Positive impacts of universal newborn screening on the outcome of children with sickle cell disease in the province of Quebec: A retrospective cohort study.

A universal newborn screening program for sickle cell disease (uNS-SCD) was implemented in the province of Québec (Qc) in November 2013, close in time to the recommendation of early initiation of hydroxyurea (HU) therapy for children. This retrospective cohort study evaluated the impact of such a program on children first seen between January 2000 and December 2019. Cohorts pre-SCD-uNS in Qc (pre-QcNS) (n = 253) and post-QcNS (n = 157) for patients seen prior to or after Nov 2013 were compared. Kaplan-Meier curves, Poisson regression, and logistic regressions were used for statistical analysis, using Software R version 4.2.1. Median age at first visit decreased significantly from 14.4 [interquartile range: 2.4-72.0] to 1.2 months [1.2-57.6] (p < 0.001). The percentage of children born in Qc undiagnosed at birth and referred after a first SCD-related complication dropped from 42.6% to 0.0% (p < 0.0001). The median age of HU introduction for patients with SS/Sß°-thalassemia decreased from 56.4 [31.2-96.0] to 9.0 months post-QcNS [8.0-12.1] (p < 0.001). Event-free survival improved significantly for any type of hospitalization as well as for vaso-occlusive crisis (VOC) (140-257 days (p < 0.001) and 1320 vs. 573 days (p < 0.002), respectively), resulting in a reduction from 2 [interquartile range: 1.0-3.0] to 1.0 hospitalizations/patient-year [0.6-1.4] (p < 0.001). Children with SS/Sß°-thalassemia referred post-QcNS also had fewer emergency department visits for VOC (RR: 0.69, 95% confidence interval: 0.54-0.88). The Universal NS program allows early detection and referral of children with SCD to comprehensive care centers. Earlier access ensures that children benefit from essential preventive interventions, reducing disease burden. This cohort study highlights that uNS-SCD is an essential public health measure.

Transfusing children with sickle cell disease using blood group genotyping when the pool of Black donors is limited.

BACKGROUND: Red blood cell transfusion is an effective treatment for patients with sickle cell disease (SCD). Alloimmunization can occur after a single transfusion, limiting further usage of blood transfusion. It is recommended to match for the ABO, D, C, E, and K antigens to reduce risks of alloimmunization. However, availability of compatible blood units can be challenging for blood providers with a limited number of Black donors. STUDY DESIGN AND METHODS: A prospective cohort of 205 pediatric patients with SCD was genotyped for the RH and FY genes. Transfusion and alloimmunization history were collected. Our capacity to find RhCE-matched donors was evaluated using a database of genotyped donors. RESULTS: Nearly 9.8% of patients carried a partial D variant and 5.9% were D-. Only 45.9% of RHCE alleles were normal, with the majority of variants affecting the RH5 (e) antigen. We found an alloimmunization prevalence of 20.7% and a Rh alloimmunization prevalence of 7.1%. Since Black donors represented only 1.40% of all blood donors in our province, D- Caucasian donors were mostly used to provide phenotype matched products. Compatible blood for patients with rare Rh variants was found only in Black donors. A donor with compatible RhCE could be identified for all patients. CONCLUSION: Although Rh-compatible donors were identified, blood units might not be available when needed and/or the extended phenotype or ABO group might not match the patient. A greater effort has to be made for the recruitment of Black donors to accommodate patients with SCD.

Quality of life and cost-effectiveness of convalescent plasma compared to standard care for hospitalized COVID-19 patients in the CONCOR-1 trial.

BACKGROUND: The CONvalescent Plasma for Hospitalized Adults With COVID-19 Respiratory Illness (CONCOR-1) trial was a multicenter randomized controlled trial assessing convalescent plasma in hospitalized COVID-19 patients. This study evaluates the cost-effectiveness of convalescent plasma and its impact on quality-of-life to provide insight into its potential as an alternative treatment in resource-constrained settings. METHODS: Individual patient data on health outcomes and resource utilization from the CONCOR-1 trial were used to conduct the analysis from the Canadian public payer's perspective with a time horizon of 30 days post-randomization. Baseline and 30-day EQ-5D-5L were measured to calculate quality-adjusted survival. All costs are presented in 2021 Canadian dollars. The base case assessed the EQ-5D-5L scores of hospitalized inpatients reporting at both timepoints, and a utility score of 0 was assigned for patients who died within 30 days. Costs for all patients enrolled were used. The sensitivity analysis utilizes EQ-5D-5L scores from the same population but only uses costs from this population. RESULTS: 940 patients were randomized: 627 received CCP and 313 received standard care. The total costs were $28,716 (standard deviation, $25,380) and $24,258 ($22,939) for the convalescent plasma and standard care arms respectively. EQ-5D-5L scores were 0.61 in both arms (p = .85) at baseline. At 30 days, EQ-5D-5L scores were 0.63 and 0.64 for patients in the convalescent plasma and standard care arms, respectively (p = .46). The incremental cost was $4458 and the incremental quality-adjusted life day was -0.078. DISCUSSION: Convalescent plasma was less effective and more costly than standard care in treating hospitalized COVID-19.

Management of a patient with sickle cell disease and multiple red blood cell alloantibodies in preparation for a hematopoietic stem cell transplantation.

BACKGROUND: Hematopoietic stem cell transplant (HSCT) is currently the only widely available curative option for patients with sickle cell disease (SCD). Alloimmunization in this population is frequent and can complicate transfusion management during the HSCT period. The case of a pediatric patient with severe SCD clinical phenotype, multiple alloantibodies (9), and hyperhemolysis syndrome who underwent haploidentical HSCT is described. STUDY DESIGN AND METHODS: The patient was known for an anti-e, despite RHCE*01.01 allele, which predicts a C- c+ E- weak e+ phenotype. Donors matching the patient's extended phenotype were targeted for RHCE genotyping. RESULTS: Donors homozygotes or heterozygotes for RHCE*01.01 were selected for compatibility analyses and ranked based on strength of reactions. Discordance between zygosity and strength of reactions was observed, as the most compatible donors were heterozygotes for RHCE*01.01. In total, the patient received seven RBC units from two different donors during HSCT process without transfusion reaction or development of new alloantibodies. Six months post-HSCT, his hemoglobin level is stable at around 120 g/L and his chimerism is 100%. DISCUSSION: This case highlights the complexity of transfusion management during HSCT of alloimmunized patients with SCD. Collecting sufficient compatible units requires early involvement of transfusion medicine teams and close communication with the local blood provider. Genotyping of donors self-identifying as Black is useful for identifying compatible blood for those patients but has some limitations. HSCT for heavily alloimmunized patients is feasible and safe with early involvement of transfusion medicine specialists. Further research on the clinical impact of genotypic matching is needed.

The selection and preparation of red cell components for intrauterine transfusion: A national survey.

BACKGROUND AND OBJECTIVES: The practice regarding the selection and preparation of red blood cells (RBCs) for intrauterine transfusion (IUT) is variable reflecting historical practice and expert opinion rather than evidence-based recommendations. The aim of this survey was to assess Canadian hospital blood bank practice with respect to red cell IUT. MATERIALS AND METHODS: A survey was sent to nine hospital laboratories known to perform red cell IUT. Questions regarding component selection, processing, foetal pre-transfusion testing, transfusion administration, documentation and traceability were assessed. RESULTS: The median annual number of IUTs performed in Canada was 109 (interquartile range, 103-118). RBC selection criteria included allogeneic, Cytomegalovirus seronegative, irradiated, fresh units with most sites preferentially providing HbS negative, group O, RhD negative, Kell negative and units lacking the corresponding maternal antibody without extended matching to the maternal phenotype. Red cell processing varied with respect to target haematocrit, use of saline reconstitution (n = 4), use of an automated procedure for red cell concentration (n = 1) and incorporation of a wash step (n = 2). Foetal pre-transfusion testing uniformly included haemoglobin measurement, but additional serologic testing varied. A variety of strategies were used to link the IUT event to the neonate post-delivery, including the creation of a unique foetal blood bank identifier at three sites. CONCLUSION: This survey reviews current practice and highlights the need for standardized national guidelines regarding the selection and preparation of RBCs for IUT. This study has prompted a re-examination of priorities for RBC selection for IUT and highlighted strategies for transfusion traceability in this unique setting.

Relevance of haemoglobin monitoring in apheresis plasma donors: A retrospective cohort study in Québec, Canada.

BACKGROUND AND OBJECTIVES: Systematically measuring pre-donation haemoglobin (Hb) levels might be overly cautious for apheresis plasma donation, since plasmapheresis entails a small loss of red blood cells. We explored the association between the frequency of apheresis plasma donation and capillary blood Hb levels. MATERIALS AND METHODS: This retrospective cohort study included donors who gave apheresis plasma at least twice between 24 October 2020 and 23 October 2022 in Québec, Canada. Results were stratified by sex and analysed with linear repeated-measure mixed models with random intercepts. RESULTS: In total, 9535 men (mean age = 46.7 years) and 9409 women (mean age = 41.1 years) made ≥2, but no more than 16 apheresis plasma donations. Over an average of 9.2 months of observation, men maintained Hb levels well above the Hb deferral threshold, and their Hb levels decreased by only 0.17 g/dL between the 1st and 15th donation return (p < 0.0001). Over an average of 9.0 months of observation, women also maintained adequate Hb levels, and their Hb levels decreased by 0.08 g/dL between the 1st and 15th donation return. CONCLUSION: The frequency of apheresis plasma donation was not associated with clinically meaningful changes in Hb levels, neither in men nor in women. This evidence questions the relevance of systematically monitoring Hb for apheresis plasma donation, at least for donation frequencies of ≤7-8 times per year. However, an adverse impact of plasmapheresis on Hb levels cannot be ruled out for individuals donating more frequently or for longer than ~9 months.

Incidence of acute haemolytic transfusion reaction among ABO-incompatible recipients transfused with A3 blood: A case series.

BACKGROUND AND OBJECTIVES: ABO antigens are among the most immunogenic, but the haemolytic risks of ABO incompatibilities involving a donor with a weak ABO phenotype are little documented. MATERIALS AND METHODS: This retrospective case series assessed the incidence of acute haemolytic transfusion reaction (AHTR) among ABO-incompatible recipients of A3 blood in Québec (Canada). Transfusion safety officers reported laboratory AHTR indicators measured ≤24 h pre- and post-transfusion. Because the AHTR case definition of Québec's Hemovigilance System (QHS) leaves significant room for clinical judgement, a two-step approach was used to assess potential cases: Step 1 consisted in a highly sensitive-but unspecific-initial screen that identified all candidate cases per QHS case definition, and Step 2 consisted in a detailed review of candidate cases by two haematologists. RESULTS: Nine donors initially typed as Group B (N = 1) or O (N = 8) were subsequently found to display an A3 B or A3 O phenotype. Eighty-one recipients received ABO-incompatible blood, including 53 (65.4%) with interpretable data. Of these, 29 (54.7%) were classified as candidate cases after Step 1. Following Step 2, no conclusive evidence of AHTR was found: Abnormal pre- versus post-transfusion changes appeared modest, within normal range, insufficient to ascertain AHTR, or were consistent with a pre-existing condition unrelated to AHTR. Two candidate cases had a QHS-reported transfusion reaction; both were unrelated to AHTR. CONCLUSION: In this case series, no conclusive evidence of serious AHTR was found among ABO-incompatible recipients who were inadvertently transfused with A3 blood.

Prevalence and determinants of anemia at discharge in pediatric intensive care survivors.

BACKGROUND: Restrictive transfusion practices are increasingly being followed in pediatric intensive care units (PICU); consequently, more patients are discharged anemic from PICU. Given the possible impact of anemia on long-term neurodevelopmental outcomes, we aim to describe the epidemiology of anemia at PICU discharge in a mixed (pediatric and cardiac) cohort of PICU survivors and to characterize risk factors for anemia. STUDY DESIGN AND METHODS: We performed a retrospective cohort study in the PICU of a multidisciplinary tertiary-care university-affiliated center. All consecutive PICU survivors for whom a hemoglobin level was available at PICU discharge were included. Baseline characteristics and hemoglobin levels were extracted from an electronic medical records database. RESULTS: From January 2013 to January 2018, 4750 patients were admitted to the PICU (97.1% survival); discharge hemoglobin levels were available for 4124 patients. Overall, 50.9% (n = 2100) were anemic at PICU discharge. Anemia at PICU discharge was also common in the cardiac surgery population (53.3%), mainly in acyanotic patients; only 24.6% of cyanotic patients were anemic according to standard definitions of anemia. Cardiac surgery patients were transfused more often and at higher hemoglobin levels than medical and non-cardiac surgery patients. Anemia at admission was the strongest predictor of anemia at discharge (odds ratios (OR): 6.51, 95% confidence interval (CI:5.40;7.85)). DISCUSSION: Half of PICU survivors are anemic at discharge. Further studies are required to determine the course of anemia after discharge and to ascertain whether anemia is associated with adverse long-term outcomes.

Comparison of Neutrophil Function in Granulocyte Concentrates From Prednisone- and G-CSF-Treated Donors: Effect of Stimulant, Leukapheresis and Storage.

Transfusion of granulocyte concentrates (GC) is an alternative therapy for neutropenic patients with life-threatening infections. While neutrophils are the main source of antimicrobial activity, only neutrophil numbers are used to certify GCs. The objective of this study was thus to functionally characterize neutrophils in GCs prepared by leukapheresis from G-CSF-stimulated donors and compare to the less characterized prednisone GCs. GCs prepared from healthy donors stimulated with prednisone and then G-CSF after a 6-month washout period were analyzed prior to and after leukapheresis, and after storage. Leukocyte composition, neutrophil viability, calcium mobilization, chemotaxis, phagocytosis, reactive oxygen species, cytokine production and metabolites were determined. G-CSF GCs contained significantly more neutrophils than prednisone GCs of which 40% were immature. In comparison to non-stimulated healthy donor neutrophils, prednisone GC neutrophils exhibited enhanced phagocytosis and G-CSF GC neutrophils showed decreased chemotaxis but increased IL-8 production. Leukapheresis altered prednisone GC neutrophil responses. Storage had a significant, negative impact on G-CSF GC neutrophils compared to prednisone GC neutrophils. G-CSF and prednisone GC neutrophils thus differ in maturity and function, and G-CSF GC neutrophils are more sensitive to storage. Functional testing of GC neutrophils and better storage conditions would improve the quality of this blood product.

Weak D type 42: Antigen density and risk of alloimmunization in the province of Québec.

BACKGROUND AND OBJECTIVES: A high proportion of suspected weak D patients referred to Héma-Québec were genotyped as weak D type 42 (368/2105, 17.5%). These patients are currently considered D with regard to RhD immunoprophylaxis in pregnancy and transfusion. The goal of this study was to retrospectively evaluate the risk of alloimmunization in weak D type 42 patients and to characterize their RhD surface molecule expression on red blood cells (RBCs) in comparison to other weak D types (1, 2 and 3). MATERIALS AND METHODS: A retrospective analysis using the weak D type 42 patients' medical data to verify potential anti-D alloimmunization events was conducted. Quantitative analyses using flow cytometry were also performed on RBCs to quantify the cell surface density of the D antigen. RESULTS: Data on 215 subjects with weak D type 42 were reviewed. None developed immune allo-anti-D; three had definite exposure to D+ red cells and 41 had possible exposure through pregnancy. Flow cytometry analysis showed that weak D types 1, 2, 3 and 42 had relative antigen densities of 2.7%, 2.2%, 8.1% and 3.6%, respectively, with R1R2 red cells referencing 100% density. The estimated antigen density range of weak D type 42 was 819-1104 sites per RBC. CONCLUSION: Our retrospective alloimmunization data analysis and antigen density study establish a basis for the consideration of a weak D type 42 individual as D+. This consideration would allow for a targeted reduction of RhD immunoprophylaxis in pregnancy and the unjustified use of D- units for transfusion.

Intravenous Immunoglobulin Use In Critically Ill Children.

Purpose: The use of intravenous immunoglobulins (IVIG) has increased significantly in the last decade causing challenges for blood suppliers to respond to the demand. Indications for which IVIG infusion should be given to critically ill children remain unclear. The objective of this study is to characterize the epidemiology of IVIG use in this population. Methods: We performed a single-center retrospective cohort study of all patients aged between 3 days and 18 years who received at least one IVIG infusion while hospitalized in the pediatric intensive care unit of the Centre hospitalier universitaire (CHU) Sainte-Justine, Montréal Quebec (Canada) between January 1, 2013 and December 31, 2018. Results: One hundred and seventy-two patients received a total of 342 IVIG infusions over the study period. Most common indications for IVIG infusions were staphylococcal or streptococcal toxic shock syndrome (n=53/342, 15.5%), immunoglobulin replacement in chylothorax (n=37/342, 10.9%), prophylaxis following bone marrow transplantation (n=31/342, 9.1%), myocarditis (n=25/342, 7.3%) and post-solid organ transplant complications (n=21/342, 6.1%). The median dose of IVIG per infusion was 0.95 g/kg (IQR 0.5-1.0) and median number of IVIG infusions per patient was one (IQR: 1-2). Seventy-nine percent of IVIG infusions given were administrated for off-label indications with regards to Health Canada recommendations. Conclusion: This study identified the most common indications for IVIG infusion in critically ill children in a tertiary care pediatric intensive care unit. Given the costs, the known adverse events associated with IVIG and the pressure that blood suppliers are facing to meet the demands, clinical trials are needed to evaluate the efficacy and safety of IVIG in conditions where use is significant.

Convalescent plasma for hospitalized patients with COVID-19: an open-label, randomized controlled trial.

The efficacy of convalescent plasma for coronavirus disease 2019 (COVID-19) is unclear. Although most randomized controlled trials have shown negative results, uncontrolled studies have suggested that the antibody content could influence patient outcomes. We conducted an open-label, randomized controlled trial of convalescent plasma for adults with COVID-19 receiving oxygen within 12 d of respiratory symptom onset ( NCT04348656 ). Patients were allocated 2:1 to 500 ml of convalescent plasma or standard of care. The composite primary outcome was intubation or death by 30 d. Exploratory analyses of the effect of convalescent plasma antibodies on the primary outcome was assessed by logistic regression. The trial was terminated at 78% of planned enrollment after meeting stopping criteria for futility. In total, 940 patients were randomized, and 921 patients were included in the intention-to-treat analysis. Intubation or death occurred in 199/614 (32.4%) patients in the convalescent plasma arm and 86/307 (28.0%) patients in the standard of care arm-relative risk (RR) = 1.16 (95% confidence interval (CI) 0.94-1.43, P = 0.18). Patients in the convalescent plasma arm had more serious adverse events (33.4% versus 26.4%; RR = 1.27, 95% CI 1.02-1.57, P = 0.034). The antibody content significantly modulated the therapeutic effect of convalescent plasma. In multivariate analysis, each standardized log increase in neutralization or antibody-dependent cellular cytotoxicity independently reduced the potential harmful effect of plasma (odds ratio (OR) = 0.74, 95% CI 0.57-0.95 and OR = 0.66, 95% CI 0.50-0.87, respectively), whereas IgG against the full transmembrane spike protein increased it (OR = 1.53, 95% CI 1.14-2.05). Convalescent plasma did not reduce the risk of intubation or death at 30 d in hospitalized patients with COVID-19. Transfusion of convalescent plasma with unfavorable antibody profiles could be associated with worse clinical outcomes compared to standard care.

Evaluation of Vaso-occlusive Crisis Management With Patient-Controlled Analgesia in Children With Sickle Cell Disease Requiring Hospitalization.

OBJECTIVE: The aim of this study was to review the use of patient-controlled analgesia (PCA) in sickle cell disease (SCD) for pediatric patients with vaso-occlusive crisis (VOC) in our institution and to compare the effect of early vs late PCA start on pain relief and LOS. METHODS: This retrospective study included all pediatric patients treated with PCA for a severe VOC from 2010 to 2016. "Early-PCA" was defined as start of PCA within 48 hours of arrival. Time to reach adequate analgesia was defined as the time to reach 2 consecutive pain scores less than 5/10 at 4-hour interval. RESULTS: During the study period, 46 patients presented 87 episodes of VOC treated with PCA. Sixty-three patients with VOC were treated with Early-PCA and 24 with Late-PCA. Both groups were comparable except for median pain score at admission; the Early-PCA group had higher scores: 9.0/10 vs 7.0/10. Time to reach adequate analgesia could be evaluated only in a subset of patients (n = 32) but was shorter in the Early-PCA group with a median difference of 41.0 hours (95% CI -82.0 to -6.0). Early-PCA was associated with a median reduction in LOS of 3.4 days (95% CI -4.9 to -1.9). There was no difference between the 2 groups in terms of side effects and occurrence of acute chest syndrome during hospitalization. CONCLUSIONS: In this study, a reduced time to reach adequate analgesia and LOS was noted in the Early-PCA group for severe VOC. A prospective study is required to confirm these results.

Association between Antiviral Prophylaxis and Cytomegalovirus and Epstein-Barr Virus DNAemia in Pediatric Recipients of Allogeneic Hematopoietic Stem Cell Transplant.

BACKGROUND: Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infections can have serious consequences during the period of aplasia and lymphopenia following hematopoietic stem cell transplantation (HSCT). Large pediatric cohort studies examining the effect of antiviral prophylaxis against these viruses are scarce. The present study aimed to analyse the potential effect of antiviral prophylaxis (acyclovir and famciclovir) on active post-transplant EBV and CMV infection in a pediatric cohort of allogeneic HSCT recipients. METHODS: We used data from the TREASuRE cohort, consisting of 156 patients who had a first allogeneic HSCT, enrolled in four pediatric centers in Canada between July 2013 and March 2017. Follow-up was performed from the time of transplant up to 100 days post-transplant. Adjusted hazard ratio (HR) with 95% confidence intervals (CI) for the association between antiviral prophylaxis with acyclovir and/or famciclovir and EBV and CMV DNAemia was estimated using multivariate Cox regression models. RESULTS: The post-transplant cumulative incidence of EBV and CMV DNAemia at 100 days of follow-up were, respectively, 34.5% (95% CI: 27.6-42.6) and 19.9% (95% CI: 14.5-27.1). For acyclovir, the adjusted hazard ratio (HR) for CMV and EBV DNAemia was 0.55 (95% CI: 0.24-1.26) and 1.41 (95% CI: 0.63-3.14), respectively. For famciclovir, the adjusted HR were 0.82 (95% CI: 0.30-2.29) and 0.79 (95% CI: 0.36-1.72) for CMV and EBV DNAemia, respectively. CONCLUSION: The antivirals famciclovir and acyclovir did not reduce the risk of post-transplant CMV and EBV DNAemia among HSCT recipients in our pediatric population.

High prevalence of weak D type 42 in a large-scale RHD genotyping program in the province of Quebec (Canada).

BACKGROUND: The determination of the RhD phenotype is crucial to avoid alloimmunization, especially in childbearing women. Following the 2015 recommendation from the Work Group on RHD Genotyping, a large-scale RHD genotyping program was implemented in the province of Quebec (Canada) and offered to women ≤45 years old with a serological weak D or discordant results. Since weak D type 42 was previously shown to be prevalent among French Canadians, genotyping for that variant was also performed. Our aim was to report the prevalence of the weak D alleles in the province of Quebec. STUDY DESIGN AND METHODS: A retrospective study of 2105 women with serological weak D referred to Hema-Quebec's immunohematology reference laboratory (IRL) between June 2016 and May 2020 was conducted. Results from the serological tests performed by the referring hospital were compiled and RHD were genotyped. RESULTS: Most patients presented at least one serological result ≤2+ before being referred to Hema-Quebec. Weak D type 42 was the most prevalent variant, representing 17.5% (368/2105) of all individuals tested. Only 15.3% (323/2105) of patients were weak D type 1, 3.3% (69/2105) were type 2, and 8.6% (180/2105) were type 3. Weak D type 42 is highly expressed in regions with low immigration rate and known for their founder effect. CONCLUSION: Our RHD genotyping program allowed for a better management of weak D. The province of Quebec presents a unique RHD genotype distribution. We confirmed that weak D type 42 is associated with a founder effect found in Caucasian French Canadians.

Risk factors for post-transplant Epstein-Barr virus events in pediatric recipients of hematopoietic stem cell transplants.

BACKGROUND: Epstein-Barr virus (EBV) can cause severe disease following hematopoietic stem cell transplant (HSCT), including post-transplant lymphoproliferative disorder (PTLD). The objective was to analyze risk factors associated with post-transplant EBV outcomes among pediatric allogeneic HSCT recipients. METHODS: We used data from 156 pediatric allogeneic HSCT recipients enrolled in the Canadian multicenter TREASuRE study. Cox and Prentice-Williams-Petersen models were used to analyze risk factors for post-transplant EBV events including occurrence and recurrence of EBV DNAemia, increase in EBV viral load (EBV-VL), and preemptive use of rituximab, an effective therapy against PTLD. RESULTS: Females were at higher risk for increasing EBV-VL (adjusted hazard ratio (HR) = 2.83 [95% confidence intervals (CI): 1.33-6.03]) and rituximab use (HR = 3.08 [1.14-8.30]), but had the same EBV DNAemia occurrence (HR = 1.21 [0.74-1.99]) and recurrence risks (HR=1.05 [0.70-1.58]) compared to males. EBV DNAemia was associated with recipient pre-transplant EBV seropositivity (HR = 2.47 [1.17-5.21]) and with graft from an EBV-positive donor (HR = 3.53 [1.95-6.38]). Anti-thymocyte globulin (ATG) was strongly associated with all EBV outcomes, including the use of rituximab (HR = 5.33 [1.47-19.40]). Mycophenolate mofetil (MMF) significantly decreased the risk of all EBV events including the rituximab use (HR = 0.13 [0.03-0.63]). CONCLUSION: This study in pediatric allogeneic HSCT patients reveals a reduced risk of all EBV outcomes with the use of MMF. Risk factors for EBV events such as EBV-VL occurrence and recurrence include EBV positivity in the donor and recipient, and use of ATG, whereas risk factors for the most severe forms of EBV outcome (EBV-VL and the use of rituximab) include female sex and ATG use.