Antibodies to human leukocyte antigens and their association with blood product exposures in pediatric patients undergoing cardiac transplantation.

BACKGROUND AND AIMS: Previous blood product exposures may result in the development of antibodies to human leukocyte antigens (HLA). Pediatric heart transplant recipients who have these antibodies experience increased morbidity and mortality after transplantation. In this study, our aims were to confirm the association of previous allogeneic blood product exposures with the formation of anti-HLA antibodies, determine which blood components pose the greatest risk of developing antibodies, and assess differences in outcomes after transplantation between patients who had anti-HLA antibodies and those who did not. METHODS: This retrospective investigation included all children who underwent cardiac transplantation at Children's Healthcare of Atlanta from January 1, 2015 through December 31, 2018. Chart reviews were performed to collect pertinent data. Anti-HLA antibodies were detected by single antigen bead testing. Antibody burden was tabulated using the calculated panel reactive antibody (cPRA) score immediately prior to transplantation. Statistical analyses were conducted to examine differences based on HLA antibody status and identify associations with outcomes of interest. RESULTS: Our results show a significant association between pretransplant blood product exposures and HLA antibody status. Children with a pretransplant blood product exposure had 7.98 times the odds of developing an anti-HLA antibody compared to those without a pretransplant blood product exposure (p = .01). We also found a significant association between a previous red blood cell (RBC) exposure and HLA antibody status (p = .01) which was not found for other blood component exposures. Patients who were HLA antibody positive were more likely to develop a donor-specific antibody (DSA) after transplantation (p = .04). CONCLUSIONS: Exposure to previous allogeneic blood products affects the development of anti-HLA antibodies in children presenting for heart transplantation. Previous RBC exposures resulted in HLA antibody positivity more than other blood component exposures. Importantly, the presence of HLA antibodies was associated with the development of DSAs post-transplantation. Developing transfusion strategies to reduce allogeneic blood product exposures in children who may need future cardiac transplantation should be a high priority.

Daratumumab: Beyond Multiple Myeloma.

Daratumumab (DARA) is the biological name of an Immunoglobulin G1k human monoclonal antibody. DARA the first-in-class therapy targeting CD38 expressing- plasma cells (PC) and plasma blasts. It has been approved for the treatment of multiple myeloma. It is also being examined in the setting of other hematologic malignancies. As DARA targets PCs, it could potentially be used to treat many other disease processes that are antibody mediated. In fact, several case reports and case series report experiences of using DARA to treat a variety of antibody-mediated disorderss. The aim of this review is to present a summary of the literature thus far regarding the application of DARA beyond its uses in multiple myeloma and other hematologic diseases. Specifically, we address uses of DARA as an immunologic modulator in various antibody mediated processes.

Development of iron deficiency anemia in patients undergoing extracorporeal photopheresis: Comparison of the UVAR and CELLEX instruments.

INTRODUCTION: Extracorporeal photopheresis (ECP) is a procedure used to influence T-cell activity in patients suffering from immune-mediated cellular damage secondary to activated lymphocytes. Although well-tolerated, iron deficiency anemia (IDA) has been described. The goal herein is to describe IDA in patients who received extracorporeal photopheresis (ECP) treatment using UVAR (Therakos Inc) and CELLEX (Therakos Inc) instruments. DESIGN AND METHODS: Patients treated with ECP from 2015 to 2019 were retrospectively analyzed. IDA was defined by a decrease in hemoglobin following treatment with concomitant decrease in mean cell volume, mean corpuscular hemoglobin concentration, increased RBC distribution width, and/or iron studies compatible with IDA. RESULTS: During the four-year study period, thirty-four patients received ECP. Thirteen (38%) underwent treatment with the previous UVAR device while 21 (62%) received treatment on the newer CELLEX instrument. Nineteen (56%) of the cohort developed clinical and laboratory evidence of IDA with an average of 3.2 g/dL decrease in hemoglobin. Patients who developed IDA treated on the CELLEX instrument experienced a significantly greater drop in hemoglobin (P = .04) than those treated on the UVAR. Examining the CELLEX-treated patients, those who received the procedure at greater frequency experienced significantly greater drops in hemoglobin (P = .03). CONCLUSIONS: IDA is a risk of chronic ECP therapy and is likely secondary to retained blood components in the instrument. The temporal relationship between anemia and ECP treatment has a direct correlation with the treatment schedule. Patients undergoing ECP treatment should be closely monitored for the development of IDA.

The utility of second single antigen bead assay: Clearing the water or stirring up mud?

Though solid-phase single antigen bead (SAB) testing has provided major advances to the HLA community and organ allocation, it has not been without limitations. In particular, false-positive reactions lead to interpretative challenges and the potential to preclude a transplant if the corresponding antigens are deemed unacceptable. Two different vendor platforms are commercially available for SAB testing, one more recent than the other. The aim herein was to assess the benefit of using the newer SAB platform in situations where the primary platform yielded suspicious (specifically, false positive) reactions. Therefore, 42 serum samples with commonly encountered false-positive patterns observed in our laboratory were tested with the newer platform. Cases were classified as resolved, equivalent, or divergent based on whether the second platform produced no reactivity, the same pattern, or a distinctly different pattern compared to the primary platform, respectively. Approximately 33% of cases were resolved, 46% were equivalent, and 21% were divergent. The project revealed advantages of adding a second SAB platform to the laboratory's test menu including resolving challenging samples and including broader coverage of different alleles and unique class II alpha/beta subunit combinations. However, the challenges of validating, maintaining, and billing for another test method in the laboratory may be barriers to routine use.

Sensitization in transplantation: Assessment of risk (STAR) 2019 Working Group Meeting Report.

The purpose of the STAR 2019 Working Group was to build on findings from the initial STAR report to further clarify the expectations, limitations, perceptions, and utility of alloimmune assays that are currently in use or in development for risk assessment in the setting of organ transplantation. The goal was to determine the precision and clinical feasibility/utility of such assays in evaluating both memory and primary alloimmune risks. The process included a critical review of biologically driven, state-of-the-art, clinical diagnostics literature by experts in the field and an open public forum in a face-to-face meeting to promote broader engagement of the American Society of Transplantation and American Society of Histocompatibility and Immunogenetics membership. This report summarizes the literature review and the workshop discussions. Specifically, it highlights (1) available assays to evaluate the attributes of HLA antibodies and their utility both as clinical diagnostics and as research tools to evaluate the effector mechanisms driving rejection; (2) potential assays to assess the presence of alloimmune T and B cell memory; and (3) progress in the development of HLA molecular mismatch computational scores as a potential prognostic biomarker for primary alloimmunity and its application in research trial design.

Electronic charting of transfusion medicine consults: implementation, challenges and opportunities.

BACKGROUND: The Joint Commission lists improving staff communication (handoffs) as part of several National Safety Goals. In this study, we developed an electronic web-based charting system for clinical pathology handoffs, which primarily consist of transfusion medicine calls, and evaluated the advantages over a paper-based handwritten call log. MATERIALS AND METHODS: A secure online web browser application using Research Electronic Data Capture (REDCap) was designed to document on-call pathology resident consults. A year after implementation, an online survey was administered to our pathology residents in order to evaluate and compare the usability of the electronic application (e-consults) to the previous handwritten call log, which was a notebook where trainees hand wrote different components of the consult. RESULTS: The REDCap web-based application includes discrete fields for patients' information, requesting physician contact, type of consult, action items for follow-up and faculty responses, as well as other information. These components have eventually progressed to be an online consult call catalog. With approximately 1079 consults per year, transfusion medicine-related calls account for ~90% of the encounters, while clinical chemistry, microbiology and immunology calls constitute the remainder. The overall response rate of the survey was 96% (29 of 30 participants). Of the 16 respondents who experienced both call log systems, 100% responded that REDCap was an improvement over the handwritten call log (P < 0·0001). CONCLUSION: E-consult documentation entered into a web-based application was a user-friendly, secure clinical information access and effective handoff system as compared to a paper-based handwritten call log.

Identification of a recurrent pattern of false-positivity by Luminex HLA MHC class I single antigen bead testing.

Previously, a distinct MHC class II Luminex-single antigen bead (SAB) pattern was described and attributed to antibodies targeting denatured antigens. In this study, we describe a distinct MHC class I reactivity pattern observed in 1.8% (105/5992) of samples resulted in 2017. The pattern displays reactivity to the following Luminex-SABs: HLA-A*33:03, A*36:01, A*80:01, B*54:01, B*53:01, C*06:02, C*07:02, C*18:02, C*14:02, C*03:03, C*03:04, and C*15:02. This pattern was identified in patients with no sensitization history, negative FlowPRA results, and antibody to self-antigen(s). Epitope analysis failed to reveal a common determinant(s) to explain this pattern of reactivity. Additionally, we found this pattern to be prevalent in female patients (62%) and also those with systemic lupus erythematosus (62%). Given these findings, we speculate this pattern likely represents false-positive reactivity, possibly due to antibody targeting denatured antigens or a specific peptide, molecular mimicry, autoimmunity, or a combination thereof.

The impact of belatacept on third-party HLA alloantibodies in highly sensitized kidney transplant recipients.

Recent evidence suggests that belatacept reduces the durability of preexisting antibodies to class I and class II human leukocyte antigens (HLAs). In this case series of 163 highly sensitized kidney transplant candidates whose calculated panel-reactive antibody (cPRA) activity was ≥98% to 100%, the impact of belatacept on preexisting HLA antibodies was assessed. Of the 163 candidates, 72 underwent transplantation between December 4, 2014 and April 15, 2017; 60 of these transplanted patients remained on belatacept consecutively for at least 6 months. We observed a decrease in the breadth and/or strength of HLA class I antibodies as assessed by FlowPRA in belatacept-treated patients compared to controls who did not receive belatacept. Specifically, significant HLA antibody reduction was evident for class I (P < .0009). Posttransplant belatacept-treated patients also had a clinically significant reduction in their cPRA compared to controls (P < .01). Collectively, these findings suggest belatacept can reduce HLA class I antibodies in a significant proportion of highly sensitized recipients and could be an option to improve pretransplant compatibility with organ donors.

How do I implement diagnostic management teams in transfusion medicine?

Diagnostic management teams (DMTs) were conceptualized approximately twenty years ago in response to increasing subspecialization in medicine. DMTs are a collaboration between diagnostic experts and clinicians that aim to improve accurate and timely diagnosis and treatment of disease. Diagnostic experts provide their expertise in the increasingly complex realm of laboratory testing and interpretation of those test results to guide appropriate test utilization for individual patients. Not only can this approach improve patient care and safety, but DMTs also decrease healthcare costs by reducing unnecessary testing and potential diagnostic errors. Following the DMT construct and principles along with the 2015 National Academy of Medicine recommendations, our transfusion medicine (TM) service streamlined the workup and management of platelet refractory (PR) patients by developing and implementing a formal PR laboratory consult. The goals of this DMT and consult are to improve diagnostic management of PR patients and to decrease delays in providing these patients with appropriate and compatible platelet units. A comprehensive interpretation of test results is directly uploaded to the patient's electronic medical record (EMR), which is associated with a CPT code allowing for compensation for the PR evaluation. Herein we describe the development of and experience with the DMT since its implementation.

The impact of transfused blood products on deceased donor HLA typing.

Accurate deceased donor HLA typing assumes that the blood sample tested contains only DNA from the organ donor. Prior to procurement, many organ donors are transfused at least one unit of red blood cells (RBC). Non-organ donor DNA acquired from transfusions may result in incorrect and/or ambiguous HLA typing. To address this question, we investigated the impact of RBC transfusion on organ donor HLA typing by using different in vitro transfusion models: leukoreduced (LR) and non-LR RBCs. Various quantities of LR and non-LR RBCs were added to normal peripheral blood and HLA typing was performed by real time PCR. Our results show that HLA typing of deceased donors can be impacted dependent upon the type and quantity of transfused RBCs. Importantly, if LR RBCs are given, HLA typing is unlikely to be affected, precluding the need to delay typing and obtain an alternative source of donor DNA.

Daratumumab in multiple myeloma.

The development of effective monoclonal antibodies for the treatment of myeloma has been a long journey of clinical and drug development. Identification of the right target antigen was a critical part of the process. CD38 as a target has been considered for some time, but clinically, daratumumab, a CD38 monoclonal antibody, was the first to be tested, and it has delivered the best clinical responses as a single agent to date. Its proven safety and efficacy in combination with other antimyeloma agents have led to several US Food and Drug Administration approvals for treating myeloma. Furthermore, the results of early trials in the induction therapy setting have demonstrated a beneficial role when it is added to the existing induction regimens. This review summarizes the importance of CD38 as a target and examines the clinical development of the CD38 monoclonal antibody daratumumab and its clinical significance in combination regimens in both patients with relapsed/refractory myeloma and patients with newly diagnosed myeloma.

Development, Implementation, and Evaluation of a Fourth-Year Medical School Elective Course in Blood Banking and Transfusion Medicine.

Objectives: Knowledge of transfusion medicine by medical students is limited. Transfusion medicine physicians developed, implemented, and evaluated a half-day elective on transfusion medicine for fourth-year medical students. Methods: The course included a didactic lecture with integrated audience response questions and role-playing, as well as a "Jeopardy"-style game to review the material. The same 10-question knowledge quiz was administered before and after the elective. Results: Both knowledge quizzes were taken by 102 students. An average score of 3.3 was obtained on the initial quiz, with only three (3%) students having a passing score (≥6 correct questions). The average score after the elective was 6.6, with 83 (81%) students having a passing score. Students found the elective was informative (62 students, 60.8%), very useful (56, 54.9%), and practical (51, 50%), although some thought it was challenging (22, 21.6%). Conclusions: A short course for medical students that allowed repetition of concepts using several teaching modalities improved their knowledge in transfusion medicine.

Stability of anti-A blood group titers among blood group B renal transplant candidates.

BACKGROUND: As deceased donor kidney allocation is based in part on blood type compatibility, group B candidates are disadvantaged due to their disproportionate representation on the wait list compared to the group B donor pool. To mitigate this discrepancy, group B candidates can receive group A2 or A2 B donor kidneys if their anti-A titers are below a predetermined cutoff. Currently, eligibility is reverified quarterly to UNet based on individual center protocols, which can vary due to a lack of set guidelines for monitoring ABO titers in these patients. Our goal was to assess the stability of anti-A titers in blood group B renal transplant candidates over time to provide data that could aid in the development of standardized ABO titer protocols. STUDY DESIGN AND METHODS: Titers performed between January 2011 and December 2015 were assessed for 191 group B patients with two or more documented titers. RESULTS: Fifty patients (26%) were ineligible, as the first titer exceeded the cutoff of 8. Of the remaining 141 patients, 19 (13%) became ineligible as the second titer exceeded 8. Thirty-nine patients (28%) had no change in titer between samples, while 71 (50%) had a titer change that never exceeded 8. Only 12 patients (8.5% of total) experienced a titer change that affected eligibility after the second test. CONCLUSION: Although patients experience some variability in anti-A titers over time, in most cases, stability did not affect candidate eligibility. Our results indicate that regular testing beyond the second titer may be unnecessary and represent test overutilization.

Current state of transfusion practices for ABO-incompatible pediatric heart transplant patients in the United States and Canada.

BACKGROUND: ABO compatibility restriction on solid organ transplantation limits organ availability. In an effort to increase organ availability, pediatric ABO-incompatible heart transplants (ABOiHT) are now performed with similar outcomes to ABO-compatible transplants. Transfusion support can be challenging and currently there are no standard guidelines for blood product support, ABO isohemagglutinin (IH) titer cutoffs for transplant eligibility, or therapeutic intervention for these patients. The study aim was to survey current blood bank and antibody reduction practices for pediatric ABOiHT in the United States and Canada. STUDY DESIGN AND METHODS: A Web-based survey was sent to 50 US and Canadian pediatric blood bank directors. Participants were queried regarding pre-, intra-, and postoperative blood product support; ABO IH titer testing; and antibody reduction practices in ABOiHT recipients. RESULTS: We analyzed 21 responses from US and Canadian centers that perform pediatric ABOiHT. There is wide variation in the type of blood products transfused and the modification of these products among respondents in the pre-, intra-, and postoperative settings. The frequency of testing ABO IH titers, implementing therapeutic intervention, and the type of therapeutic intervention also vary greatly among the institutions. CONCLUSION: Transfusion support of children with ABOiHT varies widely among blood banks in the United States and Canada. The choice of blood products and modifications utilized, titer thresholds for organ selection and medical decision points, and antibody reduction strategies are not standardized from center to center. As pediatric ABOiHTs become more common, a better understanding of optimal transfusion support and therapeutic intervention is needed.

(F)Utility of the physical crossmatch for living donor evaluations in the age of the virtual crossmatch.

Flow cytometric crossmatches (FCXM) are routinely performed to support living-donor renal transplantation. While long a laboratory mainstay, a physical crossmatch is costly, time consuming, and frequently poses interpretative conundrums with both false-positive and false- negative results. Given the increased utilization of the virtual crossmatch (vXM) in the deceased donor setting, our aim was to assess its utility in living donor evaluations. We reviewed 100 living donor FCXMs and retrospectively performed a vXM for each pair. Seventy-five (75) cases were concordant, (i.e., FCXM-/vXM- or FCXM+/vXM+) while 25 cases were discordant; Five were vXM+/FCXM- and 20 were FCXM+/vXM-. Since donor-specific antibodies (DSA) were not detected in the 20 FCXM+/vXM- cases, these were interpreted as false-positive, i.e., due to non-HLA antibodies. Importantly, none of these patients, when transplanted across a positive FCXM, experienced early antibody mediated rejection or subsequently developed HLA DSA. These data reveal that, for the vast majority of living donor evaluations, a vXM is an acceptable vetting procedure.

Understanding solid-phase HLA antibody assays and the value of MFI.

As the practice of medicine becomes more reliant on imaging and laboratory tests, medical decisions will be increasingly based on numbers. Accordingly, following the introduction of solid-phase testing to the HLA testing repertoire, laboratory directors and physicians have employed preset mean fluorescence intensity (MFI) thresholds as the basis for decisions in the management of transplant patients. However, what do MFI values mean? The literature is rife with reports detailing numerous factors that influence antibody assessment including (but not limited to) sensitization history of the patient, level of mismatch between donor and recipient, presence of interfering substances in the serum, whether the antigen on multiplex beads is native or denatured, day-to-day and technologist variability, and the historical performance of an assay in a given institution. How are these variables incorporated into the interpretation of MFI values? Herein, the pitfalls and complexities of single antigen bead (SAB) testing and interpretation are discussed with specific attention to what can and cannot be inferred by MFI.