Current issues with blood transfusions in sickle cell disease

Physician perspectives about the diagnosis and management of acute chest syndrome

BACKGROUND

Acute chest syndrome (ACS) is the leading cause of mortality, accounting for 25% of all deaths among individuals with sickle cell disease (SCD). There is a lack of evidence-based laboratory and clinical risk stratification guidelines for the diagnosis and management of ACS.

STUDY DESIGN AND METHODS

To better understand physician practices for the management of ACS in the United States, we created an ACS Working Group including hematology and transfusion medicine physicians from four different SCD treatment centers in the United States. The working group created a physician survey that included physician demographics and ACS diagnostic criteria that they had to rate. The survey also included three case scenarios to assess physician attitudes about the management of ACS. Management options included supportive and preventive strategies in addition to transfusion therapy options.

RESULTS

Out of 455 physicians who received the survey, 195 responded (response rate = 43%). The respondents were primarily hematology/oncology physicians. The responses showed wide variability among physicians in how diagnostic criteria for ACS are used and how physicians risk-stratify ACS patients in their practice. The responses also reflected variability in the use of transfusions for ACS.

DISCUSSION

Based on our results, we conclude that ACS is diagnosed and managed inconsistently among expert physicians, especially in their transfusion practices due to a lack of consensus on risk stratification criteria. Our data suggest an urgent need for well-designed prospective studies to provide evidence-based guidelines and minimize management variability among physicians who care for individuals with SCD and ACS.

DFT and TD-DFT studies to elucidate the configurational isomers of ferric aerobactin, ferric petrobactin, and their ferric photoproducts

Iron-chelating siderophores such as aerobactin and petrobactin are produced by marine bacteria to sequester iron under low iron stress. Those that contain a citrate moiety undergo light-catalyzed ligand-to-metal charge transfer, inducing decarboxylation and formation of photoproducts. In this work, we employed density functional theory to obtain the optimized geometries and determine the relative energies and geometric parameters of different configurations of Fe(III)-coordinated aerobactin, petrobactin, and their photoproducts. Time-dependent density functional theory was then used to compute the UV-Vis absorption spectra of these species, and the comparison against experimental spectra further elucidated the structural configurations most likely to be adopted by these compounds. Frequency calculations provided Fe-O force constants on the same order as other siderophores. The relative energies and predicted spectra support the cis-cis C-fac configuration for ferric aerobactin and the cis-trans C-mer configuration for its photoproduct, while only mild support is found for specific configurations of the ferric petrobactin structures (meta-mer and meta-fac for the precursor, cis-cis para-fac for the photoproduct). The predicted ferric petrobactin spectra are found to be fairly insensitive to the configuration of the ferric complex.

CRISPR/Cas9 in the treatment of sickle cell disease (SCD) and its comparison with traditional treatment approaches: a review

Sickle cell disease (SCD) is a common hereditary blood disorder that profoundly impacts individuals' health, causing chronic pain, anemia, organ damage, increased susceptibility to infections, and social and psychological effects. Over the years, advances in treatment have improved the long-term outcomes of SCD patients. However, problems such as limited access to hematopoietic stem cell transplantation (HSCT) and potential complications associated with the available therapies underscore the importance of continued research and development. The recent FDA approval of Casgevy (Exagamglogene autotemcel), a genetic therapy based on CRISPR/Cas9 technology, demonstrates a comprehensive effort to address the complexity of SCD using new technologies. This review explores the potential of CRISPR/Cas9 for treating SCD and evaluates its efficacy, safety, and long-term outcomes compared to traditional treatment approaches. Long-term research is needed to comprehensively assess the safety, effectiveness, and inclusion of CRISPR/Cas9, ensuring its overall efficacy.

Impact of scheduled partial exchange transfusions on outcomes in pregnant patients with severe sickle cell disease: a retrospective study

INTRODUCTION

The incidence of feto-maternal complications is high in women with sickle cell disease. The paucity of high-quality evidence has led to conditional recommendations for transfusional support in pregnant patients. This study aimed to assess if scheduled partial red cell exchanges impact pregnancy outcomes in sickle cell disease patients.

METHODS

Forty-seven pregnancies were divided into two groups based on whether patients received scheduled partial red cell exchanges. Collected data included demographics, laboratory values, number of hospital visits, and prenatal/perinatal/postnatal outcomes. Data were analyzed using descriptive statistics, t-test, Chi-square and Fisher's exact tests, and binary regression.

RESULTS

The mean age was 25.09 ± 4.39 years. Of 47 patients, 14 (29.8%) received scheduled red cell exchanges with 78.6% compliance with no evidence of alloimmunization. This procedure during pregnancy was associated with fewer admissions for pain crises (p=0.032), higher gestational age at delivery (p=0.007), and a lower incidence of neonatal intensive care admissions (p=0.011; odds ratio: 0.071; 95% confidence interval: 0.008-0.632). Logistic regression did not show any significant associations.

CONCLUSIONS

Sickle cell disease patients with complications in previous pregnancies, including high hospitalization/admission rates and preterm deliveries, could benefit from scheduled partial red cell exchanges or simple transfusions. Further research is needed to guide clinical practice pertaining to transfusional support in pregnant patients with sickle cell disease.

Migration of di(2-ethylhexyl) phthalate, diisononylcyclohexane-1,2-dicarboxylate and di(2-ethylhexyl) terephthalate from transfusion medical devices in labile blood products: A comparative study

BACKGROUND AND OBJECTIVES

Polyvinyl chloride (PVC) plasticized with di(2-ethylhexyl) phthalate (DEHP) is a widely used material for medical transfusion devices. Not covalently bound to PVC, DEHP can migrate into blood products during storage. Recognized as an endocrine disruptor and raising concerns about its potential carcinogenicity and reprotoxicity, DEHP is gradually being withdrawn from the medical device market. Therefore, the use of alternative plasticizers, such as diisononylcyclohexane-1,2-dicarboxylate (DINCH) and di(2-ethylhexyl) terephthalate (DEHT), as potential candidates for the replacement of DEHP in medical transfusion devices has been investigated. The purpose of this study was to evaluate the quantity of PVC-plasticizers in the blood components according to their preparation, storage conditions and in function of the plasticizer.

MATERIALS AND METHODS

Whole blood was collected, and labile blood products (LBPs) were prepared by the buffy-coat method with a PVC blood bag plasticized either with DEHP, DINCH or DEHT. DINCH and DEHT equivalent concentrations were quantified in LBPs by liquid chromatography-tandem mass spectrometry or coupled with UV and compared to DEHP equivalent concentrations.

RESULTS

The plasticizer equivalent concentration to which a patient is exposed during a transfusion depends on the preparation of LBPs as well as their storage conditions, that is, temperature and storage time. At day 1, for all LBPs, the migration of DEHP is 5.0 and 8.5 times greater than DINCH and DEHT, respectively. At the end of the 49 days storage period, the DEHP equivalent concentration in red blood cells concentrate is statistically higher when compared to DINCH and DEHT, with maximal values of 1.85, 1.13 and 0.86 μg/dm2 /mL, respectively.

CONCLUSION

In addition to lower toxicity, transfused patients using PVC-DEHT or PVC-DINCH blood bags are less exposed to plasticizers than using PVC-DEHP bags with a ranging exposure reduction from 38.9% to 87.3%, due to lower leachability into blood components.

Reconsidering sickle cell trait testing of red blood cell units allocated to children with sickle cell disease

BACKGROUND

Sickle cell trait (SCT) testing of red blood cell (RBC) units is sometimes performed to identify and divert units containing hemoglobin S (HbS). Recipients strategically guarded against this exposure include fetuses, neonates, and children with sickle cell disease (SCD). The clinical necessity of this practice is unclear.

STUDY DESIGN AND METHODS

A one-year audit (2018) was performed at a pediatric tertiary care hospital that tests for SCT in RBC units prescribed to children with SCD and neonates. The impact of incorporating varying numbers of SCT RBC units in a single-unit top-up, partial-manual red cell exchange, and automated erythrocytapheresis was modeled in four typical-parameter age scenarios (2, 5, 10, and 18 years) sharing a high baseline HbS. Additionally, a survey assessing SCT testing practices was administered to Canadian pediatric hospital transfusion laboratories serving hemoglobinopathy programs.

RESULTS

Of 2268 donor RBC units tested, one was positive for SCT (0.04% [95% CI: 0.01%-0.24%]), at a cost of $19,384.56 CAD. The impact of SCT unit incorporation on lost HbS reduction was modest (Δ1%-3% [automated erythrocytapheresis] and Δ4%-15% [top-up/partial manual exchange]). The survey (with all 13 sites responding) showed variable SCT testing practice; four (31%) do not test, four (31%) test for children with SCD, and six (46%) test for neonates.

CONCLUSION

RBC SCT testing may be more costly than beneficial or necessary in children with SCD. As of 2019, our transfusion service has ceased SCT testing for this population. Further research in the fetal/neonatal populations is needed to overturn this entrenched practice.

Increased Prevalence of Alloimmunization in Sickle Cell Disease? Should We Restore Blood Donation in French Guiana?

Patients with sickle cell disease often undergo frequent blood transfusions. This increases their exposure to red blood cell alloantigens of donor units, thus making it more likely that they produce alloantibodies. This cross-sectional study aimed to describe the prevalence of allo-immunization in patients with sickle cell disease who were monitored at Cayenne Hospital in 2016. Of the 451 patients recruited during the study period, 238 (52.8%) were female. There were 262 (58.1%) homozygous sickle cell and 151 (33.5%) compound heterozygous sickle cell patients. The median age of the participants was 23.09 years (range, 0.5–68). We noted different red blood cell extended phenotypes: -in the Duffy system, the Fy^a- Fy^b–profile was found in 299 patients (66%);—for the Kidd system, the most represented profile was Jka+ Jkb-, with 213 patients (47%). The Jka antigen was present in 355 patients;—in the MNS system, the S-s+ profile was found in 297 patients (66%);—the Lea antigen of the Lewis system was absent in 319 patients. The most frequent Rh phenotype in our patients was D+ C- E- c+ e+ K-, representing 51% of the patients. A total of 6,834 transfused packed red blood cell units were recorded. Sixty-eight patients (23%; 95% confidence interval, 20–25%) had detectable RBC alloantibodies. In multivariate logistic regression, only the mean number of single transfusions was statistically higher for the alloimmunized patients (p < 0.04). Thirteen (19%) of the patients with alloimmunization developed a delayed hemolytic transfusion reaction, thus representing 4.4% of the total number of transfused patients. Whether differences between donors from France vs. recipients from French Guiana could explain this high prevalence of alloimmunization to be examined. In conclusion, careful transfusion strategies for patients with RBC alloantibodies should allow further reduction of the rate of alloimmunization.

Hyperhaemolytic Syndrome in Sickle Cell Disease: Clearing the Cobwebs

Sickle cell disease (SCD) presents with a dynamic background of haemolysis and deepening anaemia. This increases the demand for transfusion if any additional strain on haemopoiesis is encountered due to any other physiological or pathological causes. Patients with cerebrovascular accidents are placed on chronic blood transfusion; those with acute sequestration and acute chest syndrome are likewise managed with blood transfusion. These patients are prone to develop complications of blood transfusion including alloimmunization and hyperhaemolytic syndrome (HHS). This term is used to describe haemolysis of both transfused and "own" red cells occurring during or post-transfusion in sickle cell patients. Hyperhaemolysis results in worsening post-transfusion haemoglobin due attendant haemolysis of both transfused and autologous red cells. The mechanism underlying this rare and usually fatal complication of SCD has been thought to be secondary to changes in the red cell membrane with associated immunological reactions against exposed cell membrane phospholipids. The predisposition to HHS in sickle cell is also varied and the search for a prediction pattern or value has been evasive. This review discusses the pathogenesis, risk factors and treatment of HHS, elaborating on what is known of this rare condition.

The molecular basis for the prothrombotic state in sickle cell disease

The genetic and molecular basis of sickle cell disease (SCD) has long since been characterized but the pathophysiological basis is not entirely defined. How a red cell hemolytic disorder initiates inflammation, endothelial dysfunction, coagulation activation and eventually leads to vascular thrombosis, is yet to be elucidated. Recent evidence has demonstrated a high frequency of unprovoked/recurrent venous thromboembolism (VTE) in SCD, with an increased risk of mortality among patients with a history of VTE. Here, we thoroughly review the molecular basis for the prothrombotic state in SCD, specifically highlighting emerging evidence for activation of overlapping inflammation and coagulation pathways, that predispose to venous thromboembolism. We share perspectives in managing venous thrombosis in SCD, highlighting innovative therapies with the potential to influence the clinical course of disease and reduce thrombotic risk, while maintaining an acceptable safety profile.

Blood Safety in SARS-CoV-2 Infection

: SARS-CoV-2 is a novel infectious agent that rapidly spread from a single city in China to all parts of the world. Right now, the world is facing a major pandemic crisis and every infected patient can infect the other two to three persons. The non-specific symptoms at the early stages of coronavirus 2019 (Covid-19) and also the presence of infected asymptomatic patients result in the absence of accurate estimation of infected patients. Although coronaviruses often affect the upper or lower respiratory tract, viral shedding in plasma or serum can occur and therefore, there is a theoretical risk regarding the transmission of these viruses by transfusion. Experience with other viruses from the corona family group (SARS-CoV and MERS-CoV) tells us that Covid-19 might have a significant impact on blood supply. Until now, SARS-CoV-2 has not been identified as a transfusion transmissible virus and viremia has only been diagnosed in serious patients who would not be allowed for blood donation. In this review article, the safety of blood products during the Covid-19 outbreak is discussed.

FcγR2B B2.4 haplotype predicts increased risk of red blood cell alloimmunization in sickle cell disease patients

BACKGROUND

Red blood cell (RBC) alloimmunization is an important transfusion complication which is prevalent among sickle cell disease (SCD) patients. Autoimmune diseases are a known risk factor for RBC alloimmunization, suggesting that autoimmunity and post-transfusion alloantibody development occur through similar physiopathological pathways. Polymorphisms in the FcγR2B gene have already been associated with several autoimmune disorders and hypothetically could be associated with RBC alloimmunization. Our goal was to evaluate if important polymorphisms of FcγR2B have an impact on the risk of RBC alloimmunization among SCD patients.

STUDY DESIGN AND METHODS

This was a case-control study in which alloimmunized and non-alloimmunized SCD patients were compared in terms of the genotype frequency of the FcγR2B polymorphisms -386G/C, -120 T/A, and 695C/T, genotyped through direct Sanger sequencing.

RESULTS

A total of 237 patients met the eligibility criteria, 120 cases (alloimmunized) and 117 controls (non-alloimmunized). RBC alloimmunization was associated with female sex (p < 0.001), lifetime number of RBC units transfused (p = 0.002) and 120 T/A FcγR2B genotype (p = 0.031). The FcγR2B promoter region haplotype 2B.4 (386C120A) was positively associated with RBC alloimunization (p = 0.045). The logistic regression (LR) model identified female sex (OR 10.03, CI 95% 5.16-19.49; p < 0.001) and FcγR2B 2B.4 haplotype (OR 4.55, CI95% 1.1118.65; p = 0.035) as independent predictors of RBC alloimmunization in SCD patients.

CONCLUSION

SCD patients with the FcγR2B 2B.4 haplotype had over a fourfold higher risk for RBC alloimmunization. This highlights the role played by FcγR2B on RBC alloimmunization and may be helpful in identifying the immune responders.

CN128: A New Orally Active Hydroxypyridinone Iron Chelator

Deferoxamine, deferiprone, and deferasirox are used for the treatment of systemic iron overload, although they possess limitations due to lack of oral activity, lower efficacy, and side effects. These limitations led to a search for an orally active iron chelator with an improved therapeutic index. The lower efficacy of deferiprone is due to rapid glucuronidation, leading to the formation of a nonchelating metabolite. Here, we demonstrate that the influence of metabolism can be reduced by introducing a sacrificial site for glucuronidation. A log P-guided investigation of 20 hydroxpyridinones led to the identification of CN128. The Fe(III) affinity and metal selectivity of CN128 are similar to those of deferiprone, the log P value is more lipophilic, and its iron scavenging ability is superior. Overall, CN128 was demonstrated to be safe in a range of toxicity assessments and is now in clinical trials for the treatment of β-thalassemia after regular blood transfusion.

American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support

BACKGROUND

Red cell transfusions remain a mainstay of therapy for patients with sickle cell disease (SCD), but pose significant clinical challenges. Guidance for specific indications and administration of transfusion, as well as screening, prevention, and management of alloimmunization, delayed hemolytic transfusion reactions (DHTRs), and iron overload may improve outcomes.

OBJECTIVE

Our objective was to develop evidence-based guidelines to support patients, clinicians, and other healthcare professionals in their decisions about transfusion support for SCD and the management of transfusion-related complications.

METHODS

The American Society of Hematology formed a multidisciplinary panel that was balanced to minimize bias from conflicts of interest and that included a patient representative. The panel prioritized clinical questions and outcomes. The Mayo Clinic Evidence-Based Practice Research Program supported the guideline development process. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to form recommendations, which were subject to public comment.

RESULTS

The panel developed 10 recommendations focused on red cell antigen typing and matching, indications, and mode of administration (simple vs red cell exchange), as well as screening, prevention, and management of alloimmunization, DHTRs, and iron overload.

CONCLUSIONS

The majority of panel recommendations were conditional due to the paucity of direct, high-certainty evidence for outcomes of interest. Research priorities were identified, including prospective studies to understand the role of serologic vs genotypic red cell matching, the mechanism of HTRs resulting from specific alloantigens to inform therapy, the role and timing of regular transfusions during pregnancy for women, and the optimal treatment of transfusional iron overload in SCD.

Red blood cell exchange in patients with sickle cell disease-indications and management: a review and consensus report by the therapeutic apheresis subsection of the AABB

BACKGROUND

A prior practice survey revealed variations in the management of patients with sickle cell disease (SCD) and stressed the need for comprehensive guidelines. Here we discuss: 1) common indications for red blood cell exchange (RCE), 2) options for access, 3) how to prepare the red blood cells (RBCs) to be used for RCE, 4) target hemoglobin (Hb) and/or hematocrit (Hct) and HbS level, 5) RBC depletion/RCE, and 6) some complications that may ensue.

STUDY DESIGN AND METHODS

Fifteen physicians actively practicing apheresis from 14 institutions representing different areas within the United States discussed how they manage RCE for patients with SCD.

RESULTS

Simple transfusion is recommended to treat symptomatic anemia with Hb level of less than 9 g/dL. RCE is indicated to prevent or treat complications arising from the presence of HbS. The most important goals are reduction of HbS while also preventing hyperviscosity. The usual goals are a target HbS level of not more than 30% and Hct level of less than 30%.

CONCLUSION

Although a consensus as to protocol details may not be possible, there are areas of agreement in the management of these patients, for example, that it is optimal to avoid hyperviscosity and iron overload, that a target Hb S level in the range of 30% is generally desirable, and that RCE as an acute treatment for pain crisis in the absence of other acute or chronic conditions is ordinarily discouraged.

Importance of extended blood group genotyping in multiply transfused patients

Blood group antigen systems are not limited to the ABO blood groups. There is increasing interest in the detection of extended blood group systems on the red cell surface. The conventional method used to determine extended blood group antigens or red cell phenotype is by serological testing, which is based on the detection of visible haemagglutination or the presence of haemolysis. However, this technique has many limitations due to recent exposure to donor red cell, certain drugs or medications or other diseases that may alter the red cell membrane. We aimed to determine the red cell blood group genotype by SNP real time PCR and to compare the results with the conventional serological methods in multiply transfused patients. Sixty-three patients participated in this study whose peripheral blood was collected and blood group phenotype was determined by serological tube method while the genotype was performed using TaqMan^® Single Nucleotide Polymorphism (SNP) RT-PCR assays for RHEe, RHCc, Kidd and Duffy blood group systems. Discrepancies were found between the phenotype and genotype results for all blood groups tested. Accurate red blood cell antigen profiling is important for patients requiring multiple transfusions. The SNP RT-PCR platform is a reliable alternative to the conventional method.

Transfusion Therapy in Children With Sickle Cell Disease

Hydroxyurea, blood transfusions, and hematopoietic stem cell transplantation represent the 3 disease-modifying therapies in children with sickle cell disease (SCD). Blood transfusions play an increasingly important role in both prevention and management of SCD complications in this age group. This review will focus on the indications of blood transfusion in children with SCD and modalities of its administration. It will also highlight the complications of this life-saving therapy and ways of optimizing transfusion to minimize its associated risks.

Alloimmunization in Patients with Sickle Cell Disease and Thalassemia: Experience of a Single Centre in Oman

Background

Blood transfusion is an integral part of the supportive care for patients with sickle cell disease (SCD) and thalassaemia. The hazard of red cell alloimmunization, however, is one of the main complications of this therapy.

Objectives

The aim of this study was to evaluate the prevalence of red cell alloimmunization in Omani patients with sickle cell anaemia and thalassemia.

Methods

This study included 262 patients whose historical transfusion records were available. One hundred and twenty-nine patients with thalassaemia who were attending the day care unit for regular transfusions, and 133 SCD patients admitted at our hospital were included in this study. The Diamed® gel system was used for the screening and identification of atypical antibodies.

Results

The rate of alloimmunization in SCD patients was 31.6% (n=42, 95%CI, 24.87–40.66), whereas in patients with thalassaemia it was 20% (n=26; 95%CI, 13.9–27.6). Antibodies to E, e, C, c, D, K, S, Fyª, Kpª, Jkª and C^w were observed; 85% of the patients were also immunised with Rh and Kell antigens. Considering the two groups together, 8 developed nonspecific antibodies and 12 developed more than one antibody.

Conclusions

Red cell transfusions were associated with a significant risk of alloimmunization. It is, therefore, imperative to perform an initial extended red cell phenotyping for both donors and recipients, and carefully select ABO, Rh and Kell matched donors. The higher incidence of alloimmunization in SCD patients is related to the inherent SCD-specific inflammatory state.

Sickle Cell Disease and Acute Chest Syndrome: Epidemiology, Diagnosis, Management, Outcomes

Sickle cell disease (SCD) is one of the most common monogenetic diseases worldwide and is attributable to significant morbidity and mortality. Mutations causing abnormal hemoglobin formation in this disease lead to structural abnormalities and cumulative damage to the cellular membrane of sickled erythrocytes. Polymerization and aggregation of these cells within the microvasculature results in severe vaso-occlusive pain crisis, chronic hemolytic anemia, and multiorgan pathology in patients. Pulmonary manifestations of SCD, including the acute chest syndrome (ACS), are a leading cause of hospitalization and mortality. ACS is a severe type of acute lung injury, defined as the development of a new pulmonary infiltrate, involving at least one complete lung segment, that is accompanied by fever, chest pain, tachypnea, wheezing, or cough in a patient with SCD. The etiology of ACS is multifactorial, with the most common mechanisms including infection, fat and bone marrow embolism, and direct microvascular vaso-occlusion. Despite recent advances in our understanding of the pathogenesis and clinical management of ACS in SCD, patient outcomes remain unacceptably poor. This chapter reviews the epidemiology, diagnosis, management, and outcomes of ACS in SCD. Proper screening, a high index of clinical suspicion, and immediate clinical care for this condition are pivotal for improving patient outcomes.

Immune Regulation of sickle Cell Alloimmunization

Red blood cell (RBC) transfusion remains an important treatment for patients with sickle cell disease (SCD) and the majority of patients receive transfusions by adulthood. However, SCD patients are at a high risk of alloimmunization, which can cause life-threatening complications. The high rate of alloimmunization can in part be explained by chronic inflammatory condition in SCD characterized by significant immune and inflammatory activation. Heightened immune effector cell responses and/or impaired regulatory networks are likely to drive alloantibody production in alloimmunized SCD patients. In support of this, altered T cell immunoregulation, known to control antibody responses, have been reported in alloimmunized SCD patients. In addition, stronger follicular help T cell responses that help antibody production by B cells were described in alloimmunized as compared to non-alloimmunized SCD patients. Furthermore, several innate immune abnormalities have been identified in alloimmunized SCD patients, including a compromised anti-inflammatory response against extracellular cell free heme. The data support a model in which alloimmunized SCD patients are unable to switch off their proinflammatory state in response to the ongoing hemolytic state characteristic of SCD, placing this patient subset at a higher risk to develop a strong immune response against allogeneic determinants on transfused RBCs, thus increasing the risk of further alloimmunization. A detailed mechanistic understanding of innate immune abnormalities that can contribute to pathogenic T cell responses in alloimmunized SCD patients will lay the foundation for identification of biomarkers of alloimmunization with the goal that this information will ultimately help guide therapy in these patients.

Use of Cellular and Plasma Apheresis in the Critically Ill Patient: Part II: Clinical Indications and Applications

Apheresis is the process of separating the blood and removing or manipulating a cellular or plasma component for therapeutic benefit. Such procedures may be indicated in the critical care setting as primary or adjunctive therapy for certain hematologic, neurologic, renal, and autoimmune/rheumatologic disorders. In part I of this series, the technical aspects of apheresis were described and the physiologic rationale and clinical considerations were discussed. This review highlights the pathophysiologic basis, specific clinical indications, and treatment parameters for disorders that more commonly require management in the intensive care unit. The choice of plasma or cellular apheresis in these cases is guided by wellaccepted, evidence-based clinical treatment guidelines. For some disorders, such as liver failure, severe sepsis, and multiple-organ dysfunction syndrome, apheresis treatment approaches remain experimental. Ongoing studies are investigating the potential utility of conventional plasma exchange, ex vivo plasma manipulation, and newer technologies for these and other disorders in severely ill patients.

Implementation of a Process for Initial Transcranial Doppler Ultrasonography in Children With Sickle Cell Anemia

Stroke, a devastating complication of sickle cell anemia (SCA), can cause irreversible brain injury with physical and cognitive deficits. Transcranial Doppler ultrasonography (TCD) is a non-invasive tool for identifying children with SCA at highest risk of stroke. National guidelines recommend that TCD screening begin at age 2 years, yet there is research to suggest less than half of young children undergo screening. The purpose of this project was to use quality improvement methods to improve the proportion of patients aged 24-27 months who successfully completed their initial TCD from 25% to 75% by December 31, 2013. Quality improvement methods (e.g., process mapping, simplified failure mode effect analysis, and plan-do-study-act cycles) were used to develop and test processes for identifying eligible patients, scheduling TCDs, preparing children and families for the first TCD, and monitoring outcomes (i.e., TCD protocol). Progress was tracked using a report of eligible patients and a chart showing the age in months for the first successful TCD (population metric). As of December 2013, 100% of eligible patients successfully completed their initial TCD screen; this improvement was maintained for the next 20 months. In November 2014, a Welch's one-way ANOVA was conducted. Results showed a statistically significant difference between the average age of first TCD for eligible patients born in 2009 and eligible patients born during the intervention period (2010-2013; F[1,11.712]=16.03, p=0.002). Use of quality improvement methods to implement a TCD protocol was associated with improved TCD screening rates in young children with SCA.

Anti-HI can cause a severe delayed hemolytic transfusion reaction with hyperhemolysis in sickle cell disease patients

BACKGROUND

Delayed hemolytic transfusion reaction (DHTR) is a life-threatening condition in sickle cell disease (SCD) patients that is frequently complicated by hyperhemolysis. Antibodies resulting from antigen disparity between donors of European ancestry and patients of African ancestry are common, but situations involving antibodies not classically of clinical significance are also encountered. Anti-HI is generally considered to be an innocuous naturally occurring antibody.

STUDY DESIGN AND METHODS

We describe two cases of hyperhemolysis with anti-HI and provide details of the reported cases.

RESULTS

Both SCD patients were polyimmunized and belonged to blood group B. They developed anti-HI that was reactive at 37°C, after the transfusion of group O red blood cell units matched for all known and produced antibodies classically considered to be clinically significant. Both patients developed DHTR with hyperhemolysis. In the first case, a pregnant woman, a second transfusion was unavoidable and the patient died from cardiac arrest. The state of the second patient improved without the need for further transfusion.

CONCLUSION

Three other cases of DHTR with anti-HI have been described in the literature in SCD patients. The two additional cases reported here definitively demonstrate that anti-HI is dangerous in SCD patients. As a result, ABO-identical matching (including A1 status) must be considered in SCD patients with anti-HI.

Protective effect of HLA-DQB1 alleles against alloimmunization in patients with sickle cell disease

BACKGROUND

Alloimmunization or the development of alloantibodies to Red Blood Cell (RBC) antigens is considered one of the major complications after RBC transfusions in patients with sickle cell disease (SCD) and can lead to both acute and delayed hemolytic reactions. It has been suggested that polymorphisms in HLA genes, may play a role in alloimmunization. We conducted a retrospective study analyzing the influence of HLA-DRB1 and DQB1 genetic diversity on RBC-alloimmunization.

STUDY DESIGN

Two-hundred four multi-transfused SCD patients with and without RBC-alloimmunization were typed at low/medium resolution by PCR-SSO, using IMGT-HLA Database. HLA-DRB1 and DQB1 allele frequencies were analyzed using logistic regression models, and global p-value was calculated using multiple logistic regression.

RESULTS

While only trends towards associations between HLA-DR diversity and alloimmunization were observed, analysis of HLA-DQ showed that HLA-DQ2 (p=0.02), -DQ3 (p=0.02) and -DQ5 (p=0.01) alleles were significantly higher in non-alloimmunized patients, likely behaving as protective alleles. In addition, multiple logistic regression analysis showed both HLA-DQ2/6 (p=0.01) and HLA-DQ5/5 (p=0.03) combinations constitute additional predictor of protective status.

CONCLUSION

Our data suggest that particular HLA-DQ alleles influence the clinical course of RBC transfusion in patients with SCD, which could pave the way towards predictive strategies.

Pierre T, Heeney MM, Schultz WH, Davis BR, Ware RE. Liver iron concentration measurements by MRI in chronically transfused children with sickle cell anemia: baseline results from the TWiTCH trial

Noninvasive, quantitative, and accurate assessment of liver iron concentration (LIC) by MRI is useful for patients receiving transfusions, but R2 and R2* MRI techniques have not been systematically compared in sickle cell anemia (SCA). We report baseline LIC results from the TWiTCH trial, which compares hydroxyurea with blood transfusion treatment for primary stroke prophylaxis assessed by transcranial Doppler sonography in pediatric SCA patients. Liver R2 was collected and processed using a FDA-approved commercial process (FerriScan®), while liver R2* quality control and processing were performed by a Core Laboratory blinded to clinical site and patient data. Baseline LIC studies using both MRI techniques were available for 120 participants. LICR2* and LICR2 results were highly correlated (r(2)  = 0.93). A proportional bias of LIC(R2*)/LIC(R2), decreasing with average LIC, was observed. Systematic differences between LICR2* and LICR2 were also observed by MRI manufacturer. Importantly, LICR2* and LICR2 estimates had broad 95% limits of agreement with respect to each other. We recommend LICR2 and LICR2* not be used interchangeably in SCA patients to follow individual patient trends in iron burden.

Blood transfusion and 30-day readmission rate in adult patients hospitalized with sickle cell disease crisis

BACKGROUND

Sickle cell disease (SCD) patients hospitalized with vasoocclusive pain crisis tend to have prolonged length of stay (LOS) and high 30-day readmission rates. We investigated the associations of demographic characteristics, comorbidities, and blood transfusion during hospitalization with these outcomes.

STUDY DESIGN AND METHODS

Repeated regression analysis was used to analyze 39,324 admissions of 4348 adults with sickle cell crisis from 2007 to 2012 in the Truven Health MarketScan Medicaid Databases.

RESULTS

The mean (95% range) LOS was 5.9 (1.0-19.0) days and the 30-day readmission rate was 39.6% (95% confidence interval [CI], 39.1%-40.0%). Older age; chronic cardiopulmonary, renal, or liver disease; and sepsis were associated with both longer LOS and greater 30-day readmission rate. Female sex, iron overload, acute chest syndrome, acute renal failure, and stroke were additional predictors of longer LOS. Simple red blood cell transfusion was administered in 31.8% of the admissions, and these patients tended to have more severe disease (chronic cardiopulmonary or kidney disease, acute chest syndrome, acute kidney or liver failure, sepsis). Nevertheless, transfusion was associated with a reduced estimated odds ratio (OR) of inpatient mortality of 0.75 (95% CI, 0.57-0.99) and a decreased OR of 30-day readmission of 0.78 (95% CI, 0.73-0.83).

CONCLUSION

Our findings point to blood transfusion as a potential means to reduce the 30-day readmission rate among Medicaid patients hospitalized with sickle cell crisis. There is a need for a prospective study to examine the potential benefit and safety of simple blood transfusion for this purpose.

Mechanisms of sickle cell alloimmunization

Red blood cell (RBC) alloimmunization can be a life-threatening complication for patients with sickle cell disease (SCD) receiving therapeutic transfusions. Despite provision of extended antigen-matched donor RBCs, patients continue to develop antibodies due to high degree of polymorphisms in the immunogenic antigens in individuals of African ancestry. Identification of biomarkers of alloimmunization in this patient population is therefore of great interest and will help to identify in advance patients most likely to make antibodies in response to transfusion. We have recently identified altered T cell responses and innate immune abnormalities in alloimmunized SCD patients. In this paper, we summarize this work and propose our working model of how innate immune abnormalities can contribute to pathogenic T cell responses in alloimmunized SCD patients. We believe that unravelling the basis of such altered interactions at the cellular and molecular level will help future identification of biomarkers of alloimmunization with the goal that this information will ultimately help guide therapy in these patients.

Transfusional iron overload and iron chelation therapy in thalassemia major and sickle cell disease

Iron overload is an inevitable consequence of blood transfusions and is often accompanied by increased iron absorption from the gut. Chelation therapy is necessary to prevent the consequences of hemosiderosis. Three chelators, deferoxamine, deferiprone, and deferasirox, are presently available and a fourth is undergoing clinical trials. The efficacy of all 3 available chelators has been demonstrated. Also, many studies have shown the efficacy of the combination of deferoxamine plus deferiprone as an intensive treatment of severe iron overload. Alternating chelators can reduce adverse effects and improve compliance. Adherence to therapy is crucial for good results.

Alloimmunization in patients with sickle cell disease in French Guiana

This study in French Guiana assessed the frequency of alloimmunization to red cell antigens in sickle cell disease patients over 1995–2011 and identified the most common antibodies. A retrospective analysis of the transfusion history and medical records of 302 patients showed that 29/178 transfused patients had developed alloantibodies (16%). The most frequent alloantibodies were anti-LE1, anti-MNS1, anti-LE2, and anti-FY1 and were developed after transfusion of standard red cell units. The frequency of the clinically significant antibodies in this population of SCD patients was 11% (19/178). The antibodies found on those patients who had delayed hemolytic transfusion reaction were anti-K1, anti-FY1, and anti-MNS3. The strategies used to decrease alloimmunization in French Guiana are discussed.

Deferitazole, a new orally active iron chelator

Deferitazole possesses a high affinity and selectivity for iron(iii), forming an equilibrium mixture of two Fe^III(deferitazole)₂complexes, under biological conditions.

Alloimmunization in sickle cell anemia in the era of extended red cell typing

BACKGROUND

Red blood cell (RBC) transfusion remains an essential part of the management of patients with sickle cell disease (SCD). Alloimmunization is a major complication of transfusions. Extended RBC typing is advocated as a means to reduce alloimmunization in SCD. Our goal was to assess alloimmunization among individuals with SCD at our center since implementing extended RBC typing.

MATERIALS AND METHODS

We reviewed electronic medical records of all patients with SCD (N = 641) in our comprehensive SCD Program to determine transfusion histories. Cross-referencing with our blood bank database, we extracted data such as antibodies identified, detection date and genotyping in specific cases. Transfusion sources were determined for those with C, E, and Kell antibodies.

RESULTS

Of 180 patients transfused from 2002 to 2011, 26 developed at least one new antibody. The majority of alloimmunized patients (14/26) received episodic transfusions only. The most common antibodies formed were against C and E antigens. Of the 16 patients who developed C, E, Kell antibodies, nine had one or more documented transfusions at an outside hospital. Five patients had Rh variants undetectable on routine phenotyping including two novel e alleles related to ceAR and ce(S)(733G).

CONCLUSION

Despite extended RBC typing, alloimmunization may still occur due to RBC variants that are not detected on routine screening and transfusions at institutions where extended RBC typing is not done. Extended RBC typing should be the standard of care for patients with SCD. Prospective genotyping may reduce allosensitization to rare variants not detected on routine screening.

Regulatory B-cell compartment in transfused alloimmunized and non-alloimmunized patients with sickle cell disease

Transfusion therapy is a life-sustaining treatment for patients with sickle cell disease (SCD), but can cause serious complications including alloimmunization. We previously reported diminished regulatory T cells (Tregs) and skewed Th2 responses in alloimmunized SCD patients. We hypothesized that the B cell regulatory (Breg) compartment, which controls Treg and Th differentiation, may also be compromised in allosensitized SCD patients. Phenotypically, we did not find differences in the frequency or numbers of CD24(hi) CD38(hi) and CD24(hi) CD27(+) B cell subsets, both previously identified as human Bregs, between alloimmunized and non-alloimmunized SCD patients on regular transfusions. However, at the functional level, CD19+ B cells from alloimmunized SCD patients expressed lower levels of IL-10 following stimulation as compared with non-alloimmunized patients (P < 0.05), and had reduced ability in inhibiting autologous CD14+ monocyte TNF-α expression (P < 0.05). These findings suggest that Bregs from alloimmunized and non-alloimmunized SCD patients differ in their ability to produce IL-10 and dampen monocyte activation, all consistent with an altered immunoregulatory state in alloimmunized SCD patients.

[Red blood cell immunization in haemoglobinopathie: about 84 cases]

AIMS

To estimate the rate of red cell immunization in hemoglobinopathies.

PATIENTS AND METHODS

Prospective study (1990-2009) about 84 patients: 44 homozygous sickle cell anemia, one heterozygous sickle cell anemia S/C, 30 thalassemia and nine sickle cell anemia-thalassemia. The mean age was 10.13 years (extremes: 1-45). The red cell units transfused were ABORH1 compatible, then RH-KELL phenotyped after 2006 and phenocompatible after alloimmunisation. The cross-match was realized using indirect antiglobuline test. Irregular red cell antibody screening was realized before every transfusional episode and the direct antiglobuline test was done when there was a poor transfusional efficiency.

RESULTS

The number of red blood cells units transfused was 3545 (42.2/patient). The number of red cell antibody screening and the number of direct antiglobulin test were respectively 1474 (17.5/patient) and 272 (3.2/patient). Twenty-seven antibodies were identified (32.1%): 14 alloantibodies (16.6%, 16.6% in sickle cell disease, 16.6% in thalassemia, P=1), 16 antoantibodies (19.04%, 11.1% in sickle cell disease, 33.3% in thalassemia, P=0.018). There were three cases of association of allo- and autoantibodies. The most frequent alloantibodies were anti-RH3 and anti-KEL1 and were developed after transfusion of standard red cell units. There was no significant relation, neither between sex and risk of immunization, nor between the number of red cell units transfused and alloimmunization. On the other hand, there was a significant relation between autoimmunization and the number of red cell units transfused in thalassemia (P<0.001).

CONCLUSION

This study proves the interest of using RH-KELL red cell units compatible in patients with hemoglobinopathies in order to reduce alloimmunisation rates.

Challenges of alloimmunization in patients with haemoglobinopathies

Red blood cell (RBC) transfusions can be life-sustaining in chronic inherited anaemias, such as thalassaemia, and the indications for blood transfusions in patients with sickle cell disease continue to expand. Complications of transfusions, such as allosensitization, can create significant medical challenges in the management of patients with haemoglobinopathies. This review summarizes key findings from the medical literature related to alloimmunization in haemoglobinopathies and examines potential measures to mitigate these risks. Areas where future studies are needed are also addressed.

Frequency of red cell alloimmunization in patients with sickle cell anemia in an Egyptian referral hospital

INTRODUCTION

Sickle cell anemia (SCA) is an important public health issue in Tanta, Egypt. Erythrocyte transfusions may reduce the morbidity of SCA, however, they are associated with numerous risks. Among other risk categories, alloimmunization to red cell antigens may result from transfusions. The objective of this study was to explore the frequency of red cell alloantibodies among SCA patients who received regular transfusions.

MATERIALS AND METHODS

A total of 42 patients with SCA were included in this study. This work planned to study the presence of alloantibodies to different red cell antigens in multi-transfused SCA patients using the ID card micro-typing system. Clinical and laboratory data were collected and analyzed to find out the frequency, pattern and factors influencing red cell alloimmunization secondary to multiple blood transfusion in these patients.

RESULTS

Of a total of 42 SCA patients included in the study, 21.4% of patients developed alloantibodies. The most common alloantibodies were anti-K, anti-E and anti-C. The rate of incidence of these alloantibodies was 7.1%, 4.8% and 4.8%, respectively. There was significant association between alloantibody and the rate of transfused blood. The mean age of patients with and without alloimmunization was 12.0 and 6.2 years.

CONCLUSIONS

Alloimmunization to minor erythrocyte antigens of variable clinical significance is a frequent finding in transfused SCA patients. Regular screening for red cell alloantibodies would provide better management of these patients.

Substituent effects on desferrithiocin and desferrithiocin analogue iron-clearing and toxicity profiles

Desferrithiocin (DFT, 1) is a very efficient iron chelator when given orally. However, it is severely nephrotoxic. Structure-activity studies with 1 demonstrated that removal of the aromatic nitrogen to provide desazadesferrithiocin (DADFT, 2) and introduction of either a hydroxyl group or a polyether fragment onto the aromatic ring resulted in orally active iron chelators that were much less toxic than 1. The purpose of the current study was to determine if a comparable reduction in renal toxicity could be achieved by performing the same structural manipulations on 1 itself. Accordingly, three DFT analogues were synthesized. The iron-clearing efficiency and ferrokinetics were evaluated in rats and primates; toxicity assessments were carried out in rodents. The resulting DFT ligands demonstrated a reduction in toxicity that was equivalent to that of the DADFT analogues and presented with excellent iron-clearing properties.

Indications and complications of transfusions in sickle cell disease

Red cell transfusion remains an important part of the management of acute and chronic complications in SCD. The ongoing and emerging uses of transfusions in SCD may have significant benefits; however, the potential complications of transfusions also deserve careful consideration. In this report we review current indications for transfusions, transfusion complications, modifications of transfusion practices to mitigate risk, and potential considerations to improve transfusion outcomes.