Optimising the screening for haemoglobinopathies in pregnancy planning.

Haemoglobinopathies are among the most common inherited disorders around the world. In the United States the diagnosis of haemoglobinopathy or a carrier state is made by universal newborn screening. However, many individuals of childbearing age do not know they are a haemoglobinopathy carrier. Screening for common haemoglobinopathies is generally offered as a part of pregnancy planning so that prospective parents can be counselled regarding the risk of having a child with a haemoglobinopathy. Multiple tests exist to screen patients for presence of haemoglobinopathy carrier or disease state; however, it is crucial to order and interpret the results correctly to appropriately counsel couples. In this case series, we describe clinical scenarios where prospective parents were surprised to unexpectedly have a child with sickle cell disease, a haemoglobinopathy that causes severe clinical complications. Through these cases we demonstrate that deficiencies in testing can occur at different levels which may lead to incorrect estimation of the risk of having a child affected by a haemoglobinopathy. Consultation with a haematologist, laboratory medicine specialist, or genetic counsellor should be considered to select the appropriate test and interpret its results.

Clinical outcomes of children and adolescents with sickle cell disease and COVID-19 infection: A year in review at a metropolitan tertiary pediatric hospital.

Background: COVID-19 was declared a global pandemic in March 2020. Early reports were primarily in adults, and sickle cell disease (SCD) was classified as a risk factor for severe COVID-19 disease. However, there are a limited number of primarily multi-center studies reporting on the clinical course of pediatric patients with SCD and COVID-19. Methods: We conducted an observational study of all patients with SCD diagnosed with COVID-19 at our institution between March 31, 2020, and February 12, 2021. Demographic and clinical characteristics of this group were collected by retrospective chart review. Results: A total of 55 patients were studied, including 38 children and 17 adolescents. Demographics, acute COVID-19 clinical presentation, respiratory support, laboratory findings, healthcare utilization, and SCD modifying therapies were comparable between the children and adolescents. Seventy-three percent (N = 40) of all patients required emergency department care or hospitalization. While 47% (N = 26) were hospitalized, only 5% (N = 3) of all patients required intensive care unit admission. Patients frequently had concurrent vaso-occlusive pain crisis (VOC) (N = 17, 43%) and acute chest syndrome (ACS) (N = 14, 35%). Those with ACS or an oxygen requirement had significantly higher white blood cell count, lower nadir hemoglobin, and higher D-dimers, supporting a pro-inflammatory and coagulopathic picture. Non-hospitalized patients were more likely to be on hydroxyurea than hospitalized patients (79 vs. 50%, p = 0.023). Conclusion: Children and adolescent patients with SCD and acute COVID-19 often present with ACS and VOC pain requiring hospital-level care. Hydroxyurea treatment appears to be protective. We observed no mortality despite variable morbidity.

Reduction in vaso-occlusive events following stem cell transplantation in patients with sickle cell disease.

Hematopoietic stem cell transplantation (HSCT) is potentially curative for patients with sickle cell disease (SCD). Patients with stable donor engraftment after allogeneic HSCT generally do not experience SCD-related complications; however, there are no published data specifically reporting the change in vaso-occlusive events (VOE) after HSCT. Data regarding the number of VOEs requiring medical attention in the 2 years before allogeneic HSCT were compared with the number of VOEs in the 2 years (0-12 months and 12-24 months) after allogeneic HSCT in patients with SCD. One-hundred sixty-three patients with SCD underwent allogeneic HSCT between 2005 and 2019. The average age at the time of HSCT was 21 years (range, 7 months - 64 years). Most patients underwent nonmyeloablative conditioning (75% [N = 123]) and had a matched sibling donor (72% [N = 118]). The mean number of VOEs was reduced from 5.6 (range, 0-52) in the 2 years before HSCT to 0.9 (range, 0-12) in the 2 years after HSCT (P < .001). Among the post-HSCT events, VOE was more frequent during the first 12 months (0.8 [range, 0-12]) than at 12 to 24 months after HSCT (0.1 [range, 0-8) (P < .001)). In patients who had graft rejection (12%, N = 20), VOEs were reduced from 6.6 (range, 0-24) before HSCT to 1.1 (range, 0-6) and 0.8 (range, 0-8) at 0 to 12 months and 12 to 24 months after HSCT, respectively (P < .001). VOEs requiring medical care were significantly reduced after allogeneic HSCT for patients with SCD. These data will inform the development of novel autologous HSCT gene therapy approaches.

Long-Term Organ Function After HCT for SCD: A Report From the Sickle Cell Transplant Advocacy and Research Alliance.

Hematopoietic cell transplantation (HCT) is an established cure for sickle cell disease (SCD) supported by long-term survival, but long-term organ function data are lacking. We sought to describe organ function and assess predictors for dysfunction in a retrospective cohort (n = 247) through the Sickle cell Transplant Advocacy and Research alliance. Patients with <1-year follow-up or graft rejection/second HCT were excluded. Organ function data were collected from last follow-up. Primary measures were organ function, comparing pre- and post-HCT. Bivariable and multivariable analyses were performed for predictors of dysfunction. Median age at HCT was 9.4 years; the majority had HbSS (88.2%) and severe clinical phenotype (65.4%). Most received matched related (76.9%) bone marrow (83.3%) with myeloablative conditioning (MAC; 57.1%). Acute and chronic graft-versus-host disease (GVHD) developed in 24.0% and 24.8%. Thirteen patients (5.3%) died ≥1 year after HCT, primarily from GVHD or infection. More post-HCT patients had low ejection or shortening fractions than pre-HCT (0.6% â†’ 6.0%, P = .007 and 0% â†’ 4.6%, P = .003). The proportion with lung disease remained stable. Eight patients (3.2%) had overt stroke; most had normal (28.3%) or stable (50.3%) brain magnetic resonance imaging. On multivariable analysis, cardiac dysfunction was associated with MAC (odds ratio [OR] = 2.71; 95% confidence interval [CI], 1.09-6.77; P = .033) and severe acute GVHD (OR = 2.41; 95% CI, 1.04-5.62; P = .041). Neurologic events were associated with central nervous system indication (OR = 2.88; 95% CI, 2.00-4.12; P < .001). Overall organ dysfunction was associated with age ≥16 years (OR = 2.26; 95% CI, 1.35-3.78; P = .002) and clinically severe disease (OR = 1.64; 95% CI, 1.02-2.63; P = .043). In conclusion, our results support consideration of HCT at younger age and use of less intense conditioning.

Low Rates of Cerebral Infarction after Hematopoietic Stem Cell Transplantation in Patients with Sickle Cell Disease at High Risk for Stroke.

Hematopoietic stem cell transplantation (HSCT) can be curative for sickle cell disease (SCD). SCD patients with cerebrovascular disease are often referred for HSCT. The objective of this study was to describe neurologic outcomes after HSCT in patients with pre-existing SCD and cerebrovascular comorbidity. Patients with SCD treated with HSCT at a single center between 1996 and 2019 were identified. Patients with cerebral ischemia and/or vasculopathy before undergoing HSCT were included. Patients with graft failure were excluded. The cohort was divided into 3 groups: symptomatic stroke, vasculopathy without symptomatic stroke, and isolated silent cerebral infarction (SCI). Magnetic resonance imaging/angiography and neurologic assessments pre- and post-HSCT were analyzed to assess outcomes. In a cohort of 44 patients, there were 25 with symptomatic infarction, 10 with vasculopathy, and 9 with isolated SCI. Post-HSCT ischemic injury (2 symptomatic strokes, 2 SCIs) was identified in 4 patients, all with previous symptomatic infarction. Within this group (n = 25), the post-HSCT incidence of subsequent symptomatic infarction was 1.6 events/100 patient-years, and SCIs occurred at a rate of 2.2 events/100 patient-years. No patient had progression of vasculopathy post-HSCT. Our data show a low incidence of new ischemic injury after successful HSCT for SCD. Patients with a history of both symptomatic stroke and vasculopathy are at greatest risk for post-HSCT ischemic injury.

Human leukocyte antigen (HLA) class I antibodies and transfusion support in paediatric HLA-matched haematopoietic cell transplant for sickle cell disease.

The relevance of donor-specific human leukocyte antigen (HLA) antibodies in HLA-mismatched haematopoietic cell transplant (HCT) is known, but the importance of HLA antibodies in HLA-matched HCT is unclear. We hypothesized that HLA antibodies detected before HCT would cause platelet transfusion refractoriness during HCT and investigated this in a multi-centre study. Pre-HCT samples from 45 paediatric patients with sickle cell disease (SCD) undergoing HLA-matched HCT were tested for HLA class I antibodies. The number of platelet transfusions received before day +45 was compared between those with and without antibodies. Thirteen of 45 (29%) patients had a positive HLA class I antibody screen, and these patients received significantly more platelet transfusions than patients without antibodies (median 19 vs. 7·5, P = 0·028). This platelet transfusion association remained significant when controlling for conditioning regimen. Among alloimmunized patients, there was no association between the panel-reactive antibody and the number of platelet transfusions. Patients with HLA class I antibodies also had a higher incidence of acute graft-versus-host disease (GVHD): 6/13 (46%) vs. 3/32 (9%), P = 0·011. Pre-HCT HLA class I alloimmunization is associated with increased platelet transfusion support and acute GVHD in paediatric HLA-matched HCT for SCD. Further studies are needed to investigate the pathobiology of this association.

Inpatient Ordering of Home Hydroxyurea by Residents for Hospitalized Patients With Sickle Cell Disease.

BACKGROUND: Hydroxyurea is a well-established disease-modifying medication for sickle cell disease (SCD). At some institutions, hydroxyurea can only be ordered by "chemotherapy-certified" providers which may not include pediatric resident physicians. METHODS: We conducted a survey of 39 American pediatric hospitals regarding their policy on resident hydroxyurea ordering for SCD. Our institution changed its policy in June 2016 to allow residents to order hydroxyurea for hospitalized patients with SCD who were already on hydroxyurea at home. We conducted a retrospective review of the medical records of a random sample of patients with SCD on hydroxyurea admitted the year before and the year after this policy change. RESULTS: In our national survey, 51% of surveyed hospitals allowed residents to order hydroxyurea, 19% required a second signature, and 30% did not allow residents to order hydroxyurea. In our institutional study, patients after the policy change were significantly more likely to have received their home hydroxyurea by hospital day 1: before 62/90 (69%) versus after 105/119 (88%), P=0.0005. The proportion of patients who inappropriately received hydroxyurea was very low in both groups: before 1/91 (1%) versus after 3/126 (2%), P=0.64, with no serious adverse clinical events due to inappropriate hydroxyurea administration. CONCLUSIONS: Considerable national variation in practice currently exists in regards to resident hydroxyurea ordering hospital policies. A policy allowing residents to order hydroxyurea significantly increased the likelihood of a patient receiving hydroxyurea while hospitalized with no significant increase in inappropriate hydroxyurea administration. Resident hydroxyurea ordering seems safe and beneficial.

Characterization of natural killer cells expressing markers associated with maturity and cytotoxicity in children and young adults with sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) is increasingly recognized as a red blood cell disorder modulated by abnormally increased inflammation. We have previously shown that in patients with SCD not on a disease-modifying therapy (hydroxyurea or chronic transfusions), natural killer (NK) cell numbers are increased. In the current study, we further investigated the NK cell function to determine if there was evidence of increased activation and cytotoxicity. PROCEDURE: We conducted a cross-sectional study of 44 patients with HbSS/HbSß0 thalassemia at steady state (hydroxyurea = 13, chronic transfusion = 11, no disease-modifying therapy = 20) and 23 healthy controls. Using a fresh blood sample, NK immunophenotyping was performed as follows: NK cells (CD3- CD56+ lymphocytes) were evaluated for makers associated with activation (NKG2D, NKp30, NKp44, and CD69) and maturity (CD57, killer immunoglobulin-like receptors (KIR), and CD56dim). Degranulation and cytotoxicity assays were performed to evaluate NK cell function. RESULTS: Patients with SCD who were not on disease-modifying therapy had a higher number of NK cells with an immunophenotype associated with increased cytotoxicity (NKG2D+ , NKp30+ , CD56dim+ , and KIR+ NK cells) compared with healthy controls and patients on hydroxyurea. NK cells from SCD patients not on disease-modifying therapy demonstrated significantly increased cytotoxicity (measured by assaying NK cell killing of the K562 cell line) compared with healthy controls (P = 0.005). Notably, NK cell cytotoxicity against K562 cells in the hydroxyurea or chronic transfusion patients was not significantly different from that in healthy controls. CONCLUSION: SCD is associated with increased NK cell function as well as increased NK cell numbers, which appears to be normalized with disease-modifying therapy.

Views of parents of children with sickle cell disease on pre-implantation genetic diagnosis.

Pre-implantation genetic diagnosis (PGD) is an option for parents who have a child with sickle cell disease (SCD) to have another child without SCD. We conducted a survey of 19 parents with at least one child with SCD to investigate views on PGD. Before education, 44% of parents were aware of PGD. All parents rated PGD education as important. All parents considering another child also reported interest in using PGD if insurance covered its costs. Parents who have a child with SCD appear to be interested in PGD and educational tools informing this group about PGD should be developed.

Immunophenotypic parameters and RBC alloimmunization in children with sickle cell disease on chronic transfusion.

Alloimmunization against red blood cell (RBC) antigens is a cause of morbidity and mortality in transfused patients with sickle cell disease (SCD). To investigate distinguishing characteristics of patients who develop RBC alloantibodies after transfusion (responders) versus those who do not (non-responders), a cross-sectional study of 90 children with SCD on chronic RBC transfusion therapy at a single institution was conducted in which 18 immune parameters (including T and B cell subsets) were tested via flow cytometry, and medical records were reviewed. RBC alloimmunization was present in 26/90 (29%) patients, with anti-E, K, and C among the most commonly detected alloantibodies despite prophylactic matching for these antigens at the study institution. In addition, RBC autoantibodies had been detected in 18/26 (69%) of alloimmunized versus 7/64 (11%) of non-alloimmunized patients (P < 0.0001). Alloimmunized patients were significantly older (median 13.0 years vs. 10.7 years, P = 0.010) and had more RBC unit exposures (median 148 U vs. 82 U, P = 0.020) than non-alloimmunized patients. Sex, age at initiation of chronic transfusion, splenectomy, stroke, and transfusion outside of the study institution were not significantly associated with RBC alloimmunization. Alloimmunized patients had a significantly increased percentage of CD4+ T memory cells compared to non-alloimmunized patients (57% vs. 49%, P = 0.0047), with no other significant differences in immune cell subsets or laboratory values detected between these groups. Additional research of RBC alloimmunization is needed to optimize transfusion therapy and to develop strategies to prevent alloimmunization.