Efficacy of a Dual-Epitope Dendritic Cell Vaccine as Part of Combined Immunotherapy for HER2-Expressing Breast Tumors.

Previous work from our group and others has shown that patients with breast cancer can generate a T cell response against specific human epidermal growth factor 2 (HER2) epitopes. In addition, preclinical work has shown that this T cell response can be augmented by Ag-directed mAb therapy. This study evaluated the activity and safety of a combination of dendritic cell (DC) vaccination given with mAb and cytotoxic therapy. We performed a phase I/II study using autologous DCs pulsed with two different HER2 peptides given with trastuzumab and vinorelbine to a study cohort of patients with HER2-overexpressing and a second with HER2 nonoverexpressing metastatic breast cancer. Seventeen patients with HER2-overexpressing and seven with nonoverexpressing disease were treated. Treatment was well tolerated, with one patient removed from therapy because of toxicity and no deaths. Forty-six percent of patients had stable disease after therapy, with 4% achieving a partial response and no complete responses. Immune responses were generated in the majority of patients but did not correlate with clinical response. However, in one patient, who has survived >14 y since treatment in the trial, a robust immune response was demonstrated, with 25% of her T cells specific to one of the peptides in the vaccine at the peak of her response. These data suggest that autologous DC vaccination when given with anti-HER2-directed mAb therapy and vinorelbine is safe and can induce immune responses, including significant T cell clonal expansion, in a subset of patients.

Race, rituximab, and relapse in TTP.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is characterized by recurring episodes of thrombotic microangiopathy, causing ischemic organ impairment. Black patients are overrepresented in iTTP cohorts in the United States, but racial disparities in iTTP outcome and response to therapy have not been studied. Using the United States Thrombotic Microangiopathies Consortium iTTP Registry, we evaluated the impact of race on mortality and relapse-free survival (RFS) in confirmed iTTP in the United States from 1995 to 2020. We separately examined the impact of rituximab therapy and presentation with newly diagnosed (de novo) or relapsed iTTP on RFS by race. A total of 645 participants with 1308 iTTP episodes were available for analysis. Acute iTTP mortality did not differ by race. When all episodes of iTTP were included, Black race was associated with shorter RFS (hazard ratio [HR], 1.60; 95% CI, 1.16-2.21); the addition of rituximab to corticosteroids improved RFS in White (HR, 0.37; 95% CI, 0.18-0.73) but not Black patients (HR, 0.96; 95% CI, 0.71-1.31). In de novo iTTP, rituximab delayed relapse, but Black patients had shorter RFS than White patients, regardless of treatment. In relapsed iTTP, rituximab significantly improved RFS in White but not Black patients. Race affects overall relapse risk and response to rituximab in iTTP. Black patients may require closer monitoring, earlier retreatment, and alternative immunosuppression after rituximab treatment. How race, racism, and social determinants of health contribute to the disparity in relapse risk in iTTP deserves further study.

How do I reduce variation in red blood cell transfusion practices in a large integrated health care system?

BACKGROUND: Reducing variation in transfusion practices can prevent unwarranted transfusions, an outcome that improves quality of care and patient safety, while lowering costs and eliminating waste of blood. We developed and assessed a system-wide initiative to reduce variation in red blood cell (RBC) transfusion in terms of both transfusion utilization and the number of units transfused. INTERVENTION DESIGN AND METHODS: Our initiative combined a single-unit default order for RBC transfusion in hemodynamically stable, non-bleeding patients with a "Why Give 2 When 1 Will Do?" Choosing Wisely campaign, while also promoting a restrictive hemoglobin threshold (Hb <7 g/dl). This multimodal intervention was implemented across an academic medical center (AMC) with over 950 beds and 10 community hospitals. RESULTS: Between our baseline (CY 2020) and intervention period (CY 2021), single-unit orders increased from 57% to 70% of all RBC transfusion orders (p < .001). The greatest change in ordering practices was at community hospitals, where single-unit orders increased from 46% to 65% (p < .001). Over the same time period, the system-wide mean (SD) Hb result prior to transfusion fell from 7.3 (0.05) to 7.2 g/dl (0.04) (p < .05). We estimate this effort saved over 4000 units of blood and over $4 million in direct and indirect costs in its first year. DISCUSSION: By combining a single-unit default setting in the RBC order with a restrictive hemoglobin threshold, we significantly reduced variation in ordering practices. This effort demonstrates the value of single-unit policies and "nudges" in system-wide patient blood management initiatives.

Considerations for immune effector cell therapy collections: a white paper from the American Society for Apheresis.

BACKGROUND AIMS: This white paper was developed to provide leukapheresis guidance for the collection of mononuclear cells from adult and pediatric patients who are destined for immune effector cell (IEC) therapies for commercial and research applications. Currently, there is considerable variability in leukapheresis processes and limited published information regarding best practices relevant to new cellular therapies, especially IECs. Herein the authors address critical leukapheresis questions in five domains to help guide consistent collection processes and ensure high-quality products. The first four domains are onboarding, pre-collection, collection and post-collection, with protocol feasibility, preparation, care and follow-up of the patient/donor at each step, respectively, and technical considerations during collection. The fifth domain of quality assurance focuses on ensuring product potency, purity, safety and auditing. METHODS: The American Society for Apheresis (ASFA) Clinical Applications Committee (IEC Therapy Subcommittee) was charged by the society's board of directors with working collaboratively with other ASFA committees and organizations, including the Foundation for the Accreditation of Cellular Therapy, Association for the Advancement of Blood and Biotherapies, American Society for Transplantation and Cellular Therapy, National Marrow Donor Program and International Society for Cell & Gene Therapy, to develop guidelines regarding leukapheresis collection of cells destined for the manufacture of IEC therapies. After a review of the literature and discussion with members of the involved committees and various institutions, a draft guidance was created and circulated for comment and revision. RESULTS: Critical aspects of apheresis that could affect the quality and quantity of the leukapheresis product were identified. These areas were then discussed and reviewed. After consensus, the best practice guidelines were proposed and accepted. CONCLUSIONS: In the current era of rapid growth of IEC therapies, it is important to address critical leukapheresis steps to provide high-quality products and more consistent practices and to eliminate redundant efforts.

Blood conservation strategies at United States hospitals during the COVID-19 pandemic: Findings from a multi-institutional analysis - International Society of Blood Transfusion survey.

BACKGROUND: Due to the coronavirus disease 2019 (COVID-19) pandemic, the transfusion medicine community has experienced unprecedented blood supply shortages since March 2020. As such, numerous changes to everyday practice have occurred with a specific emphasis on blood conservation. We sought to determine the strategies used to mitigate blood shortages and promote blood conservation during the pandemic. METHODS: An anonymous, 37-question survey was developed using Research Electronic Data Capture and distributed via e-mail to transfusion medicine specialists across the US obtained via publicly available databases. RESULTS: Amongst surveyed [41.1% response rate (51/124 institutions)], 98.0% experienced a product shortage, with the greatest number reporting red blood cell (RBC) shortages (92.0%). This led to 35.3% of institutions altering the composition and/or number of blood product suppliers, including a 100% increase in the number of institutions acquiring blood from organizations that connect hospital transfusion services with blood collection centers (e.g., Blood Buy) compared to before March 2020. Prospective triaging of blood products was the most common blood conservation strategy (68.1%), though 35.4% altered their RBC exchange or transfusion program for patients receiving chronic RBC transfusion/exchange. As a result of these changes, 78.6% of institutions reported that these changes resulted in a reduction in blood product usage, and 38.1% reported a decrease in product wastage. CONCLUSIONS: Most hospitals experienced the effects of the supply shortage, and many of them implemented blood conserving measures. Conservation strategies were associated with decreased blood utilization and waste, and future studies could evaluate whether these changes persist.

Lack of defined apheresis collection criteria in publicly available CAR-T cell clinical trial descriptions: Comprehensive review of over 600 studies.

BACKGROUND: Chimeric antigen receptor T (CAR-T) cell successes have encouraged continued clinical study. Apheresis collection of starting material for CAR-T cell therapy product manufacturing is critical but described approaches suggest variability and clinical guidelines are currently lacking. The goal of this study was to gather and assess variability in apheresis collection descriptions in publicly available CAR T-cell therapy clinical trials. STUDY DESIGN: We searched clinicaltrials.gov (a publicly available clinical trial database) for "chimeric antigen receptor T cells" on July 01, 2020 and studies accessed July 30, 2020-August 15, 2020. Data collected included date posted, study characteristics, apheresis mentions (number, location, and context), laboratory parameters and transfusion allowances. Apheresis context was analyzed using a qualitative inductive approach of grounded theory method with open coding. Text was classified into 37 context codes, grouped into 12 categories, and then consolidated into patient, procedure, product, and miscellaneous themes. RESULTS: Apheresis was mentioned 1044 times in 322 (51.9%) of 621 total studies. Laboratory parameters mentioned included white blood cells (100 studies), absolute neutrophil count (220 studies), absolute lymphocyte count (102 studies), CD3+ cell (38 studies), hemoglobin (233 studies, 54 studies specified transfusion allowance), and platelet (269 studies, 48 studies specified transfusion allowance). CONCLUSIONS: Apheresis collection of CAR-T cell products is not well-defined in clinical study descriptions and the context is inconsistent. Laboratory parameters useful for apheresis collection are variably present and do not consistently align with current practices. Further exploration, and clinical guideline development will encourage alignment of apheresis collections for CAR-T cell products.

Red blood cells modulate structure and dynamics of venous clot formation in sickle cell disease.

Sickle cell disease (SCD) is associated with chronic activation of coagulation and an increased risk of venous thromboembolism. Erythrocyte sickling, the primary pathologic event in SCD, results in dramatic morphological changes in red blood cells (RBCs) because of polymerization of the abnormal hemoglobin. We used a mouse model of SCD and blood samples from sickle patients to determine if these changes affect the structure, properties, and dynamics of sickle clot formation. Sickling of RBCs and a significant increase in fibrin deposition were observed in venous thrombi formed in sickle mice. During ex vivo clot contraction, the number of RBCs extruded from sickle whole blood clots was significantly reduced compared with the number released from sickle cell trait and nonsickle clots in both mice and humans. Entrapment of sickled RBCs was largely factor XIIIa-independent and entirely mediated by the platelet-free cellular fraction of sickle blood. Inhibition of phosphatidylserine, but not administration of antisickling compounds, increased the number of RBCs released from sickle clots. Interestingly, whole blood, but not plasma clots from SCD patients, was more resistant to fibrinolysis, indicating that the cellular fraction of blood mediates resistance to tissue plasminogen activator. Sickle trait whole blood clots demonstrated an intermediate phenotype in response to tissue plasminogen activator. RBC exchange in SCD patients had a long-lasting effect on normalizing whole blood clot contraction. Furthermore, RBC exchange transiently reversed resistance of whole blood sickle clots to fibrinolysis, in part by decreasing platelet-derived PAI-1. These properties of sickle clots may explain the increased risk of venous thromboembolism observed in SCD.

Mathematical modeling of the impact of recirculation on exchange kinetics in tandem extracorporeal membrane oxygenation and therapeutic plasma exchange.

Vascular access connection configurations during tandem extracorporeal membrane oxygenation (ECMO) and therapeutic plasma exchange (TPE) may impact exchange kinetics. In these tandem procedures, typically the TPE inlet line is proximal to the TPE return line with respect to blood flow in the ECMO device, maximizing the opportunity for replacement fluid homogenization within the ECMO circuit. However, if TPE inlet and return line connections are switched, recirculation-a phenomenon in which replacement fluid leaving the TPE return line is prematurely drawn into the TPE inlet line prior to satisfactory homogenization within the ECMO circuit-will occur. Such recirculation could diminish TPE efficacy in patients on ECMO and mitigate therapeutic benefits. Using a mathematical model of recirculation in tandem ECMO and TPE, we demonstrate that the predicted impact of recirculation is negligible and vascular access connection positioning does not appear to be a point of clinical concern with regard to TPE kinetics.

Therapeutic plasma exchange taper does not decrease exacerbations in immune thrombotic thrombocytopenic purpura patients.

BACKGROUND: Despite rapid and intensive treatments with therapeutic plasma exchange (TPE) and immunosuppression, immune thrombotic thrombocytopenic purpura (TTP) patients are at risk of disease exacerbation, i.e., early recurrence of TTP within 30 days of achieving treatment response. TPE taper, a practice of performing additional TPE procedures after achieving treatment response, is commonly performed for decreasing exacerbations, although no evidence supports this practice. STUDY DESIGN AND METHODS: In this prospective observational investigation over four years, our center switched its standard of care for treating all TTP patients from not performing TPE taper after achieving treatment response (i.e., no-taper cohort) to performance of TPE taper (i.e., yes-taper cohort) to characterize impacts on exacerbations. Continuous and categorical data were analyzed by Mann-Whitney, Fisher's exact, and log-rank tests; significance was defined as p < 0.05. RESULTS: The two cohorts were well matched and had no significant differences in demographics, presentation laboratory values, or TTP history (p > 0.05 for all). The yes-taper cohort of 26 patients with 29 consecutive episodes did not have a significantly different exacerbation rate from the no-taper cohort of 24 patients with 27 consecutive episodes (exacerbation rates of 37.9% vs. 33.3%, respectively; p = 0.78); however, treatment-related complications directly attributed to the TPE procedures, blood products, or central venous catheters were significantly greater in the yes-taper cohort (nine vs. one events, respectively; p = 0.01). CONCLUSION: Since TPE taper did not reduce exacerbations in our TTP patients, we no longer advocate for TPE taper and have reverted to our original standard of care.

Heparin-induced thrombocytopenia associated with collection of hematopoietic progenitor cells by apheresis.

Heparin-induced thrombocytopenia (HIT) can occur following exposure to heparin and is characterized by thrombocytopenia with increased risk for thrombosis. This condition is mediated by formation of immunoglobulin G antibodies against platelet factor 4/heparin complexes that can subsequently lead to platelet activation. Herein, we detail the clinical and laboratory findings, treatments, and outcomes of two patients who developed HIT and thrombosis after undergoing collection of hematopoietic progenitor cells by apheresis (HPC-A) for autologous HPC transplant. Given that heparin may be used during HPC-A collections, these cases emphasize the importance of prompt consideration of HIT in patients that develop thrombocytopenia and thrombosis following HPC-A collection with heparin anticoagulation.

Evaluation of mobilization efficacy with an extended interval following plerixafor administration.

Plerixafor is a hematopoietic stem cell mobilizing agent used in combination with granulocyte-colony stimulating factor to improve collection for autologous stem cell transplantation. Despite a recommendation for administration 11 h prior to apheresis per package labeling, logistical challenges lead many institutions to administer plerixafor at an extended interval. The purpose of this study was to determine if plerixafor effectively and efficiently mobilizes CD34+ cells when given at an extended interval prior to apheresis. This was a retrospective evaluation of adult patients who received plerixafor based on an algorithm reserving daily plerixafor only for patients with a pre-apheresis CD34+ count of < 20 cells/µL (pre-apheresis plerixafor) or with a low CD34+ yield after the first apheresis session (rescue plerixafor). The primary outcome was achievement of a disease-specific collection goal of ≥ 6 ×106 CD34+ cells/kg for multiple myeloma and ≥ 4 ×106 CD34+ cells/kg for lymphoma. The mean interval between plerixafor administration and apheresis was 17 h in this study. Despite this extended interval, 64% of patients met their disease-specific collection goal. A minimum collection goal of ≥ 2 ×106 CD34+ cells/kg was achieved by 95% of patients. Mobilization remained efficient with a median of two days to complete collection. Based on this data, plerixafor effectively and efficiently mobilizes CD34+ cells when given at an extended interval prior to apheresis.

Effects of red-cell storage duration on patients undergoing cardiac surgery.

BACKGROUND: Some observational studies have reported that transfusion of red-cell units that have been stored for more than 2 to 3 weeks is associated with serious, even fatal, adverse events. Patients undergoing cardiac surgery may be especially vulnerable to the adverse effects of transfusion. METHODS: We conducted a randomized trial at multiple sites from 2010 to 2014. Participants 12 years of age or older who were undergoing complex cardiac surgery and were likely to undergo transfusion of red cells were randomly assigned to receive leukocyte-reduced red cells stored for 10 days or less (shorter-term storage group) or for 21 days or more (longer-term storage group) for all intraoperative and postoperative transfusions. The primary outcome was the change in Multiple Organ Dysfunction Score (MODS; range, 0 to 24, with higher scores indicating more severe organ dysfunction) from the preoperative score to the highest composite score through day 7 or the time of death or discharge. RESULTS: The median storage time of red-cell units provided to the 1098 participants who received red-cell transfusion was 7 days in the shorter-term storage group and 28 days in the longer-term storage group. The mean change in MODS was an increase of 8.5 and 8.7 points, respectively (95% confidence interval for the difference, -0.6 to 0.3; P=0.44). The 7-day mortality was 2.8% in the shorter-term storage group and 2.0% in the longer-term storage group (P=0.43); 28-day mortality was 4.4% and 5.3%, respectively (P=0.57). Adverse events did not differ significantly between groups except that hyperbilirubinemia was more common in the longer-term storage group. CONCLUSIONS: The duration of red-cell storage was not associated with significant differences in the change in MODS. We did not find that the transfusion of red cells stored for 10 days or less was superior to the transfusion of red cells stored for 21 days or more among patients 12 years of age or older who were undergoing complex cardiac surgery. (Funded by the National Heart, Lung, and Blood Institute; RECESS ClinicalTrials.gov number, NCT00991341.).

Bortezomib for Refractory Immune-Mediated Thrombocytopenia Purpura.

The treatment of refractory immune-mediated thrombocytopenia purpura (ITP) can be challenging. This case report describes treatment of refractory ITP with bortezomib, a proteasome inhibitor. This strategy has been successful in relapsing thrombotic thrombocytopenic purpura but is a novel therapeutic approach for ITP. Further research use of proteasome inhibition in refractory ITP may be warranted.

Treatment of acquired Thrombotic Thrombocytopenic Purpura in the U.S. remains heterogeneous: Current and future points of clinical equipoise.

BACKGROUND: The purpose of this survey was to describe current practices in the U.S. for treatment of acquired Thrombotic Thrombocytopenic Purpura (TTP), compare these with prior U.S. and current Canadian practices, and identify areas of clinical equipoise. STUDY DESIGN AND METHODS: A research team member administered the survey by telephone. Questions included an estimate of the annual patient volume treated, apheresis and medical therapy practices for acquired TTP. RESULTS: 32 centers from 22 states were surveyed. ADAMTS13 activity is used for confirmation of the diagnosis of acquired TTP (97%). Most commonly, daily plasma exchange (therapeutic plasma exchange [TPE]) is initiated with plasma as replacement fluid (91%) at 1.0 Plasma Volume (72%) and stopped with a platelet count of 150 × 109 /L (66%), and then TPE is tapered off (69%). Compared with a U.S. survey from 1998, a greater proportion of centers use plasma exclusively as the replacement fluid exclusively (29/32 vs 2/14 in 1998; P < .0001) and taper TPE (22/32 vs 8/20 in 1998, P = .0499). Compared with Canadian survey in 2016, a greater proportion of U.S. centers use plasma over cryosupernatant (29/32 vs 2/13 CAG centers, P < .0001) and initiate TPE with 1.0 PV compared with 1.5 PV (23/32 vs 0/14 CAG centers, P < .0001). Corticosteroid use is common but not universal (U.S. and CAG) and use of rituximab heterogeneous. CONCLUSION: Treatment of acquired TTP in the U.S. remains heterogeneous. Points of clinical equipoise identified were PV exchanged (1.0 vs >1.0), tapering of TPE versus none, and rituximab use.

Apheresis education in pathology residency.

INTRODUCTION: Physicians from diverse training backgrounds practice apheresis medicine. Pathology residents' exposure to apheresis may vary depending on which department performs these procedures. Milestones for Apheresis education were published in 2012, but the degree of utilization in residency curriculum development is unknown. This study describes the current state of apheresis education for pathology residents. METHODS: We sent a 15 question electronic survey to 141 pathology programs identified through the American Medical Association Residency and Fellowship Database. RESULTS: Forty-three (30.5%) of the 141 programs responded. Pathology performed apheresis procedures in 29 (67.4%) programs. In the remaining 14 programs, apheresis was performed by nephrology (10), hematology (4), and a regional blood center (1); in one program, both nephrology and hematology performed apheresis procedures. For combined anatomic and clinical pathology (AP/CP) residents, 26 of 28 (93%) were required to train in apheresis medicine when pathology performed the procedures compared to only 5 of 14 (36%) when they were performed by another department (P = 0.0002). For CP-only residents, 18 of 19 (95%) were required to train in apheresis medicine when pathology performed the procedures compared to 5 of 7 (71%) when they were performed by another department (P = 0.1669). Thirty (68.9%) respondents had a written apheresis medicine curriculum. Seventeen (39.5%) of the 43 respondents were aware of the Milestones for Apheresis education, and 8 (18.6%) used the milestones in creating their apheresis curriculum. CONCLUSIONS: The pathology department performed apheresis procedures in two-thirds of pathology residency programs surveyed. AP/CP residents were more likely to be required to train in apheresis medicine if the pathology department performed these procedures at their institution. Apheresis medicine practitioners should review the Milestones for Apheresis education with their residency program director to optimize learning and clinical skills development.

Venous access for hematopoietic progenitor cell collection: An international survey by the ASFA HPC donor subcommittee.

PURPOSE: Hematopoietic Progenitor Cell (HPC) collection by apheresis is performed in patients and donors to obtain HPCs for transplantation. Although studies have shown these procedures to be safe, successful collection cannot be performed without establishment of venous access. This project's objective was to ascertain the current practices of donor vein assessment and central venous catheter (CVC) usage. METHODS: The American Society for Apheresis (ASFA) HPC subcommittee created an electronic survey about precollection vein assessment and line placement, care, and removal in autologous and allogeneic donors. It was distributed to >5,000 possible participants, with one response analyzed per institution. RESULTS: One hundred centers performing autologous and/or allogeneic procedures provided adequate responses for analysis. Donor vein assessment is most often performed by apheresis staff more than 1 week prior to collection. For patients with questionable access, the next step performed most often is secondary assessment for autologous procedures and CVC placement for allogeneic procedures. Most centers use interventional radiology to place CVCs in jugular veins on collection day with placement verification through electronic medical records. Verbal and written postinsertion CVC care instructions are routinely provided. The apheresis team frequently provides postinsertion CVC care for autologous patients. Heparin is used most often for CVC lock. When used, tissue plasminogen activator is usually instilled for up to 60 min. CONCLUSION: These data summarize the largest single survey of donor vein assessment at institutions performing HPC collections by apheresis. The variations identified in donor venous access practice warrant further investigation and consensus to establish best practices. J. Clin. Apheresis 31:529-534, 2016. © 2015 Wiley Periodicals, Inc.

Alloimmunization is associated with older age of transfused red blood cells in sickle cell disease.

Red blood cell (RBC) alloimmunization is a significant clinical complication of sickle cell disease (SCD). It can lead to difficulty with cross-matching for future transfusions and may sometimes trigger life-threatening delayed hemolytic transfusion reactions. We conducted a retrospective study to explore the association of clinical complications and age of RBC with alloimmunization in patients with SCD followed at a single institution from 2005 to 2012. One hundred and sixty six patients with a total of 488 RBC transfusions were evaluated. Nineteen patients (11%) developed new alloantibodies following blood transfusions during the period of review. The median age of RBC units was 20 days (interquartile range: 14-27 days). RBC antibody formation was significantly associated with the age of RBC units (P = 0.002), with a hazard ratio of 3.5 (95% CI: 1.71-7.11) for a RBC unit that was 7 days old and 9.8 (95% CI: 2.66-35.97) for a unit that was 35 days old, 28 days after the blood transfusion. No association was observed between RBC alloimmunization and acute vaso-occlusive complications. Although increased echocardiography-derived tricuspid regurgitant jet velocity (TRV) was associated with the presence of RBC alloantibodies (P = 0.02), TRV was not significantly associated with alloimmunization when adjusted for patient age and number of transfused RBC units. Our study suggests that RBC antibody formation is significantly associated with older age of RBCs at the time of transfusion. Prospective studies in patients with SCD are required to confirm this finding.

Two cases of asymptomatic massive fetomaternal hemorrhage.

Evaluation of fetomaternal hemorrhage (FMH) in the immediate postpartum period is critical for the timely administration of Rh immunoglobulin (RhIG) prophylaxis to minimize the risk of alloimmunization in D-negative mothers of D-positive newborns. We report a series of two clinically-unsuspected cases of massive FMHs identified at our university medical center. Retrospective records of two cases of massive FMH were investigated using the electronic medical record. After positive fetal bleed screens, flow cytometric analysis for hemoglobin F was performed to quantify the volume of the hemorrhages in both cases. Flow cytometric enumeration with anti-D was also performed in one case. The two patients had 209.5 and 75 mL of fetal blood in circulation, resulting in 8 and 4 doses of RhIG administered, respectively. For the former patient, flow cytometric analysis with anti-D ruled out hereditary persistence of fetal hemoglobin and supported the fetal origin of the red cells. Due to the clinically-silent nature of both hemorrhages, further evaluation of the newborns' blood was not performed. These cases highlight the importance of rapidly obtaining accurate measurements of fetal blood loss via flow cytometric analysis in cases of FMH, particularly in clinically-unsuspected cases, to ensure timely administration of adequate immunoprophylaxis to D-negative mothers.