FEV116mg/mL; borderline AHR=PC20 4-16mg/mL; mild AHR=PC20 1-3mg/mL and moderate-severe AHR=PC20 Conclusions: There was a higher prevalence of mild to severe AHR (51%) in patients with SCD, compared to a 14% prevalence of mild AHR in siblings living in the same household. The higher degree of AHR was associated with increased SCD morbidity - increased rates of admission from ACS and pain crisis, when compared to those with no AHR. AHR was associated with higher leukotrienes and a trend towards higher PlGF target gene induction. Together, our data suggests that AHR may be a biomarker for SCD morbidity, and may also be a therapeutic target, since blockade of PlGF or leukotriene synthesis in patients with severe AHR may reduce SCD morbidity. Disclosures No relevant conflicts of interest to declare.

Sickle Treatment and Outcomes Research in the Midwest (STORM) is a regional sickle cell network, funded by the Health Resources and Services Administration Treatment Demonstration Project (HRSA U1EMC27863), established to improve outcomes for individuals with sickle cell disease (SCD) living in Indiana, Illinois, Michigan, Minnesota, Ohio and Wisconsin. The STORM network is led by pediatric and adult hematologists who coordinate network activities in each state, along with a Regional Coordinating Center that organizes efforts throughout the Midwest. The goal of the STORM network is to increase the number of pediatric and adult primary care providers (PCP) who are knowledgeable about the management and treatment of SCD, and who are willing to prescribe and manage hydroxyurea therapy as a means to improve medical care for the approximately 15,000 individuals living with SCD in the Midwest. One PCP engagement strategy that has been implemented to increase provider knowledge in the region is replication of the Project ECHOTM (Extension for Community Healthcare Outcomes) telementoring model. Project ECHO was developed by the University of New Mexico to utilize low-cost, high-impact video technology to link expert inter-disciplinary specialist teams with primary care providers to improve management of chronic diseases. This guided practice telementoring model delivers complex specialty medical care to underserved areas, reduces health disparities, and increases workforce capacity. Project ECHO's methodology is based on 1) using telehealth technology to build healthcare resources where they are scarce; 2) sharing best practices to reduce variation in clinical care; 3) utilizing practice-based learning to develop specialty expertise among providers; and 4) monitoring and evaluating provider outcomes. Project ECHO has demonstrated improved healthcare outcomes in Hepatitis C and several other chronic diseases, and is now being piloted by STORM to test its feasibility and applicability for SCD by using a regional approach with CME accreditation. STORM network site physician leads in each state are recruiting multi-disciplinary primary care teams to participate as "spokes" in monthly SCD TeleECHO clinics. The "hub" led by the STORM Regional Coordinating Center, located at Cincinnati Children's Hospital Medical Center, coordinates implementation and evaluation of the telementoring clinics, delivered through monthly teaching sessions. STORM TeleECHO participants log onto an internet-based virtual meeting site, using a webcam to interact during the session. STORM TeleECHO clinics include brief didactic presentations from nationally-recognized SCD content experts with topics and curriculum based on the National Heart Lung and Blood Institute Evidence-Based Management of Sickle Cell Disease guidelines released in 2014. TeleECHO teaching clinics also include 1-2 de-identified, HIPAA protected case discussions (pediatric and adult) presented by providers who would like medical and psychosocial feedback on management of challenging clinical scenarios. Providers participating in the STORM TeleECHO complete an initial survey assessing knowledge and comfort levels, practice behaviors (including hydroxyurea prescribing practices) and clinic demographics. Satisfaction surveys are sent to participants after each session as part of the CME-credit evaluation. Follow-up surveys at 6 months and 1 year will assess satisfaction, knowledge, comfort level and changes in practice. STORM's TeleECHO was launched in March 2016. Preliminary data indicate an interest in STORM TeleECHO teaching sessions by both pediatric and adult providers across the Midwest region. Future efforts will expand the network to more PCPs in the region, while improving the applicability and utility of STORM TeleECHO in SCD through provider assessment. Disclosures Ware: Global Blood Therapeutics: Consultancy; Biomedomics: Research Funding; Bristol Myers Squibb: Research Funding; Addmedica: Research Funding; Nova Laboratories: Consultancy; Bayer Pharmaceuticals: Consultancy.

Background: Hydroxyurea is the primary disease modifying therapy for patients with sickle cell anemia (SCA). The clinical and laboratory benefits of hydroxyurea are the greatest when escalated to the maximum tolerated dose (MTD). The process of dose escalation to MTD requires expertise and can be tedious, often taking 6-12 months to titrate to the optimal dose. In addition, due in part to inter-patient variability in hydroxyurea pharmacokinetics (PK), the MTD varies among patients with a range of 15-35 mg/kg/day. We utilized a population PK model in combination with Bayesian estimation and a sparse sampling strategy, to individualize dosing of children starting hydroxyurea treatment. Methods: The Therapeutic Response Evaluation and Adherence Trial (TREAT, ClinicalTrials.gov NCT02286154) is a prospective study of hydroxyurea for children with SCA. The primary objective is to develop and evaluate a population PK-based model to predict hydroxyurea MTD through an individualized dosing strategy. A sparse sampling approach was developed to allow practical sampling from young children with SCA. The sampling strategy includes administering a single oral 20 mg/kg dose followed by collection of small quantities of blood (~100uL) at three post-dosing time points (15-20 minutes, 50-60 minutes, and ~3 hours). Baseline labs (including liver and renal function) are typically collected by venipuncture, while the other two samples are drawn by fingerstick or heelstick. Plasma hydroxyurea concentrations are measured using HPLC using an internal standard of methylurea. Using the population PK model with Bayesian estimation and hydroxyurea concentrations measured at the three specified time points, hydroxyurea exposure is estimated using specialized therapeutic drug monitoring software (MWPharm, Mediware, Prague, Czech Republic). Using the area under the curve (AUC0-inf) estimated by the model, we calculate a starting dose that is predicted to achieve an AUC of 115 ug*h/mL, which was the mean AUC value at MTD for a large cohort of children from a previous study (Dong M et al. Br J Clin Pharmacol 2016). The primary objective is to select a starting dose that is close to actual MTD, to reduce the time to maximum therapeutic effect and need for dose modifications before achieving MTD. Results: From December 2014 through June 2016, 20 children taking taking hydroxyurea for the first time were enrolled in TREAT. Seventeen of the 20 participants had all 3 post-treatment PK samples collected and processed to allow calculation of an individualized PK-based dose, while 3 had difficulties in sampling or processing that prevented a safe PK-guided dose recommendation. These 3 participants were started at the standard hydroxyurea dose of 20 mg/kg/day. The Table summarizes baseline characteristics for the initial study population, notable for a very young starting age with 13/20 (65%) less than two years of age. Twelve children with PK-based initial dosing have been treated with hydroxyurea for at least six months. Despite the young starting age, after six months of hydroxyurea, children have documented increases in total Hb (1.4+/-1.9 g/dL), HbF (11.3+/-6.4%), and MCV (15+/-8 fL) and decreases in absolute reticulocyte count (-217+/-128 x 109/L) and absolute neutrophil count (-1.0+/-1.9 x 109/L). In 9 of 12 participants, the PK-guided initial dose remained the best clinical dose at six months without significant dose changes except for minor adjustments for weight. Two patients required a single dose escalation due to inadequate marrow suppression, while one required a dose hold and decrease due to neutropenia during and following a viral infection. Conclusions: These data demonstrate that a sparse sampling approach, requiring only 3 blood samples over 3 hours, is able to accurately estimate hydroxyurea exposure in children with SCA. Hydroxyurea exposure, as defined by AUC, was similar with this sparse sampling approach as previous studies that relied upon a more standard and prolonged PK sampling approach. This population PK model is then able to predict a safe starting dose of hydroxyurea that approximates the actual MTD, with clinically significant improvements in laboratory parameters following six months of therapy. This individualized PK-guided dosing regimen should simplify hydroxyurea dosing and reduce the time interval to reach MTD and maximal clinical benefits. Table Table. Disclosures Kalfa: Baxter/Baxalta/Shire: Research Funding. Quinn:Silver Lake Research Corporation: Consultancy; Amgen: Research Funding; Eli Lilly: Research Funding. Ware:Nova Laboratories: Consultancy; Addmedica: Research Funding; Global Blood Therapeutics: Consultancy; Bayer Pharmaceuticals: Consultancy; Biomedomics: Research Funding; Bristol Myers Squibb: Research Funding.

Hereditary spherocytosis (HS) is a genetically and phenotypically heterogeneous hemolytic anemia caused by deficiency in red blood cell (RBC) cytoskeleton proteins leading to disruptions in the vertical association of the cytoskeleton with the RBC lipid bilayer. Monoallelic mutations in the genes encoding ankyrin (ANK1), beta-spectrin (SPTB) and band 3 (SLC4A1) or biallelic mutations in the genes encoding alpha-spectrin (SPTA1), ankyrin, and protein 4.2 (EPB42) result in HS. Autosomal recessive HS due to compound heterozygous defects in SPTA1 is typically severe and diagnosis based on phenotypic assays like RBC morphology, osmotic fragility or ektacytometry is complicated by transfusion dependence resulting in most of the circulating RBCs to be of donor origin. We have developed a rapid comprehensive next-generation sequencing-based assay that evaluates 27 genes with published disease-causing mutations for RBC cytoskeletal disorders, enzymopathies, and CDAs. We describe here patients with hemolytic anemia due to SPTA1 mutations, identified utilizing this assay, and their phenotype-genotype correlation. Each of these cases, when possible, has been also evaluated with ektacytometry and immunoblotting of RBC ghosts for alpha-spectrin quantitation. Wichterle et al in 1996 had estimated that alphaLEPRA(Low Expression PRAgue) mutation (c.4339-99C>T) occurs in SPTA1 gene in about 5% of Caucasians. This mutation leads to activation of an alternate acceptor splice site at position -70 of intron 30, causing frame shift and premature termination, thereby leading to decrease in alpha-spectrin production in this allele to about 16% of normal. We have found a cohort of three transfusion-dependent hereditary hemolytic anemia cases where a nonsense mutation in SPTA1 gene has occurred in trans to alphaLEPRA mutation, resulting in premature termination (see Table 1). Transfusion dependence was alleviated in two of these patients after splenectomy; the third one did not have splenectomy yet. RBC phenotype explored after splenectomy revealed an ektacytometry curve indicating spherocytosis (Figure 1A) and severely decreased alpha-spectrin on immunoblotting along with significant decrease of the associated beta-spectrin (Figure 1B). A patient with moderately severe form of HS, maintaining a hemoglobin value greater than 7 g/dL and requiring only occasional transfusions during periods of illness or stress, was found to have alphaLEPRA occurring in trans to an intronic splicing mutation c.1351-1G>TG where there is substitution at nucleotide-1 of intron positioned between nucleotides 1350 and 1351 of the SPTA1 mRNA. This splicing mutation may allow for some expression of functional alpha-spectrin protein from this allele in contrast to no protein expression in the previous cases of premature termination. Alternatively, other gene mutations, not identified by the next-generation sequencing panel we used, may contribute to this patient's milder phenotype. A couple with history of two fetal losses associated with hydrops fetalis seeked genetic counseling and gave consent to have diagnostic evaluation of genes associated with non-immune hemolytic anemia using targeted next-generation sequencing. Results of the panel revealed a heterozygous frameshift SPTA1 mutation in each of the parents (c.4206delG in the father and c.4180delT in the mother). These mutations in compound heterozygous state in the offspring likely caused total absence of alpha spectrin and fatal hemolytic anemia by the time of birth. Hereditary Spherocytosis is characterized by wide phenotypic variability that will be better understood with studies of genotype-phenotype association. While complete absence of alpha-spectrin expression due to null mutations of both SPTA1 alleles is incompatible with life, a nonsense or splicing SPTA1 mutation in trans to an alphaLEPRA low expression allele causes severe or moderately severe recessive HS, respectively. Targeted next-generation sequencing can be an effective diagnostic tool particularly for patients requiring frequent transfusions that preclude meaningful phenotypical testing of their red blood cells. Figure 1. SPTA1 null mutations occurring in trans to alpha-LEPRA causing severe HS Figure 1. SPTA1 null mutations occurring in trans to alpha-LEPRA causing severe HS Figure 2. Figure 2. Disclosures Begtrup: GeneDx: Employment.