Bleeding risk and platelet transfusion refractoriness in patients with acute myelogenous leukemia who undergo autologous stem cell transplantation

Immunological platelet transfusion refractoriness: current insights from mechanisms to therapeutics

Although there have been tremendous improvements in the production and storage of platelets, platelet transfusion refractoriness (PTR) remains a serious clinical issue that may lead to various severe adverse events. The burden of supplying platelets is worsened by rising market demand and limited donor pools of compatible platelets. Antibodies against platelet antigens are known to activate platelets through FcγR-dependent or complement-activated channels, thereby rapidly eliminating foreign platelets. Recently, other mechanisms of platelet clearance have been reported. The current treatment strategy for PTR is to select appropriate and compatible platelets; however, this necessitates a sizable donor pool and technical assistance for costly testing. Consolidation of these mechanisms should be of critical significance in providing insight to establish novel therapeutics to target immunological platelet refractoriness. Therefore, the purposes of this review were to explore the modulation of the immune system over the activation and elimination of allogeneic platelets and to summarize the development of alternative approaches for treating and avoiding alloimmunization to human leukocyte antigen or human platelet antigen in PTR.

Impact of platelet transfusion refractoriness in the first 30 days post-hematopoietic stem cell transplantation on outcomes of patients with myelodysplastic syndrome

Introduction

Currently, no study has determined whether platelet transfusion refractoriness (PTR) post-hematopoietic stem cell transplantation (HSCT) before engraftment in patients with myelodysplastic syndrome (MDS) would impacts clinical outcomes.

Methods

We performed a MDS-specific retrospective analysis to determine whether PTR in one-month post-HSCT in patients with MDS could influence outcomes.

Results and discussion

Among the 315 patients enrolled, 110 (34.9 %) had PTR from stem cell infusion to one-month post-HSCT. Baseline characteristics of the PTR and non-PTR groups were similar. We found that patients with PTR had a slower and lower rate of platelet engraftment by day 28, as well as a slower recovery of neutrophils. The median days of neutrophil and platelet engraftment were 14 days (9-23) and 17 days (8-28) in the PTR groups versus 13 days (9-23) and 15 days (7-28) in the non-PTR group (P<0.001). By day 28, 84 of 110 patients (76.4%) with PTR achieved platelet engraftment compared with 181 of 205 patients (88.3%) without PTR achieving platelet engraftment (P=0.007). In addition, patients in the PTR group received significantly more red blood cell (median, 17 units vs. 10 units, P<0.001) and platelet transfusions (median, 13 units vs. 7 units, P<0.001). However, the overall survival was similar between the two groups. PTR in one-month post-HSCT, haploidentical donor, and ferritin level>1041ng/ml (median level) were independent adverse factors of platelet engraftment.

Anti-HLA Class I alloantibodies in platelet transfusion refractoriness: From mechanisms and determinants to therapeutic prospects

Patients with hematological disorders and severe thrombocytopenia require extensive and iterative platelet transfusion support. In these patients, platelet transfusion refractoriness represents a serious adverse transfusion event with major outcomes for patient care. Recipient alloantibodies against the donor HLA Class I antigens expressed at the cell surface of platelets result in a rapid removal of transfused platelets from the circulation and thus, therapeutic and prophylactic transfusion failure leading to a major bleeding risk. In this case, the only way to support the patient relies on the selection of HLA Class I compatible platelets, an approach restricted by the limited number of HLA-typed donors available and the difficulty of meeting the demand in an emergency. However, not all patients with anti-HLA Class I antibodies develop refractoriness to platelet transfusions, raising the question of the intrinsic characteristics of the antibodies and the immune-mediated mechanisms of platelet clearance associated with a refractory state. In this review, we examine the current challenges in platelet transfusion refractoriness and detail the key features of the antibodies involved that should be considered. Finally, we also provide an overview of future therapeutic strategies.

Altered Fc glycosylation of anti-HLA alloantibodies in hemato-oncological patients receiving platelet transfusions

BACKGROUND

The formation of alloantibodies directed against class I human leukocyte antigens (HLA) continues to be a clinically challenging complication after platelet transfusions, which can lead to platelet refractoriness (PR) and occurs in approximately 5%-15% of patients with chronic platelet support. Interestingly, anti-HLA IgG levels in alloimmunized patients do not seem to predict PR, suggesting functional or qualitative differences among anti-HLA IgG. The binding of these alloantibodies to donor platelets can result in rapid clearance after transfusion, presumably via FcγR-mediated phagocytosis and/or complement activation, which both are affected by the IgG-Fc glycosylation.

OBJECTIVES

To characterize the Fc glycosylation profile of anti-HLA class I antibodies formed after platelet transfusion and to investigate its effect on clinical outcome.

PATIENTS/METHODS

We screened and captured anti-HLA class I antibodies (anti-HLA A2, anti-HLA A24, and anti-HLA B7) developed after platelet transfusions in hemato-oncology patients, who were included in the PREPAReS Trial. Using liquid chromatography-mass spectrometry, we analyzed the glycosylation profiles of total and anti-HLA IgG1 developed over time. Subsequently, the glycosylation data was linked to the patients' clinical information and posttransfusion increments.

RESULTS

The glycosylation profile of anti-HLA antibodies was highly variable between patients. In general, Fc galactosylation and sialylation levels were elevated compared to total plasma IgG, which correlated negatively with the platelet count increment. Furthermore, high levels of afucosylation were observed for two patients.

CONCLUSIONS

These differences in composition of anti-HLA Fc-glycosylation profiles could potentially explain the variation in clinical severity between patients.

Evaluation of the effectiveness of platelet crossmatching by the solid-phase red cell adherence assay in adult patients of a tertiary care hospital in Thailand: A retrospective study

Background and Aims

Platelet transfusion refractoriness is well aware to be associated with poor clinical outcomes. Patients with the alloantibody causing refractoriness required cross-matched compatible products to improve the platelet number. This study aims to evaluate the effectiveness and availability of platelet crossmatching provided by the solid-phase red cell adherence (SPRCA) technique in the context of a tertiary university hospital.

Methods

A retrospective chart review was performed of the records of 214 patients with platelet refractoriness in Siriraj Hospital, a tertiary university hospital in Thailand, between January 1, 2017, and December 31, 2020.

Results

The SPRCA technique successfully provided cross-matched compatible platelets to 114 patients (69.7%). Platelet crossmatching significantly improved the platelet counts, as shown by the increased 1- and 24-h corrected-count increments (p< 0.0001). No acute transfusion reactions were observed in these patients. Of the 114 patients who received cross-matched platelets, 82 patients (71.9%) survived at 30-day posttransfusion; whereas, 16 patients (14.0%) died within 7-day posttransfusion.

Conclusion

The SPRCA method can provide a high availability rate of cross-matched platelets, which is effective at stopping and preventing clinical bleeding conditions. This method is appropriate to apply for platelet crossmatching in the context of a hospital blood bank.

Anchoring IgG-degrading enzymes to the surface of platelets selectively neutralizes antiplatelet antibodies

Immune thrombocytopenia (ITP) is an acquired bleeding disorder characterized by immunoglobulin G (IgG)-mediated platelet destruction. Current therapies primarily focus on reducing antiplatelet antibodies using immunosuppression or increasing platelet production with thrombopoietin mimetics. However, there are no universally safe and effective treatments for patients presenting with severe life-threatening bleeding. The IgG-degrading enzyme of Streptococcus pyogenes (IdeS), a protease with strict specificity for IgG, prevents IgG-driven immune disorders in murine models, including ITP. In clinical trials, IdeS prevented IgG-mediated kidney transplant rejection; however, the concentration of IdeS used to remove pathogenic antibodies causes profound hypogammaglobulinemia, and IdeS is immunogenic, which limits its use. Therefore, this study sought to determine whether targeting IdeS to FcγRIIA, a low-affinity IgG receptor on the surface of platelets, neutrophils, and monocytes, would be a viable strategy to decrease the pathogenesis of antiplatelet IgG and reduce treatment-related complications of nontargeted IdeS. We generated a recombinant protein conjugate by site-specifically linking the C-terminus of a single-chain variable fragment from an FcγRIIA antibody, clone IV.3, to the N-terminus of IdeS (scIV.3-IdeS). Platelets treated with scIV.3-IdeS had reduced binding of antiplatelet IgG from patients with ITP and decreased platelet phagocytosis in vitro, with no decrease in normal IgG. Treatment of mice expressing human FcγRIIA with scIV.3-IdeS reduced thrombocytopenia in a model of ITP and significantly improved the half-life of transfused platelets expressing human FcγRIIA. Together, these data suggest that scIV.3-IdeS can selectively remove pathogenic antiplatelet IgG and may be a potential treatment for patients with ITP and severe bleeding.

Prevalence, Risk Factors, and Outcomes of Platelet Transfusion Refractoriness in Critically Ill Patients: A Retrospective Cohort Study

Background

Refractoriness to platelet transfusion is an understudied phenomenon in critically ill patients. Our objective was to evaluate the prevalence, risk factors, and clinical outcomes of platelet refractoriness among patients in a tertiary-care intensive care unit (ICU).

Methods

A retrospective cohort study included all patients (age >14 years) who were admitted to a tertiary-care medical-surgical ICU between 2011 and 2016 and received ≥2 platelet transfusions during their ICU stay. We calculated platelet increment (PI) and corrected count increment (CCI).

Results

A total of 267 patients were enrolled in the study, collectively receiving 1357 transfusions with a median of 4.0 (interquartile range: 2.0, 6.0) transfusions per patient. The median pretransfusion platelet count was 31000.0 × 10⁶/L (interquartile range: 16000.0, 50000.0). The median PI was 6000 × 10⁶/L. The prevalence of platelet transfusion refractoriness was 54.8% based on PI < 10000 × 10⁶/L and 57.0% based on CCI <5000. Patients admitted under hepatology/liver transplant had the highest rates of platelet refractoriness (69.6%), while those under general surgery had the lowest rate (43.2%). Younger age, nontrauma admission, and larger spleen size were associated with platelet refractoriness. Finally, refractoriness was associated with increased length of stay in the ICU (p = 0.02), but not with mortality.

Conclusions

Platelet transfusion refractoriness was highly (>50%) prevalent in ICU patients. However, it was not associated with increased mortality.

An epitope-based approach of HLA-matched platelets for transfusion: a noninferiority crossover randomized trial

Platelet transfusion refractoriness results in adverse outcomes and increased health care costs. Managing refractoriness resulting from HLA alloimmunization necessitates the use of HLA antigen-matched platelets but requires a large platelet donor pool and does not guarantee full matching. We report the first randomized, double-blind, noninferiority, crossover trial comparing HLA epitope-matched (HEM) platelets with HLA standard antigen-matched (HSM) platelet transfusions. Alloimmunized, platelet-refractory, thrombocytopenic patients with aplastic anemia, myelodysplastic syndrome, or acute myeloid leukemia were eligible. HEM platelets were selected using HLAMatchMaker epitope (specifically eplet) matching. Patients received up to 8 prophylactic HEM and HSM transfusions provided in random order. The primary outcome was 1-hour posttransfusion platelet count increment (PCI). Forty-nine patients were randomized at 14 UK hospitals. For intention to treat, numbers of evaluable transfusions were 107 and 112 for HEM and HSM methods, respectively. Unadjusted mean PCIs for HEM and HSM methods were 23.9 (standard deviation [SD], 15) and 23.5 (SD, 14.1), respectively (adjusted mean difference, -0.1; 95% confidence interval [CI], -2.9 to 2.8). Because the lower limit of the 95% CI was not greater than the predefined noninferiority limit, the HEM approach was declared noninferior to the HSM approach. There were no differences in secondary outcomes of platelet counts, transfusion requirements, and bleeding events. Adequate 1-hour PCI was more frequently observed, with a mean number of 3.2 epitope mismatches, compared with 5.5 epitope mismatches for inadequate 1-hour increments. For every additional epitope mismatch, the likelihood of an adequate PCI decreased by 15%. Epitope-matched platelets should be considered to support HLA alloimmunized patients. This trial was registered at www.isrctn.com as #ISRCTN23996532.

Human Leukocyte Antigen Alloimmunization and Alloimmune Platelet Refractoriness

Despite significant advancements in the production of platelet products, storage, and transfusion, transfusion refractoriness remains a significant clinical problem, affecting up to 14% of hematological patients receiving platelet transfusions. Human leukocyte antigen (HLA) alloimmunization is a major cause of immune platelet refractoriness, and its rate can be significantly reduced by implementation of leukoreduction. Despite promising preclinical results, pathogen reduction does not reduce HLA alloimmunization. Patients with HLA alloimmune refractoriness are usually managed with HLA-selected platelet transfusions. In this review, we describe the pathophysiology of HLA alloimmunization and alloimmune refractoriness, as well as options to prevent and treat these transfusion complications. We discuss the evidence supporting these options and point out the outstanding gaps. Finally, we review the possible future directions for prevention and treatment of alloimmune refractoriness.

Is platelet monitoring during 7-day lusutrombopag treatment necessary in chronic liver disease patients with thrombocytopenia undergoing planned invasive procedures? A phase IIIb open-label study

AIM

Lusutrombopag is approved for thrombocytopenia in chronic liver disease patients planned to undergo invasive procedures. In previous clinical studies, lusutrombopag treatment was stopped in patients with an increase in platelet count (PC) of ≥20 × 10⁹ /L from baseline and whose PC was ≥50 × 10⁹ /L (discontinuation criteria). We assessed the influence of platelet monitoring during lusutrombopag treatment in lusutrombopag-naïve patients.

METHODS

In this open-label study, Child-Pugh class A and B (A/B) patients were enrolled and treated with lusutrombopag (3 mg/day) for 7 days. In the treatment-naïve A/B-1 group, the discontinuation criteria were applied on day 6. In the treatment-naïve A/B-2 group, the criteria were not applied. In a non-naïve A/B group, the criteria were applied on days 3 and 5-7. The main efficacy end-point was the proportion of patients without platelet transfusion (PT) before the primary invasive procedure.

RESULTS

In the A/B-1, A/B-2, and non-naïve A/B groups, the proportions of patients without PT were 80.9% (38/47), 83.0% (39/47), and 75.0% (6/8), respectively. The mean durations of PC ≥ 50 × 10⁹ /L without PT were 20.7, 20.3, and 22.8 days, respectively. Excessive PC increases (≥200 × 10⁹ /L) were not detected in any group. Treatment-related adverse events occurred in 4.3%, 6.4%, and 0% of A/B-1, A/B-2, and non-naïve A/B patients, respectively. Severe portal vein thrombosis occurred in one A/B-2 patient (PC 75 × 10⁹ /L at onset).

CONCLUSIONS

No meaningful efficacy and safety differences were observed among the groups with or without discontinuation criteria and the non-naïve group. These findings support lusutrombopag treatment without platelet monitoring and retreatment with lusutrombopag.

A systematic literature review on the use of platelet transfusions in patients with thrombocytopenia

Objective: Investigate globally, current treatment patterns, benefit-risk assessments, humanistic, societal and economic burden of platelet transfusion (PT). Methods: Publications from 1998 to June 27, 2018 were identified, based on databases searches including MEDLINE®; Embase and Cochrane Database of Systematic Reviews. Data from studies meeting pre-specified criteria were extracted and validated by independent reviewers. Data were obtained for efficacy and safety from randomized controlled trials (RCTs); data for epidemiology, treatment patterns, effectiveness, safety, humanistic and societal burden from real-world evidence (RWE) studies; and economic data from both. Results: A total of 3425 abstracts, 194 publications (190 studies) were included. PT use varied widely, from 0%-100% of TCP patients; 1.7%-24.5% in large studies (>1000 patients). Most were used prophylactically rather than therapeutically. 5 of 43 RCTs compared prophylactic PT with no intervention, with mixed results. In RWE studies PT generally increased platelet count (PC). This increase varied by patient characteristics and hence did not always translate into a clinically significant reduction in bleeding risk. Safety concerns included infection risk, alloimmunization and refractoriness with associated cost burden. Discussion: In RCTs and RWE studies there was significant heterogeneity in study design and outcome measures. In RWE studies, patients receiving PT may have been at higher risk than those not receiving PT creating potential bias. There were limited data on humanistic and societal burden. Conclusion: Although PTs are used widely for increasing PC in TCP, it is important to understand the limitations of PTs, and to explore the use of alternative treatment options where available.

Minimal invasive extracorporeal circulation preserves platelet function after cardiac surgery: a prospective observational study

Introduction:

Cardiac surgery on conventional cardiopulmonary bypass induces a combination of thrombocytopenia and platelet dysfunction which is strongly related to postoperative bleeding. Minimal invasive extracorporeal circulation has been shown to preserve coagulation integrity, though effect on platelet function remains unclear. We aimed to prospectively investigate perioperative platelet function in a series of patients undergoing cardiac surgery on minimal invasive extracorporeal circulation using point-of-care testing.

Methods:

A total of 57 patients undergoing elective cardiac surgery on minimal invasive extracorporeal circulation were prospectively recruited. Anticoagulation strategy was based on individualized heparin management and heparin level–guided protamine titration performed in all patients with a specialized point-of-care device (Hemostasis Management System – HMS Plus; Medtronic, Minneapolis, MN, USA). Platelet function was evaluated with impedance aggregometry using the ROTEM platelet (TEM International GmbH, Munich, Germany). ADPtest and TRAPtest values were assessed before surgery and after cardiopulmonary bypass.

Results:

ADPtest value was preserved during surgery on minimal invasive extracorporeal circulation (58.2 ± 20 U vs. 53.6 ± 21 U; p = 0.1), while TRAPtest was found significantly increased (90 ± 27 U vs. 103 ± 38 U; p = 0.03). Postoperative ADPtest and TRAPtest values were inversely related to postoperative bleeding (correlation coefficient: −0.29; p = 0.03 for ADPtest and correlation coefficient: −0.28; p = 0.04 for TRAPtest). The preoperative use of P2Y12 inhibitors was identified as the only independent predictor of a low postoperative ADPtest value (OR = 15.3; p = 0.02).

Conclusion:

Cardiac surgery on minimal invasive extracorporeal circulation is a platelet preservation strategy, which contributes to the beneficial effect of minimal invasive extracorporeal circulation in coagulation integrity.

HLA-Mediated Platelet Refractoriness

OBJECTIVES

To provide an overview of the complexities associated with the human leukocyte antigen (HLA)-mediated platelet refractoriness. HLA antibody detection technologies and limitations associated with methodologies are discussed.

METHODS

A case scenario and review of relevant literature describing platelet refractoriness are presented, followed by a discussion of HLA antibody testing.

RESULTS

Following diagnosis of HLA-mediated refractoriness, a decision is made regarding the approach to obtain the appropriate platelets. The panel reactive antibodies (PRA) % of the patient, HLA typing, and limitations of the HLA testing should be taken into account when deciding which type of product would be the best option for a given patient.

CONCLUSIONS

Following confirmation and review of HLA antibody testing, platelets are ordered based upon the PRA% and approach employed, HLA-matched platelets, antigen restricted platelets, or cross-matched platelets. The platelets are transfused and a posttransfusion increment count is monitored to determine transfusion success.

Allele and haplotype frequencies of human platelet and leukocyte antigens in platelet donors

OBJECTIVE

To described the allele and haplotype frequencies of human leukocyte antigen genes at the -A, -B loci and human platelet antigen genes for human platelet antigen systems 1 to 9, 11 and 15 in blood.

METHODS

We included 867 healthy unrelated volunteer donors who donated platelets between January 2011 and December 2014. Microarray genotyping was performed using a BeadChip microarray. Medium resolution typing of the human leukocyte antigen at loci A and B was carried out using sequence-specific oligonucleotide probe hybridization. We used multivariate analysis and our human leukocyte antigen population was compared to data from the United States national bone marrow donor program. Human platelet antigen results were compared to a literature review and data from around the world.

RESULTS

Our human leukocyte antigen haplotype results were more similar to those of hispanics, followed by caucasians. Likewise, our human platelet antigen sample is more similar to those of Argentina, Rio Grande do Sul and Italy.

CONCLUSION

This was the first article that discusses human platelet antigen and human leukocyte antigen data together. Rare genotypes or antibody associations can make patient management difficult. A blood bank with genotyped donors allows for optimal transfusion and can contribute to better results. Our information can serve as basis for a database of platelet antigen polymorphisms.

Avatrombopag Before Procedures Reduces Need for Platelet Transfusion in Patients With Chronic Liver Disease and Thrombocytopenia

BACKGROUND & AIMS

Patients with thrombocytopenia and chronic liver disease (CLD) may require platelet transfusions before scheduled procedures to decrease risk of bleeding. We performed 2 randomized, placebo-controlled, phase 3 trials in patients with thrombocytopenia and CLD undergoing scheduled procedures to evaluate the safety and efficacy of avatrombopag in increasing platelet counts in this patient population.

METHODS

In the ADAPT-1 and ADAPT-2 studies, adults with thrombocytopenia and CLD (n = 231 and n = 204, respectively) were in 1 of 2 cohorts according to their baseline platelet count (below 40 × 10⁹/L or 40 to below 50 × 10⁹/L) and within each cohort were randomized (2:1) to receive 5 daily doses of avatrombopag (60 mg if baseline platelet count below 40 × 10⁹/L or 40 mg if 40 to below 50 × 10⁹/L) or placebo. ADAPT-1 was conducted at 75 study sites in 20 countries, from February 2014 through January 2017, and ADAPT-2 was conducted at 74 sites in 16 countries, from December 2013 through January 2017. The primary endpoint was the proportion of patients not requiring platelet transfusions or rescue procedures for bleeding up to 7 days after a scheduled procedure.

RESULTS

In the ADAPT-1 study, 65.6% of patients who received 60 mg avatrombopag and 88.1% of patients who received 40 mg avatrombopag met the primary endpoint compared with 22.9% and 38.2% of patients receiving placebo, respectively (P < .0001 for both). In the ADAPT-2 study, 68.6% of patients who received 60 mg avatrombopag and 87.9% of patients who received 40 mg avatrombopag met the primary endpoint compared with 34.9% and 33.3% of patients who received placebo, respectively (P < .001 for both). Avatrombopag led to a measured increase in platelet counts and increased the proportion of patients who achieved the target platelet count ≥ 50 × 10⁹/L on procedure day vs placebo. The incidence and severity of adverse events were similar for the avatrombopag and placebo groups and were consistent with those expected in the CLD population.

CONCLUSIONS

In 2 phase 3 randomized trials, avatrombopag was superior to placebo in reducing the need for platelet transfusions or rescue procedures for bleeding in patients with thrombocytopenia and CLD undergoing a scheduled procedure. ClinicalTrials.gov nos.: NCT01972529 and NCT01976104.

Platelet Transfusion Refractoriness in Single-Unit Cord Blood Transplantation for Adults: Risk Factors and Clinical Outcomes

Platelet transfusion refractoriness (PTR) is frequently observed after allogeneic hematopoietic cell transplantation (HCT). However, the incidence of and risk factors for PTR, and impact of PTR on transplant outcomes after cord blood transplantation (CBT) have not been fully investigated. We retrospectively analyzed 185 adult patients who received single-unit CBT in our institute. The mean 16-hour corrected count increment (CCI) for the 5840 platelet transfusions was 3.68 × 10⁹/L. Among them, 3196 transfusions (54.7%) were associated with a PTR with 16-hour-CCI <4.5 × 10⁹/L. Results of multivariate analysis indicated that the following factors were significantly associated with decreased platelet transfusion responses: female sex with pregnancy history, male sex, the presence of HLA class I antibody, lower cord blood total nucleated cell dose, lower cord blood CD34⁺ cell dose, 3 locus HLA disparities, body temperature ≥38°C, C-reactive protein ≥10 mg/dL, cytomegalovirus reactivation, use of foscarnet, and use of liposomal amphotericin B. By contrast, graft-versus-host disease prophylaxis including methotrexate, ABO minor mismatch, use of ganciclovir, and use of linezolid were significantly associated with better platelet transfusion responses. PTR had a significant effect on poor neutrophil and platelet recovery, and overall mortality after CBT. These data suggest that early phase PTR may be predictive of engraftment and mortality after single-unit CBT for adults.

Factors influencing platelet transfusion refractoriness in patients undergoing allogeneic hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation has been considered a risk factor for development of platelet transfusion refractoriness. The objective of this study was to assess the platelet transfusion refractoriness rate in patients undergoing allogeneic hematopoietic stem cell transplantation from different sources. We retrospectively reviewed the charts and transfusion records of patients who underwent allogeneic stem cell transplantation at our institution between 2013 and 2015. The evaluation of post-transfusion platelet count was assessed for each transfusion given, from day of progenitor infusion to day 30 after transplantation. Of 167 patients included in this study, 101 received peripheral blood stem cell transplantation (PBSCT) and 66 received umbilical cord blood transplantation (UCBT). Overall, the percentage of platelet transfusions with a 14-h CCI lower than 5000 was 59.3%, being these data significantly higher for UCBT (67.6%) than for PBSCT (31.0%). Seventy-eight percent of patients underwent UCBT become refractory, while 38.6% of patients who received PBSCT were refractory. Factors associated to platelet refractoriness were lower CD34+ cell dose infused, higher number of antibiotics used, presence of anti-HLA I antibodies, and reduced-intensity conditioning regimen. Platelet refractoriness is a frequent and complex adverse event and remains a therapeutic challenge in the management of patients undergoing HSCT. There is a higher rate of platelet refractoriness in patients who received UCBT as compared to patients who received PBSCT.

Platelet transfusion refractoriness in patients with acute myeloid leukemia treated by intensive chemotherapy

Platelet transfusion refractoriness (PTR) is a major adverse event in the management of acute myeloid leukemia (AML). In a series of 897 adult patients with AML receiving intensive chemotherapy, we identified 41 patients (4.8%) with PTR. PTR was more frequently observed in parous women, patients with extra-medullary disease, a low white blood cell count, an infection, or hemophagocytic syndrome. Among the 31 patients with anti-human leucocyte antigen (HLA) antibodies, an HLA-matched donor was identified for 18 patients (58.1%). Median time between diagnosis of PTR and the first HLA-matched transfusion was 12.5days. HLA-matched transfusions induced a significant increment in platelet counts in 37% of cases. Thrombopoietin receptor agonists were given to 10 patients but did not shorten the duration of thrombocytopenia, reduce severe bleeding, or early death. Grade 3-4 bleeding events during induction, early death caused by bleeding, and death caused by bleeding at any time were significantly greater in patients that had platelet transfusion refractoriness (22% vs. 4.1%, P<0.0001; 12.2% vs. 1.4%, P=0.0006; and 24.4% vs. 5.3%, P<0.0001; respectively). PTR during chemotherapy for AML significantly increased the risk of early and late deaths caused by a severe bleeding event. Improved understanding of platelet destruction is needed to design mechanism-based therapeutic strategies.

Extended Small-Dose Platelet Transfusions in Multitransfused Hemato-Oncological Patients: A Single-Center Experience

BACKGROUND

Refractoriness to platelet transfusion, prevalent among 15-20% of hemato-oncological patients, is associated with multitransfusions and inferior outcomes. We evaluated the effectiveness of extended slow-dose transfusion (ESDT) in increasing platelet increments in multitransfused patients.

METHODS

Patients treated after the implementation of ESDT were compared with historical controls treated with standard single-donor platelet (SDP) transfusions. Cohorts of early and late recipients were assembled for comparison, i.e. the 8th or 9th and 11th platelet unit per patient, respectively. Patients in the ESDT group received transfusions equal to half an SDP unit, administered over 4 h. Effectiveness was defined as a higher corrected count increment (CCI) at 1, 12, and 24 h after transfusion.

RESULTS

In the early-recipients cohort, 24-h-posttransfusion increments were available for 29 ESDT patients and 6 standard patients, and did not differ significantly between the groups (p = 0.078). The 24-h-posttransfusion increment was available for 20 ESDT patients and 7 standard patients in the late-recipients cohort. The CCI was significantly higher in the ESDT group (p = 0.042). ABO compatibility improved the CCI (p = 0.01).

CONCLUSIONS

ESDT demonstrated slightly higher increments at 24 h after transfusion in late recipients, suggesting this could be a cost-effective approach for the treatment of thrombocytopenic multitransfused hemato-oncological patients.

CD8+ T cells mediate antibody-independent platelet clearance in mice

Platelet transfusion provides an important therapeutic intervention in the treatment and prevention of bleeding. However, some patients rapidly clear transfused platelets, preventing the desired therapeutic outcome. Although platelet clearance can occur through a variety of mechanisms, immune-mediated platelet removal often plays a significant role. Numerous studies demonstrate that anti-platelet alloantibodies can induce significant platelet clearance following transfusion. In fact, for nearly 50 years, anti-platelet alloantibodies were considered to be the sole mediator of immune-mediated platelet clearance in platelet-refractory individuals. Although nonimmune mechanisms of platelet clearance can often explain platelet removal in the absence of anti-platelet alloantibodies, many patients experience platelet clearance following transfusion in the absence of a clear mechanism. These results suggest that other processes of antibody-independent platelet clearance may occur. Our studies demonstrate that CD8(+)T cells possess the unique ability to induce platelet clearance in the complete absence of anti-platelet alloantibodies. These results suggest a previously unrecognized form of immune-mediated platelet clearance with significant implications in the appropriate management of platelet-refractory individuals.

Platelet refractoriness--practical approaches and ongoing dilemmas in patient management

Platelet refractoriness can represent a significant clinical problem that complicates the provision of platelet transfusions, is associated with adverse clinical outcomes and increases health care costs. Although it is most frequently due to non-immune platelet consumption, immunological factors are also often involved. Human leucocyte antigen (HLA) alloimmunization is the most important immune cause. Despite the fact that systematic reviews of the clinical studies evaluating different techniques for selecting HLA compatible platelets have not been powered to demonstrate improved clinical outcomes, platelet refractoriness is currently managed by the provision of HLA-matched or cross matched platelets. This review will address a practical approach to the diagnosis and management of platelet refractoriness while highlighting on-going dilemmas and knowledge gaps.

Efficacy of HLA-matched platelet transfusions for patients with hypoproliferative thrombocytopenia: a systematic review

BACKGROUND

HLA-matched platelets (PLTs) are widely used to transfuse patients but the effectiveness of HLA matching has not been well defined and the cost is approximately five times the cost of preparing the random-donor PLTs. The objective of this systematic review was to determine whether HLA-matched PLTs lead to a reduction in mortality; reduction in frequency or severity of hemorrhage; reduction in HLA alloimmunization, refractoriness, or PLT utilization; or improvement in PLT count increment in patients with hypoproliferative thrombocytopenia.

STUDY DESIGN AND METHODS

We conducted a literature search of MEDLINE, Cochrane Controlled Register of Clinical Trials, EMBASE, and PubMed databases to April 2012.

RESULTS

A total of 788 citations were reviewed and 30 reports were included in the analysis. Most studies did not include technologies currently in use for HLA typing or detection of HLA antibodies as 75% were conducted before the year 2000. None of the studies were adequately powered to detect an effect on mortality or hemorrhage. HLA-matched PLTs did not reduce alloimmunization and refractoriness rates beyond that offered by leukoreduction, and utilization was not consistently improved. HLA-matched PLTs led to better 1-hour posttransfusion count increments and percentage of PLT recovery in refractory patients; however, the effect at 24 hours was inconsistent.

CONCLUSION

The correlation of the PLT increment with other clinical outcomes and the effect of leukoreduction on HLA-matched PLT transfusion could not be determined. Prospective studies utilizing current technology and examining clinical outcomes are necessary to demonstrate the effectiveness of HLA-matched PLT transfusion.

The role of cytotoxic therapy with hematopoietic stem cell transplantation in the therapy of acute myelogenous leukemia in adults: an evidence-based review

Clinical research examining the role of hematopoietic stem cell transplantation (HSCT) in the therapy of acute myelogenous leukemia (AML) in adults is presented and critically evaluated in this systematic evidence-based review. Specific criteria were used for searching the published literature and for grading the quality and strength of the evidence and the strength of the treatment recommendations. Treatment recommendations based on the evidence are presented in Table 3, entitled Summary of Treatment Recommendations Made by the Expert Panel for Adult Acute Myelogenous Leukemia, and were reached unanimously by a panel of AML experts. The identified priority areas of needed future research in adult AML include: (1) What is the role of HSCT in treating patients with specific molecular markers (eg, FLT3, NPM1, CEBPA, BAALC, MLL, NRAS, etc.) especially in patients with normal cytogenetics? (2) What is the benefit of using HSCT to treat different cytogenetic subgroups? (3) What is the impact on survival outcomes of reduced intensity or nonmyeloablative versus conventional conditioning in older (>60 years) and intermediate (40-60 years) aged adults? (4) What is the impact on survival outcomes of unrelated donor HSCT vesus chemotherapy in younger (<40 years) adults with high risk disease?

Efficacy of prophylactic transfusions using single donor apheresis platelets versus pooled platelet concentrates in AML/MDS patients receiving allogeneic hematopoietic stem cell transplantation

Superiority of single-donor apheresis platelets (SDAP) over pooled platelet concentrates (PPC) transfusions is largely assumed, but unproven. We hypothesized that prophylactic SDAP and PPC transfusions are clinically equivalent after allogeneic hematopoietic stem cell transplants (HSCT). We studied all transfusions administered to 33 patients with AML/MDS during the first 100 days after busulfan-based, myeloablative HSCT. All donor-recipient pairs were ABO identical. Transfusion threshold was a platelet count < or =15 x 10(9)/l. The corrected increment (CCI) was used for all comparisons. Median time to platelet engraftment was 13 days (n=30). PPC transfusions (n=105) were ABO compatible, while 10% of 41 SDAP were not (P=0.006). Median post-transfusion platelet count was 51K/microl (5-118K) after SDAP and 36K/microl (3-115K) after PPC (P=0.0004). Median CCI was 14.178 (SDAP) versus 7.793 (PPC) (P=0.0001). Median time to another transfusion was 3 days (SDAP) and 2 days (PPC; P=0.3). In the week following any given transfusion, the median number of new transfusions was similar (n=2), as well as the need of further transfusion (16 versus 24%, P=0.2). A total of 17% of SDAP and 30% of PPC transfusions were labeled 'ineffective' (P=0.1). There were two non-lethal hemorrhage episodes (6%). SDAP transfusions produced better platelet counts, but SDAP and PPC were equally effective in preventing hemorrhage.

Universal prestorage leukoreduction in Canada decreases platelet alloimmunization and refractoriness

Randomized controlled trials have shown a reduction in platelet alloimmunization and refractoriness in patients with acute leukemia (AL) with the use of poststorage leukoreduction of blood products. Universal prestorage leukoreduction (ULR) of red cell and platelet products has been performed in Canada since August 1999. We conducted a retrospective analysis of 13 902 platelet transfusions in 617 patients undergoing chemotherapy (CT) for AL or stem cell transplantation (SCT) before (n = 315) and after (n = 302) the introduction of ULR. Alloimmunization was significantly reduced (19% to 7%, P <.001) in the post-ULR group. Alloimmune platelet refractoriness was similarly reduced (14% to 4%, P <.001). Fewer patients in the post-ULR group received HLA-matched platelets (14% vs 5%, P <.001). Alloimmunization and alloimmune refractoriness in the 318 patients who were previously pregnant and/or transfused were also reduced after ULR (P =.023 and P =.005, respectively). In a Cox regression model, the 3 independent factors that predicted for alloimmune refractoriness were nonleukoreduced blood products (relative risk [RR], 2.2 [95% CI, 1.2-4.3]), a history of pregnancy and/or transfusion (RR, 2.3 [95% CI, 1.3-4.2]), and receipt of 13 or more platelet transfusions (RR, 6.0 [95% CI, 2.4-15.3]). In conclusion, ULR reduces alloimmunization, refractoriness, and requirements for HLA-matched platelets when applied as routine transfusion practice to patients receiving CT or SCT.

Refractoriness to platelet transfusion

This review discusses the causes of refractoriness to platelet transfusions and presents three options for its management. Platelet refractoriness is a complication of platelet transfusion that affects variable proportions of patients, mostly depending on their diagnosis, previous immunologic stimuli, and type of blood products used for transfusion. A large recent study showed that platelet refractoriness develops in 13% of patients with acute leukemia transfused with traditional blood products and in 3 to 4% of recipients of white cell-reduced blood components. Options to manage platelet refractoriness include platelets from HLA-typed donors, platelet cross-matching, and the antibody specificity prediction method. The selection of the most convenient approach depends on local skills and the available economic and organizational resources. Finally, emerging concepts are presented which could impact the management of platelet refractoriness.

Factors influencing post-transfusional platelet increment in pediatric patients given hematopoietic stem cell transplantation

Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) always require platelet transfusions, but the increase in platelet count is often less than expected. Since factors responsible for poor response to platelet transfusions in this clinical setting are largely unknown, we performed a prospective study in 87 consecutive children transplanted in a single institution. The mean 16-h corrected count increment (CCI) of 598 platelet transfusions was 5.76 +/- 8.32 x 10(9)/l. Both before and after HSCT, 13.8% of patients had antibodies against HLA and/or platelet-specific antigens. Univariate analysis identified 12 factors significantly associated with a lower post-transfusion CCI, but only four reached statistical significance in the multivariate analysis. These four factors were concomitant therapy with vancomycin, alloimmunization, use of an Autopheresis cell separator for preparation of platelet concentrates and cytomegalovirus infection. We, therefore, suggest that a better response to platelet transfusions could be obtained by choosing a suitable cell separator, by avoiding the use of vancomycin and by adopting measures that reduce alloimmunization and CMV infection. Moreover, screening patients for HLA and platelet-specific antibodies before HSCT would identify the majority of subjects who will develop alloimmune refractoriness after transplantation and would allow the search for a compatible donor in advance.