Red cell exchange for patients with sickle cell disease: an international survey of current practices

CDDO-Imidazole regulates RBC alloimmunization to the KEL antigen by activating Nrf2

During red blood cell (RBC) transfusion, production of alloantibodies can promote significant hemolytic events. However, most transfusion recipients do not form anti-RBC alloantibodies. Identifying mechanisms that inhibit alloimmunization may lead to prophylactic interventions. One potential regulatory mechanism is activation of the transcription factor, nuclear factor erythroid-derived 2-like 2 (Nrf2), a master regulatory of antioxidant pathways. Pharmacologic Nrf2 activators improve sequelae of sickle cell disease in pre-clinical models. The Nrf2 activator, 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), suppresses production of inflammatory cytokines including type 1 interferons (IFNα/β), which have been implicated in promoting RBC alloimmunization in transfusion models. Thus, we tested the hypothesis that the Nrf2 activator, CDDO-Im, regulates RBC alloimmunization. Here, we report that CDDO-Im induced Nrf2 activated gene expression and suppressed poly(I:C)-induced IFNα/β-stimulated gene (ISG) expression in human macrophages and murine blood leukocytes. In addition, following transfusion of wildtype mice with RBCs expressing the KEL antigen, CDDO-Im treatment inhibited poly(I:C)-induced anti-KEL IgG production and promoted post-transfusion recovery of KEL+ RBCs, but failed to do so in Nrf2 -/- mice. Results indicate that activation of the Nrf2 antioxidant pathway regulates RBC alloimmunization to the KEL antigen in a pre-clinical model. If findings translate to other models and human studies, Nrf2 activators may represent a potential prophylactic intervention to inhibit alloimmunization.

Key Points

The antioxidant pathway, Nrf2, inhibits anti-RBC alloantibody responses in a pre-clinical transfusion model.Nrf2 activation may represent a prophylactic strategy to inhibit RBC alloimmunization in transfusion recipients.

Red blood cell utilization in patients with sickle cell disease: A Canadian single-center experience

BACKGROUND

Red blood cell (RBC) utilization in patients with sickle cell disease (SCD) in Canada is poorly defined. This study describes RBC utilization in an SCD cohort at a single Canadian center.

STUDY DESIGN AND METHODS

All adults with SCD who received care at the Ottawa Hospital between January 2006 and May 2019 were included, and followed until December 2021. Data on hospital encounters and RBC transfusions were obtained from hospital databases.

RESULTS

Overall, 273 patients were included (median age: 25 years; 53.8% female; median follow-up: 8.1 years). During the study period, there were 23,127 hospital encounters (median: 45 [interquartile range (IQR) 18, 100] per patient), with 165 patients (60.4% of cohort) receiving 22,538 RBC units. Most RBC units (86.5%) were transfused in the outpatient setting. Although only 2.9% of patients had O-negative blood type, O-negative RBC units accounted for 29.1% of units transfused. One hundred forty-seven patients received 2205 RBC units (9.8% of total) as simple transfusions (median: 5 [IQR 3, 13] per patient), and 88 patients received 20,333 RBC units (90.2% of total) during 2702 red cell exchange (RCE) sessions (median: 14.5 (IQR 1, 47.5) RCE per transfused patient). A median of 7 RBC units (IQR 6, 9) were transfused per RCE session, with a median of 30 days (IQR 28, 40) between sessions.

DISCUSSION

Patients with SCD at our center frequently received O-negative units, and large RBC volumes were used for RCE. These results provide a utilization baseline for future education and quality improvement initiatives to optimize RBC stewardship.

Use of automated isovolemic hemodilution red-cell exchange in patients with sickle cell disease: A Canadian single center experience

BACKGROUND

Red cell exchange (RCE) is an important treatment for sickle cell disease (SCD). It is a resource-intensive intervention requiring large volumes of red blood cells (RBC), which are frequently antigen-matched. Efforts to reduce the volume of units transfused, while maintaining treatment efficacy is an important need. This study evaluates the impact of a change to isovolemic hemodilution (IHD)-RCE on RBC utilization in SCD patients at a Canadian center.

STUDY DESIGN AND METHODS

Adult SCD patients receiving chronic automated RCE at the Ottawa Hospital were approached for study inclusion. To safely attain a meaningful reduction in transfused RBCs, RCE parameters were individualized for each patient. IHD-RCE was performed only if an estimated reduction in RBC volume of at least 200 mL was expected, with hematocrit not allowed to decrease below 20%. Data were compared in the 6-months before and after the protocol change.

RESULTS

Twenty-two adult patients met the criteria for inclusion. There was a net reduction of 107 RBC units after the transition from standard RCE to IHD-RCE (1035 vs. 928 units; -10.3%). The mean number of RBC units transfused per patient decreased by 4.8 (47.0 vs. 42.2 units; p = .01). No difference in target post-RCE hemoglobin S levels was observed.

DISCUSSION

In this study IHD-RCE reduced RBC utilization without impacting efficacy or safety, conserving 107 RBC units (an annualized savings of $95,444 CAD). No adverse events due to saline replacement were observed. Increased awareness of the benefits of IHD-RCE through knowledge translation could promote greater uptake.

Post-exchange neutrophil count, but not post-hematocrit, predicts endogenous erythropoiesis in patients with sickle cell disease undergoing chronic red cell exchange

BACKGROUND

With chronic transfusion in sickle cell disease (SCD), equipoise exists regarding whether increasing the post-procedure hematocrit (Hct) suppresses endogenous erythropoiesis. Reticulocytosis predicts SCD morbidity and mortality, so this study's objective was to clarify the role of the post-procedure Hct in suppressing reticulocytosis and to identify other potential red cell exchange (RCE) parameters predictive of reticulocytosis.

STUDY DESIGN AND METHODS

This retrospective analysis of 17 patients who underwent chronic RCE at a single institution between 2014 and 2022 examined both standard red cell exchanges (SRCE) and exchanges preceded by isovolemic hemodilution (IVH-RCE). Post-procedure parameters with biologic plausibility to influence the subsequent procedure's absolute reticulocyte count (sPre-ARC) were examined using regression modeling.

RESULTS

Neither post-hematocrit, nor post-hemoglobin (Hb), nor ΔHb/day was associated with sPre-ARC or the change in HbS% per day (ΔHbS%/day). Concurrent Hb was predictive for SRCE but not IVH-RCE, where ARC trended lower than with SRCE. Male gender and post-procedure neutrophil and white cell counts were predictors of sPre-ARC, consistent with their associations with SCD morbidity and mortality. IVH-RCE had a stronger correlation than standard RCE between pre-Hct and neutrophil or white cell depletion.

DISCUSSION

Although targeting a post-procedure Hct maintains a higher subsequent pre-procedure Hb and a lower sPre-HbS%, it does not lead to sustained suppression of reticulocytosis as measured by the sPre-ARC or the ΔHbS%/day. IVH-RCE or the addition of hydroxyurea could be considered in those patients with high reticulocyte, white blood cell, or neutrophil counts.

Development of a Uniform Apheresis Case Report Form for Standardized Collection of Apheresis Data

Apheresis is performed worldwide for an increasing number of indications. The development of common data elements (CDE) for apheresis related areas may facilitate conduct of new research, enhance quality initiatives including benchmarking, and improve patient care. This report describes the systematic development of the Uniform Apheresis Case Report Form (UACRF) as part of the Apheresis in the United States (ApheresUS) program. A consensus panel of 17 diverse experts in apheresis, related specialties, and electronic case report form (eCRF), and database development was assembled. The panel met via online conferencing from November 17, 2020 to December 1, 2021. A draft document was posted online for public comment from October 11, 2021 to November 10, 2021. Feedback was collected using an online survey tool. The consensus panel revised the UACRF. This version was converted to an eCRF with additional changes made to improve usability in this format. The final version of the UACRF was created on August 24, 2023. The UACRF contains 16 modules: procedure and subject eligibility, patient demographics, general procedure information, laboratory parameters, vascular access, common procedure elements, eight procedure specific modules (mononuclear cell collection and seven therapeutic modalities), outcomes, and site information. A total of 137 data elements were created, including 57 with one or more subelements. The UACRF is the first systematic attempt to develop CDE for therapeutic apheresis and white blood cell collections. Further validation of the UACRF is necessary to confirm the tool's ability to collect the relevant data elements and determine the usability of the form.

Chronic automated red cell exchange therapy for sickle cell disease

BACKGROUND

The data to support chronic automated red cell exchange (RCE) in sickle cell disease (SCD) outside of stroke prevention, is limited, especially in adults.

STUDY DESIGN AND METHODS

A retrospective analysis was conducted of patients with SCD who were referred for chronic RCE at our institution over a 10-year period. Data that were evaluated included patient demographics, referral indications, and procedural details (e.g., vascular access, adverse events, etc.). In a subanalysis, the number of annual acute care encounters during 3 years of chronic RCE was compared with that in the year preceding the first RCE.

RESULTS

A total of 164 patients were referred for chronic RCE: median age was 28 years (interquartile range [IQR] = 22-36) at referral and 60% were female. Seventy (42.6%) were naïve to chronic transfusion (simple or RCE) prior to referral. The leading indications for referral were refractory pain (73/164, 44.5%) and iron overload (57/164, 34.7%). A total of 5090 procedures occurred during the study period (median = 19, IQR = 5-45). Of the 138 patients who had central vascular access, 8 (6%) and 16 (12%) had ≥1 central-line-related thrombosis and/or infection, respectively. Of those who were not RBC alloimmunized at initiation of RCE, 12/105 (11.4%) developed new antibodies during chronic RCE. In those 30 patients who were adherent to therapy for 3 years, there was no significant difference in acute care encounters following initiation of RCE.

CONCLUSION

Prospective clinical trials are needed to determine which patients are most likely to benefit from chronic RCE and refine selection accordingly.

Optimization of single-needle red cell exchange in patients with sickle cell disease

The hypercoagulable state associated with sickle cell disease (SCD) can be challenging for apheresis procedures. Among 62 single-needle red cell exchanges (SN-RCEs) performed over a 15-month period, 4 patients experienced 6 hemolytic events with a discolored plasma layer, elevated plasma/RBC interface in the centrifuge, and accompanying alarms of "Cells were detected in plasma line from centrifuge" or "AIM system detected RBC at top of connector." The hemolysis originated from the apheresis instrument because samples from the apheresis belt but not the patients' peripheral blood were positive for hemolysis. Further analysis showed the alarms occurred more often in SN-RCEs (20.4%) than double-needle RCEs (2.7%), and the hemolysis was probably secondary to clumping. To optimize SN-RCE, we increased the anticoagulant dosage by changing Inlet/AC ratio from 13 to 8 and lowered the inlet rate to the level comparable to double-needle RCE. The adjustments were well-tolerated with no more hemolysis.

Eleven years of alloimmunization in 6496 patients with sickle cell disease in France who received transfusion

ABSTRACT

Red blood cell (RBC) transfusion is a major therapy for sickle cell disease (SCD). Patients are at risk of forming antibodies to RBC antigens, which can result in the impossibility to find compatible units and can cause hemolytic transfusion reactions. This retrospective study investigates the evolution of RBC consumption and the frequencies, specificities, and chronology of the appearance of antibodies in a population of patients consistently receiving RH (C, D, E, c, e) and K-matched RBC units (RBCus) from a predominantly European donor population. Over the 11-year period in the Paris area, 6496 patients received transfusion at least once for a total of 239 944 units. Antibodies were made by 1742 patients. The first antibodies of a patient were predictive of subsequent immunization. By the 17th RBCu transfused (by the 20th, excluding warm autoantibodies), 75% of the patients who would make antibodies had made their first. By the 16th, 90% who would make antibodies to a high frequency antigen had made their first antibody to these antigens. Females made their first antibodies slightly earlier than males. Patients who received multiple transfusions (>50 units) had a higher immunization prevalence than those who rarely received transfusion (<12 units) but fewer clinically significant antibodies. Patients with SCD and prophylactic RH-K matching not immunized by the 20th RBCu are likely to have a low alloimmunization risk (to antigens other than RH-K), that is, be low responders, especially relative to the most clinically significant antibodies. This number of 20 units is a point before which close monitoring of patients is most important but remains open to future adjustment.

Revisiting the benefits of isovolemic hemodilution red cell exchange for sickle cell disease

BACKGROUND

Isovolemic hemodilution red cell exchange (IHD-RCE) is a modified form of the standard red cell exchange (STD-RCE), intended to reduce red cell requirements in patients with sickle cell disease (SCD). This retrospective crossover analysis of nine patients aims to add to the limited existing literature on IHD-RCE and address the equipoise regarding whether the benefits of (a) decreased RBC usage per exchange and (b) increased interprocedure interval (via lower fraction of cells remaining, FCR) can be observed at the same time, in the same patient.

METHODS

At a single center, we identified 37 patients with SCD undergoing chronic RCE between 2014 and 2021. We excluded those patients who did not have at least six consecutive procedures of each type (STD- and IHD-RCE), arriving at nine patients for analysis.

RESULTS

When using greater decreases in hematocrit than previously published, we did not find that IHD-RCE resulted in any clinically apparent adverse events. We did find greater decreases in diastolic blood pressure and increases in heart rate in some patients, as compared to STD-RCE. After correcting for total blood volume, seven of the nine patients had significantly reduced red cell requirements with each IHD-RCE. Because the pattern of achieving a lower FCR than programmed was seen to an equal extent with both IHD-RCE and STD-RCE, none of the nine patients showed any statistical difference in actual FCR between procedure types.

DISCUSSION

Our data do not support the observation of both IHD-RCE benefits, decreased red cell usage per exchange and lower FCR/increased interprocedure interval, simultaneously.

Comprehensive guide to managing a chronic automated red cell exchange program in sickle cell disease

Sickle cell disease (SCD) is associated with significant morbidity and mortality, and limits both the quality and quantity of life. Transfusion therapy, specifically automated red cell exchange (aRCE), plays a key role in management of SCD and is beneficial for certain indications in the chronic, outpatient setting. The approach to maintain a successful chronic aRCE program for SCD is multifaceted. This review will highlight important considerations including indications for aRCE, patient selection, transfusion medicine pearls, vascular access needs, complications of therapy, aRCE prescription, and therapy optimization. Moreover, the importance of a multidisciplinary approach with frequent communication between the services involved cannot be overstated. Ultimately, the underlying goal of a chronic RCE program is to improve the quality of life and longevity of patients with SCD.

Barriers and Facilitators to Chronic Red Cell Transfusion Therapy in Pediatric Sickle Cell Anemia

Background: Chronic red cell transfusion (CRCT) therapy is one of a few effective disease-modifying therapies for children with sickle cell anemia (SCA). CRCT is recommended for primary and secondary stroke prevention for at-risk children with SCA and is sometimes used for other disease-related complications. However, CRCT can be resource- and time-intensive for patients/families, providers, and organizations. This study was conducted to provide a comprehensive, multilevel examination of barriers and facilitators to transfusion therapy in children with SCA from health care provider and caregiver perspectives. Methods: A qualitative descriptive approach was used to conduct key informant interviews in a sample of 26 caregivers and 25 providers across the United States. Interviews were analyzed using directed content analysis with the Multilevel Ecological Model of Health as an initial coding framework and the constant comparison method. Results: Ten barrier themes and 10 facilitator themes emerged across all ecological levels. Themes most commonly occurred on the patient and organizational levels. Key barriers themes included Logistical Challenges, Obtaining and Maintaining Venous Access, Alloantibodies/Alloimmunization and Reactions, and Iron Overload and Adherence to Chelation Therapy. Key facilitator themes included Nursing and Non-nursing Staff Support, Positive Child/Family Experiences, Logistical Help and Social Resources, Blood Bank and Access to Blood, and Transfusion-Specific Resources. Discussion: The comprehensive understanding of multilevel barriers and facilitators to transfusion therapy, including the role of nursing, in children with SCA can inform strategies to improve CRCT for patients/families and providers and can also be applied by organizations seeking to implement transfusion services for SCA.

Apheresis practice patterns in the United States of America: Analysis of a market claims database

INTRODUCTION

Indications for apheresis procedures are expanding; however, the evidence for many is low quality. A better understanding of apheresis patterns in the United States is needed to better plan prospective research studies.

METHODS

Data from January 1, 2013, to September 30, 2015, were analyzed from the IBM MarketScan Research Databases of de-identified health insurance claims data of several million enrollees at all levels of care from large employers and health plans across the United States. Apheresis procedures were identified by International Classification of Diseases, Ninth version (ICD-9) and Current Procedure Terminology (CPT) codes.

RESULTS

Combining inpatients and outpatients, 18 706 patients underwent 70 247 procedures. The patients were 52.7% female, 5.1% <18 years, and 55.9% inpatient, while the procedures were 49.5% female, 5.7% <18 years, and 19.8% inpatient. For each apheresis modality, the percent of patients treated and procedures performed, respectively, are plasmapheresis 36.4% and 42.5%, autologous harvest of stem cells 22.8% and 10.7%, plateletpheresis 11.1% and 3.5%, allogeneic harvest of stem cells 8.2% and 2.5%, photopheresis 5.4% and 24.4%, erythrocytapheresis 3.8% and 4.7%, leukopheresis 2.0% and 0.7%, immunoadsorption 1.4% and 0.4%, extracorporeal selective adsorption/filtration and plasma reinfusion 1.0% and 3.6%, and other 21.6% and 6.9%. A wide variety of diagnoses were treated; however, analysis of the diagnoses suggests the procedure codes may not always reflect an apheresis procedure.

CONCLUSION

This study describes the landscape of apheresis in the United States, but may overestimate some procedures based on linked diagnosis codes. Direct measures of apheresis procedures are needed to plan future research studies.

Safety and benefits of automated red cell depletion-exchange compared to standard exchange in patients with sickle cell disease undergoing chronic transfusion

BACKGROUND

The Spectra Optia allows automated performance of red blood cell reduction and isovolemic hemodilution (IHD) prior to standard red cell exchange (RCE), and is primarily intended for patients with sickle cell disease (SCD) undergoing chronic RCE. Data on the safety of inducing transient further anemia and the benefits of IHD-RCE is limited and occasionally contradictory.

STUDY DESIGN AND METHODS

In this retrospective crossover analysis of six patients with SCD who underwent chronic exchange with standard RCE (Cobe Spectra) followed by IHD-RCE (Spectra Optia), we compared safety and benefit outcomes with IHD-RCE vs standard RCE.

RESULTS

There were statistically but not clinically significant drops in blood pressure in the post-IHD phase. With IHD-RCE, there were significant reductions in red blood cell (RBC) usage and/or lower fraction of cells and significant increases in postprocedure hematocrit (Hct) associated with increased preprocedure Hct. There were no differences achieved in the time interval between procedures or in the net RBC gain with IHD-RCE. Overall, there were also no significant differences in pre- and postprocedure percentage of hemoglobin S, reticulocyte count, interval daily hemoglobin A decrement, or postprocedure white blood cell, neutrophil, or platelet counts.

CONCLUSIONS

Our study supports that IHD-RCE can be safely used in patients with stroke risk and compared to standard RCE, results in benefits of lower RBC usage and/or fraction of cells remaining and higher postprocedure Hct associated with higher preprocedure Hct. These findings support wider use of IHD-RCE, especially in the current environment with reduced availability of minority units.