The challenges of measuring bleeding outcomes in clinical trials of platelet transfusions

Prophylactic versus restrictive platelet transfusion strategy in patients with haematological malignancies in the ICU setting, a propensity-score analysis

PURPOSE

Prophylactic platelet transfusions (PT) aim to reduce bleeding. We assessed whether restrictive PT compared to prophylactic strategy could apply in ICU.

MATERIAL AND METHODS

We conducted a retrospective monocentric study including patients >18 yo with haematological malignancy admitted to the ICU with thrombocytopenia <20 G/L between 2018 and 2021. Patients were classified in 2 groups according transfusion strategy applied during the first 3 days: prophylactic or restrictive transfusion.

RESULTS

180 patients were included, 87 and 93 in the restrictive and prophylactic groups respectively. After propensity-score analysis, 2 groups of 54 matched patients were analyzed. Restrictive strategy led to a significant reduction in PT with incidence rate for 100-ICU-patients-days of 34.9 and 49.9, incidence rate ratio = 0.699 [0.5-0.9], p = 0.006, representing a 31% decrease. Decreased PT persisted until day 28 with platelet concentrates transfusions-free days at day 28 of 21 [13-25] and 16.5 [10.2-21] in the 2 groups (p = 0.04). Restrictive strategy did not result in higher grade ≥ 2 bleeding. Transfusion efficiency was low with similar number of days with platelet <10 or < 20 G/L regardless of strategy. Platelet transfusion strategy was not associated with 28-day mortality. Platelet nadir <5G/L was associated with day-28 mortality with HR = 1.882 [1.011-3.055], p = 0.046.

CONCLUSION

A restrictive PT strategy appears feasible in the ICU.

How I use platelet transfusions

Platelet transfusions are commonly administered for the prevention or treatment of bleeding in patients with acquired thrombocytopenia across a range of clinical contexts. Recent data, including randomized trials, have highlighted uncertainties in the risk-benefit balance of this therapy, which is the subject of this review. Hemovigilance systems report that platelets are the most frequently implicated component in transfusion reactions. There is considerable variation in platelet count increment after platelet transfusion, and limited evidence of efficacy for clinical outcomes, including prevention of bleeding. Bleeding events commonly occur despite the different policies for platelet transfusion prophylaxis. The underlying mechanisms of harm reported in randomized trials may be related to the role of platelets beyond hemostasis, including mediating inflammation. Research supports the implementation of a restrictive platelet transfusion policy. Research is needed to better understand the impact of platelet donation characteristics on outcomes, and to determine the optimal thresholds for platelet transfusion before invasive procedures or major surgery (eg, laparotomy). Platelet transfusion policies should move toward a risk-adapted approach that does not focus solely on platelet count.

Recommended primary outcomes for clinical trials evaluating hemostatic blood products and agents in patients with bleeding: Proceedings of a National Heart Lung and Blood Institute and US Department of Defense Consensus Conference

ABSTRACT

High-quality evidence guiding optimal transfusion and other supportive therapies to reduce bleeding is needed to improve outcomes for patients with either severe bleeding or hemostatic disorders that are associated with poor outcomes. Alongside challenges in performing high-quality clinical trials in patient populations who are at risk of bleeding or who are actively bleeding, the interpretation of research evaluating hemostatic agents has been limited by inconsistency in the choice of primary trial outcomes. This lack of standardization of primary endpoints or outcomes decreases the ability of clinicians to assess the validity of endpoints and compare research results across studies, impairs meta-analytic efforts, and, ultimately, delays the translation of research results into clinical practice. To address this challenge, an international panel of experts was convened by the National Heart Lung and Blood Institute and the US Department of Defense on September 23 and 24, 2019, to develop expert opinion, consensus-based recommendations for primary clinical trial outcomes for pivotal trials in pediatric and adult patients with six categories in various clinical settings. This publication documents the conference proceedings from the workshop funded by the National Heart Lung and Blood Institute and the US Department of Defense that consolidated expert opinion regarding clinically meaningful outcomes across a wide range of disciplines to provide guidance for outcomes of future trials of hemostatic products and agents for patients with active bleeding.

The role of platelets in bleeding in patients with thrombocytopenia and hematological disease

This review evaluates the role of platelets in bleeding risk among patients with hematological disease and thrombocytopenia. Platelets are pivotal in primary hemostasis, and possess non-hemostatic properties involved in angiogenesis, tissue repair, inflammation and metastatis. Also, platelets safeguard vascular integrity in inflamed vessels. Overall, bleeding risk depends on the underlying disease, and patients with cancer and platelet count <6-10 × 109/L have a markedly increased bleeding risk, while the platelet count does not correlate with bleeding risk at higher platelet counts. Other factors might affect platelet properties and thus bleeding risk, for example, drugs, low hematocrit, coagulation system impairments or transfusion of dysfunctional donor platelets. For patients with leukemia and immune thrombocytopenia, reduced platelet activation, platelet aggregation, or thrombopoiesis, reflected by the reduced presence of reticulated platelets, are associated with bleeding phenotype. However, mechanistic insight into the cause of reduced platelet function in different thrombocytopenic conditions is sparse, except for some inherited platelet disorders. Promising tools for platelet function studies in thrombocytopenia are flow cytometry and biomarker studies on platelet constituents. An important message from this current paper is that bleeding risk assessment must be tailored to specific patient populations and cannot be applied broadly to all patients with thrombocytopenia.

Bleeding Assessment Scale in Critically Ill Children (BASIC): Physician-Driven Diagnostic Criteria for Bleeding Severity

OBJECTIVE

Although bleeding frequently occurs in critical illness, no published definition to date describes the severity of bleeding accurately in critically ill children. We sought to develop diagnostic criteria for bleeding severity in critically ill children.

DESIGN

Delphi consensus process of multidisciplinary experts in bleeding/hemostasis in critically ill children, followed by prospective cohort study to test internal validity.

SETTING

PICU.

PATIENTS

Children at risk of bleeding in PICUs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twenty-four physicians worldwide (10 on a steering committee and 14 on an expert committee) from disciplines related to bleeding participated in development of a definition for clinically relevant bleeding. A provisional definition was created from 35 descriptors of bleeding. Using a modified online Delphi process and conference calls, the final definition resulted after seven rounds of voting. The Bleeding Assessment Scale in Critically Ill Children definition categorizes bleeding into severe, moderate, and minimal, using organ dysfunction, proportional changes in vital signs, anemia, and quantifiable bleeding. The criteria do not include treatments such as red cell transfusion or surgical interventions performed in response to the bleed. The definition was prospectively applied to 40 critically ill children with 46 distinct bleeding episodes. The kappa statistic between the two observers was 0.74 (95% CI, 0.57-0.91) representing substantial inter-rater reliability.

CONCLUSIONS

The Bleeding Assessment Scale in Critically Ill Children definition of clinically relevant bleeding severity is the first physician-driven definition applicable for bleeding in critically ill children derived via international expert consensus. The Bleeding Assessment Scale in Critically Ill Children definition includes clear criteria for bleeding severity in critically ill children. We anticipate that it will facilitate clinical communication among pediatric intensivists pertaining to bleeding and serve in the design of future epidemiologic studies if it is validated with patient outcomes.

Trends in platelet distributions from 2008 to 2017: a survey of twelve national and regional blood collectors

BACKGROUND

This multi-national study evaluated changes in platelet (PLT) unit distributions at 12 national or regional blood collectors over a 10-year period.

METHODS

Data on the total number of PLT distributions, the collection method, that is apheresis vs whole blood-derived (WBD), the PLT unit characteristics and post-collection modifications were obtained from 12 national or regional blood collectors from 2008 through 2017. Individual WBD PLT units were converted to apheresis equivalent units (i.e. a dose of PLTs) by dividing by 4, the typical pool size; WBD units that were pooled before distribution were counted as a single dose.

RESULTS

Overall at these 12 blood collectors, the total number of PLTs distributed in 2008 was 1 373 200, which rose by 10·2% to 1 513 803 in 2017. The Japanese Red Cross, which distributes only apheresis PLTs, had a 13·4% increase in the number of distributions between the years 2008 and 2017, while the other 11 blood collectors combined demonstrated a 6·8% increase in distributions between these two years. Between the years 2008 and 2017, the changes in the proportion of apheresis, platelet-rich plasma and buffy coat PLT distributions were -29·9%, -70·7% and 80·0%, respectively.

CONCLUSION

The number of PLT distributions increased during the 10-year study period despite prophylactic PLT transfusion thresholds having remained fairly consistent over the last decade. Perhaps this increase is in part driven by increased administration of platelets to patients with massive haemorrhage or an increase in stem cell transplantation. The use of buffy coat PLTs is increasing at these collectors.

The TREATT Trial (TRial to EvaluAte Tranexamic acid therapy in Thrombocytopenia): safety and efficacy of tranexamic acid in patients with haematological malignancies with severe thrombocytopenia: study protocol for a double-blind randomised controlled trial

Background

Patients with haematological malignancies often develop thrombocytopenia as a consequence of either their disease or its treatment. Platelet transfusions are commonly given to raise a low platelet count and reduce the risk of clinical bleeding (prophylaxis) or stop active bleeding (therapy). Recent studies have shown that many patients continue to experience bleeding despite the use of prophylactic platelet transfusions. Tranexamic acid is an anti-fibrinolytic, which reduces the breakdown of clots formed in response to bleeding. Anti-fibrinolytics have been shown to prevent bleeding, decrease blood loss and use of red cell transfusions in elective and emergency surgery, and are used widely in these settings. The aim of this trial is to test whether giving tranexamic acid to patients receiving treatment for haematological malignancies reduces the risk of bleeding or death and the need for platelet transfusions.

Methods

This is a multinational randomised, double-blind, placebo-controlled, parallel, superiority trial. Patients will be randomly assigned to receive tranexamic acid (given intravenously or orally) or a matching placebo in a 1:1 ratio, stratified by site. Patients with haematological malignancies receiving intensive chemotherapy or stem cell transplantation (or both) who are at least 18 years of age and expected to become severely thrombocytopenic for at least 5 days will be eligible for this trial. The primary outcome of the trial is the proportion of patients who died or had bleeding of World Health Organization grade 2 or above during the first 30 days of the trial. We will measure the rates of bleeding daily by using a short, structured assessment of bleeding, and we will record the number of transfusions given to patients. We will assess the risk of arterial and venous thrombosis for 120 days from the start of trial treatment.

Discussion

This trial will assess the safety and efficacy of using prophylactic tranexamic acid during a period of intensive chemotherapy and associated thrombocytopenia in people with haematological disorders.

Trial registration

This study was prospectively registered on Current Controlled Trials on 25 March 2015 (ISRCTN73545489) and is also registered on ClinicalTrials.gov (NCT03136445).

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3663-2) contains supplementary material, which is available to authorized users.

Prediction of bleeding by thromboelastography in ICU patients with haematological malignancy and severe sepsis

: ICU patients with haematological malignancy have an increased risk of bleeding. Recently, global haemostatic methods such as thromboelastography (TEG) have gained impact in evaluating coagulation. The aim of this study was to observe whether TEG could predict bleeding in haematological ICU patients with severe sepsis. Post-hoc single-centre analysis of patients with haematological malignancy included in the Scandinavian Starch for Severe Sepsis/Septic Shock (6S) trial. Clinical characteristics, TEG measurements and details regarding bleeding complications were retrieved from the 6S database. The association between TEG and bleeding were analysed by Cox regression and receiver operating characteristic curves. A total of 202 patients with severe sepsis were admitted to the ICU of Rigshospitalet, Copenhagen and included in the 6S trial. Forty-one had haematological malignancy and were analysed in the current study. During ICU stay, 20 patients (49%) had bleeding complications and 13 (32%) patients bled within the first 5 ICU days. We observed no associations between TEG and subsequent bleeding in Cox regression models. TEG variables at baseline had low predictive value for bleeding. Baseline TEG variables did not add value in identifying patients with high risk of bleeding in ICU patients with haematological malignancy and severe sepsis.

Hypoplastic thrombocytopenia and platelet transfusion: therapeutic goals

Platelet transfusions consist a major part of the management of hypoplastic thrombocytopenia, the latter occurring mainly among patients with hematological malignancies. Platelet transfusions have led to a reduction of deaths attributable to thrombocytopenia-induced bleeding, despite their possible complications; nonetheless, prophylactic administration of platelets to patients with severe thrombocytopenia or before invasive procedures should be based on specific criteria, as well as therapeutic administration during active bleeding. Recently developed ex-vivo procedures have resulted in producing safer blood products, yet it remains unclear whether these pathogen-inactivated products have sufficient efficacy. What is more, another significant problem that remains to be more effectively addressed is the developing refractoriness to platelet transfusions.

Comparison of a therapeutic-only versus prophylactic platelet transfusion policy for people with congenital or acquired bone marrow failure disorders

BACKGROUND

Bone marrow disorders encompass a group of diseases characterised by reduced production of red cells, white cells, and platelets, or defects in their function, or both. The most common bone marrow disorder is myelodysplastic syndrome. Thrombocytopenia, a low platelet count, commonly occurs in people with bone marrow failure. Platetet transfusions are routinely used in people with thrombocytopenia secondary to bone marrow failure disorders to treat or prevent bleeding. Myelodysplastic syndrome is currently the most common reason for receiving a platelet transfusion in some Western countries.

OBJECTIVES

To determine whether a therapeutic-only platelet transfusion policy (transfusion given when patient is bleeding) is as effective and safe as a prophylactic platelet transfusion policy (transfusion given to prevent bleeding according to a prespecified platelet threshold) in people with congenital or acquired bone marrow failure disorders.

SEARCH METHODS

We searched for randomised controlled trials (RCTs), non-RCTs, and controlled before-after studies (CBAs) in the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2017, Issue 9), Ovid MEDLINE (from 1946), Ovid Embase (from 1974), PubMed (e-publications only), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 12 October 2017.

SELECTION CRITERIA

We included RCTs, non-RCTs, and CBAs that involved the transfusion of platelet concentrates (prepared either from individual units of whole blood or by apheresis any dose, frequency, or transfusion trigger) and given to treat or prevent bleeding among people with congenital or acquired bone marrow failure disorders.We excluded uncontrolled studies, cross-sectional studies, and case-control studies. We excluded cluster-RCTs, non-randomised cluster trials, and CBAs with fewer than two intervention sites and two control sites due to the risk of confounding. We included all people with long-term bone marrow failure disorders that require platelet transfusions, including neonates. We excluded studies of alternatives to platelet transfusion, or studies of people receiving intensive chemotherapy or a stem cell transplant.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures outlined by Cochrane. Due to the absence of evidence we were unable to report on any of the review outcomes.

MAIN RESULTS

We identified one RCT that met the inclusion criteria for this review. The study enrolled only nine adults with MDS over a three-year study duration period. The trial was terminated due to poor recruitment rate (planned recruitment 60 participants over two years). Assessment of the risk of bias was not possible for all domains. The trial was a single-centre, single-blind trial. The clinical and demographic characteristics of the participants were never disclosed. The trial outcomes relevant to this review were bleeding assessments, mortality, quality of life, and length of hospital stay, but no data were available to report on any of these outcomes.We identified no completed non-RCTs or CBAs.We identified no ongoing RCTs, non-RCTs, or CBAs.

AUTHORS' CONCLUSIONS

We found no evidence to determine the safety and efficacy of therapeutic platelet transfusion compared with prophylactic platelet transfusion for people with long-term bone marrow failure disorders. This review underscores the urgency of prioritising research in this area. People with bone marrow failure depend on long-term platelet transfusion support, but the only trial that assessed a therapeutic strategy was halted. There is a need for good-quality studies comparing a therapeutic platelet transfusion strategy with a prophylactic platelet transfusion strategy; such trials should include outcomes that are important to patients, such as quality of life, length of hospital admission, and risk of bleeding.

Comparative assessment of prophylactic transfusions of platelet concentrates obtained by the PRP or buffy-coat methods, in patients undergoing allogeneic hematopoietic stem cell transplantation

OBJECTIVES

Whole blood-derived platelet concentrates can be obtained by the platelet-rich plasma (PRP-PCs) or the buffy-coat (BC-PCs) method. Few studies have shown that BC-PCs display lower in vitro platelet activation, but scarce information exists regarding transfusion efficacy. We have performed a retrospective study assessing platelet transfusion in patients undergoing allogeneic hematopoietic cell transplantation (AHCT) in our clinic, before and after the implementation of BC-PCs.

METHODS

We reviewed clinical records corresponding to 70 PRP-PCs and 86 BC-PCs prophylactic transfusions, which were performed to 55 AHCT patients. Transfusion efficacy was assessed by the 24-h post-transfusion corrected count increment (24-h CCI) and bleeding events. Clinical factors affecting transfusion outcome were also investigated.

RESULTS

Clinical characteristics and the total number of platelet transfusions were similar among groups. Mean donor exposure was 5.8 and 5.0 in each single PRP-PCs and BC-PCs transfusion, respectively (p < 0.01). The 24-h CCI was significantly higher in patients transfused with BC-PCs than in those receiving PRP-PCs (8.3[2.7-13.4] vs. 4.7[1.3-8.1]; p < 0.01). Independent predictors of poor platelet transfusion response included diagnosis other than acute leukemia (HR 8.30; 95% CI 1.96-35.22; p = 0.004), splenomegaly (HR 8.75; 95% CI 2.77-27.60; p < 0.001), graft versus host disease prophylaxis different from cyclosporine A and methotrexate (HR 3.96; 95% CI 1.55-10.14; p = 0.004) and PRP-PCs transfusion (HR 4.54; 95% CI 1.72-12.01; p = 0.002). There were no differences between both groups regarding the bleeding events.

CONCLUSION

In the AHCT setting, we hypothesize that BC-PCs transfusion, when compared to PRP-PCs, results in higher CCI and reduced donor exposure, but provides no significant benefit regarding bleeding outcome.

Factors related to the outcome of prophylactic platelet transfusions in patients with hematologic malignancies: an observational study

BACKGROUND

A better knowledge of the connections between platelet concentrate (PC) characteristics and transfusion outcomes in day-to-day practice would help improve the selection process of the most appropriate PC.

STUDY DESIGN AND METHODS

In this study of prophylactic platelet transfusions in patients with hematologic malignancies between 2002 and 2012, outcome criteria were corrected count increments (CCIs) and platelet transfusion intervals (TIs, in days). Studied characteristics were ABO matching status, platelet source, dose, storage duration, irradiation, washing, and transfusion sequence number (TSN). The analysis consisted of multivariable linear mixed-effects models with adjustments for patient diagnosis, sex, and type of treatment.

RESULTS

Overall, 869 patients and 6662 platelet transfusions were analyzed. For each day after the second day of storage, the CCI and TI decreased by 0.88 and 0.06 day, respectively. Compared to ABO-identical, transfusion with major ABO-incompatible PCs decreased the CCI and TI by 0.79 and 0.21 day, respectively. Platelet washing reduced the CCI and TI by 2.28 and 0.24 day, respectively. There was no significant association between platelet source or irradiation and CCI or TI. TI increased as the platelet dose per kg increased. Both CCI and TI decreased as the TSN increased.

CONCLUSION

Transfusion outcomes were significantly related to several PC-related factors. Associations for ABO matching status and storage duration were stronger than previously reported. Taking into account such factors when selecting a PC for transfusion could be beneficial to the recipient.

Risks of bleeding and thrombosis in intensive care unit patients with haematological malignancies

Background

Patients with malignant haematological disease and especially those who require intensive care have an increased risk of bleeding and thrombosis, but none of these data were obtained in ICU patients only. We assessed the incidence of bleeding and thrombotic complications, use of blood products and risk factors for bleeding in an adult population of ICU patients with haematological malignancies.

Methods

We screened all patients with acute leukaemia and myelodysplastic syndrome admitted to a university hospital ICU during 2008–2012. Bleeding in ICU was scored according to the WHO grading system, and risk factors were evaluated using unadjusted and adjusted analyses.

Results

In total, 116 of 129 ICU patients were included; their median length of stay was 7 (IQR 2–16) days. Of these, 66 patients (57%) had at least one bleeding episode in ICU; they bled for 3 (2–6) days and most often from lower and upper airways and upper GI tract. Thirty-nine (59%) of the 66 patients had severe or debilitating (WHO grade 3 or 4) bleeding. The median platelet count on the day of grade 3 or 4 bleeding was 23 × 10⁹ per litre (IQR 13–39). Nine patients (8%) died in ICU following a bleeding episode; five of these had intra-cerebral haemorrhage. Platelet count on admission was associated with subsequent bleeding (adjusted odds ratio 1.18 (95% CI 1.03–1.35) for every 10 × 10⁹ per litre drop in platelet count, p = 0.016). Eleven of the 116 patients (9%) developed a clinically significant thrombosis in ICU, which was the cause of death in four patients. The median platelet count was 20 × 10⁹ per litre (15–48) at the time of thrombosis. The patients received a median of 6 units of red blood cells, 1 unit of fresh frozen plasma and 8 units of platelet concentrates in ICU.

Conclusions

Severe and debilitating bleeding complications were frequent in our ICU patients with haematological malignancies, but thrombosis also occurred in spite of low platelet counts. Platelet count on ICU admission was associated with subsequent bleeding.

Electronic supplementary material

The online version of this article (10.1186/s13613-017-0341-y) contains supplementary material, which is available to authorized users.

Pathogen-reduced platelets for the prevention of bleeding

BACKGROUND

Platelet transfusions are used to prevent and treat bleeding in people who are thrombocytopenic. Despite improvements in donor screening and laboratory testing, a small risk of viral, bacterial, or protozoal contamination of platelets remains. There is also an ongoing risk from newly emerging blood transfusion-transmitted infections for which laboratory tests may not be available at the time of initial outbreak.One solution to reduce the risk of blood transfusion-transmitted infections from platelet transfusion is photochemical pathogen reduction, in which pathogens are either inactivated or significantly depleted in number, thereby reducing the chance of transmission. This process might offer additional benefits, including platelet shelf-life extension, and negate the requirement for gamma-irradiation of platelets. Although current pathogen-reduction technologies have been proven to reduce pathogen load in platelet concentrates, a number of published clinical studies have raised concerns about the effectiveness of pathogen-reduced platelets for post-transfusion platelet count recovery and the prevention of bleeding when compared with standard platelets.This is an update of a Cochrane review first published in 2013.

OBJECTIVES

To assess the effectiveness of pathogen-reduced platelets for the prevention of bleeding in people of any age requiring platelet transfusions.

SEARCH METHODS

We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 9), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 24 October 2016.

SELECTION CRITERIA

We included RCTs comparing the transfusion of pathogen-reduced platelets with standard platelets, or comparing different types of pathogen-reduced platelets.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We identified five new trials in this update of the review. A total of 15 trials were eligible for inclusion in this review, 12 completed trials (2075 participants) and three ongoing trials. Ten of the 12 completed trials were included in the original review. We did not identify any RCTs comparing the transfusion of one type of pathogen-reduced platelets with another.Nine trials compared Intercept® pathogen-reduced platelets to standard platelets, two trials compared Mirasol® pathogen-reduced platelets to standard platelets; and one trial compared both pathogen-reduced platelets types to standard platelets. Three RCTs were randomised cross-over trials, and nine were parallel-group trials. Of the 2075 participants enrolled in the trials, 1981 participants received at least one platelet transfusion (1662 participants in Intercept® platelet trials and 319 in Mirasol® platelet trials).One trial included children requiring cardiac surgery (16 participants) or adults requiring a liver transplant (28 participants). All of the other participants were thrombocytopenic individuals who had a haematological or oncological diagnosis. Eight trials included only adults.Four of the included studies were at low risk of bias in every domain, while the remaining eight included studies had some threats to validity.Overall, the quality of the evidence was low to high across different outcomes according to GRADE methodology.We are very uncertain as to whether pathogen-reduced platelets increase the risk of any bleeding (World Health Organization (WHO) Grade 1 to 4) (5 trials, 1085 participants; fixed-effect risk ratio (RR) 1.09, 95% confidence interval (CI) 1.02 to 1.15; I2 = 59%, random-effect RR 1.14, 95% CI 0.93 to 1.38; I2 = 59%; low-quality evidence).There was no evidence of a difference between pathogen-reduced platelets and standard platelets in the incidence of clinically significant bleeding complications (WHO Grade 2 or higher) (5 trials, 1392 participants; RR 1.10, 95% CI 0.97 to 1.25; I2 = 0%; moderate-quality evidence), and there is probably no difference in the risk of developing severe bleeding (WHO Grade 3 or higher) (6 trials, 1495 participants; RR 1.24, 95% CI 0.76 to 2.02; I2 = 32%; moderate-quality evidence).There is probably no difference between pathogen-reduced platelets and standard platelets in the incidence of all-cause mortality at 4 to 12 weeks (6 trials, 1509 participants; RR 0.81, 95% CI 0.50 to 1.29; I2 = 26%; moderate-quality evidence).There is probably no difference between pathogen-reduced platelets and standard platelets in the incidence of serious adverse events (7 trials, 1340 participants; RR 1.09, 95% CI 0.88 to 1.35; I2 = 0%; moderate-quality evidence). However, no bacterial transfusion-transmitted infections occurred in the six trials that reported this outcome.Participants who received pathogen-reduced platelet transfusions had an increased risk of developing platelet refractoriness (7 trials, 1525 participants; RR 2.94, 95% CI 2.08 to 4.16; I2 = 0%; high-quality evidence), though the definition of platelet refractoriness differed between trials.Participants who received pathogen-reduced platelet transfusions required more platelet transfusions (6 trials, 1509 participants; mean difference (MD) 1.23, 95% CI 0.86 to 1.61; I2 = 27%; high-quality evidence), and there was probably a shorter time interval between transfusions (6 trials, 1489 participants; MD -0.42, 95% CI -0.53 to -0.32; I2 = 29%; moderate-quality evidence). Participants who received pathogen-reduced platelet transfusions had a lower 24-hour corrected-count increment (7 trials, 1681 participants; MD -3.02, 95% CI -3.57 to -2.48; I2 = 15%; high-quality evidence).None of the studies reported quality of life.We did not evaluate any economic outcomes.There was evidence of subgroup differences in multiple transfusion trials between the two pathogen-reduced platelet technologies assessed in this review (Intercept® and Mirasol®) for all-cause mortality and the interval between platelet transfusions (favouring Intercept®).

AUTHORS' CONCLUSIONS

Findings from this review were based on 12 trials, and of the 1981 participants who received a platelet transfusion only 44 did not have a haematological or oncological diagnosis.In people with haematological or oncological disorders who are thrombocytopenic due to their disease or its treatment, we found high-quality evidence that pathogen-reduced platelet transfusions increase the risk of platelet refractoriness and the platelet transfusion requirement. We found moderate-quality evidence that pathogen-reduced platelet transfusions do not affect all-cause mortality, the risk of clinically significant or severe bleeding, or the risk of a serious adverse event. There was insufficient evidence for people with other diagnoses.All three ongoing trials are in adults (planned recruitment 1375 participants) with a haematological or oncological diagnosis.

Platelet function testing in pediatric patients

INTRODUCTION

Platelets play a key role in primary hemostasis and are also intricately linked to secondary hemostasis. Investigation of platelet function in children, especially in neonates, is seriously challenged by the volumes required to perform the majority of platelet function tests and due to the lack of standardization of these tests for use in children. Areas covered: The present review summarizes developmental hemostasis with a focus on the differences in platelet adhesion, activation and aggregation, between preterm neonates, full-term neonates, during childhood and in adults. Some of the most widely used platelet function tests are presented, including novel tests requiring only a small blood volume. Expert commentary: Currently available platelet function tests are limited as regards to investigation of neonates due to difficulties in obtaining adequate blood volume, poor standardization, lack of reference intervals for neonates and children, and an incomplete understanding of the functional phenotype of neonatal platelets, especially preterm neonatal platelets.

Rationale and design of platelet transfusions in haematopoietic stem cell transplantation: the PATH pilot study

INTRODUCTION

In patients with transient thrombocytopenia being treated with high-dose chemotherapy followed by stem cell rescue-haematopoietic stem cell transplantation (HSCT), prophylactic transfusions are standard therapy to prevent bleeding. However, a recent multicentre trial suggests that prophylactic platelet transfusions in HSCT may not be necessary. Additionally, the potential overuse of platelet products places a burden on a scarce healthcare resource. Moreover, the benefit of prophylactic platelet transfusions to prevent clinically relevant haemorrhage is debatable. Current randomised data compare different thresholds for administering prophylactic platelets or prophylactic versus therapeutic platelet transfusions. An alternative strategy involves prescribing prophylactic antifibrinolytic agents such as tranexamic acid to prevent bleeding.

METHODS AND ANALYSIS

This report describes the design of an open-labelled randomised pilot study comparing the prophylactic use of oral tranexamic acid with platelet transfusions in the setting of autologous HSCT. In 3-5 centres, 100 patients undergoing autologous HSCT will be randomly assigned to either a prophylactic tranexamic acid or prophylactic platelets bleeding prevention strategy-based daily platelet values up to 30 days post-transplant. The study will be stratified by centre and type of transplant. The primary goal is to demonstrate study feasibility while collecting clinical outcomes on (1) WHO and Bleeding Severity Measurement Scale (BSMS), (2) transplant-related mortality, (3) quality of life, (4) length of hospital stay, (5) intensive care unit admission rates, (6) Bearman toxicity scores, (7) incidence of infections, (8) transfusion requirements, (9) adverse reactions and (10) economic analyses.

ETHICS AND DISSEMINATION

This study is funded by a peer-reviewed grant from the Canadian Institutes of Health Research (201 503) and is registered on Clinicaltrials.gov NCT02650791. It has been approved by the Ottawa Health Science Network Research Ethics Board. Study results will presented at national and international conferences. Importantly, the results of this trial will inform the feasibility and conduct of a larger study.

TRIAL REGISTRATION NUMBER

NCT02650791; Pre-results.

Comparison of a therapeutic-only versus prophylactic platelet transfusion policy for people with congenital or acquired bone marrow failure disorders

This is the protocol for a review and there is no abstract. The objectives are as follows: To compare a therapeutic-only versus prophylactic platelet transfusion policy for people with myelodysplasia, inherited or acquired aplastic anaemia, and other congenital bone marrow failure disorders.

Alternatives, and adjuncts, to prophylactic platelet transfusion for people with haematological malignancies undergoing intensive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in people with thrombocytopenia. Although considerable advances have been made in platelet transfusion therapy since the mid-1970s, some areas continue to provoke debate especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.

OBJECTIVES

To determine whether agents that can be used as alternatives, or adjuncts, to platelet transfusions for people with haematological malignancies undergoing intensive chemotherapy or stem cell transplantation are safe and effective at preventing bleeding.

SEARCH METHODS

We searched 11 bibliographic databases and four ongoing trials databases including the Cochrane Central Register of Controlled Trials (CENTRAL, 2016, Issue 4), MEDLINE (OvidSP, 1946 to 19 May 2016), Embase (OvidSP, 1974 to 19 May 2016), PubMed (e-publications only: searched 19 May 2016), ClinicalTrials.gov, World Health Organization (WHO) ICTRP and the ISRCTN Register (searched 19 May 2016).

SELECTION CRITERIA

We included randomised controlled trials in people with haematological malignancies undergoing intensive chemotherapy or stem cell transplantation who were allocated to either an alternative to platelet transfusion (artificial platelet substitutes, platelet-poor plasma, fibrinogen concentrate, recombinant activated factor VII, desmopressin (DDAVP), or thrombopoietin (TPO) mimetics) or a comparator (placebo, standard care or platelet transfusion). We excluded studies of antifibrinolytic drugs, as they were the focus of another review.

DATA COLLECTION AND ANALYSIS

Two review authors screened all electronically derived citations and abstracts of papers identified by the review search strategy. Two review authors assessed risk of bias in the included studies and extracted data independently.

MAIN RESULTS

We identified 16 eligible trials. Four trials are ongoing and two have been completed but the results have not yet been published (trial completion dates: April 2012 to February 2017). Therefore, the review included 10 trials in eight references with 554 participants. Six trials (336 participants) only included participants with acute myeloid leukaemia undergoing intensive chemotherapy, two trials (38 participants) included participants with lymphoma undergoing intensive chemotherapy and two trials (180 participants) reported participants undergoing allogeneic stem cell transplantation. Men and women were equally well represented in the trials. The age range of participants included in the trials was from 16 years to 81 years. All trials took place in high-income countries. The manufacturers of the agent sponsored eight trials that were under investigation, and two trials did not report their source of funding.No trials assessed artificial platelet substitutes, fibrinogen concentrate, recombinant activated factor VII or desmopressin.Nine trials compared a TPO mimetic to placebo or standard care; seven of these used pegylated recombinant human megakaryocyte growth and differentiation factor (PEG-rHuMGDF) and two used recombinant human thrombopoietin (rhTPO).One trial compared platelet-poor plasma to platelet transfusion.We considered that all the trials included in this review were at high risk of bias and meta-analysis was not possible in seven trials due to problems with the way data were reported.We are very uncertain whether TPO mimetics reduce the number of participants with any bleeding episode (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.10 to 1.62, one trial, 120 participants, very low quality evidence). We are very uncertain whether TPO mimetics reduce the risk of a life-threatening bleed after 30 days (OR 1.46, 95% CI 0.06 to 33.14, three trials, 209 participants, very low quality evidence); or after 90 days (OR 1.00, 95% CI 0.06 to 16.37, one trial, 120 participants, very low quality evidence). We are very uncertain whether TPO mimetics reduce platelet transfusion requirements after 30 days (mean difference -3.00 units, 95% CI -5.39 to -0.61, one trial, 120 participants, very low quality evidence). No deaths occurred in either group after 30 days (one trial, 120 participants, very low quality evidence). We are very uncertain whether TPO mimetics reduce all-cause mortality at 90 days (OR 1.00, 95% CI 0.24 to 4.20, one trial, 120 participants, very low quality evidence). No thromboembolic events occurred for participants treated with TPO mimetics or control at 30 days (two trials, 209 participants, very low quality evidence). We found no trials that looked at: number of days on which bleeding occurred, time from randomisation to first bleed or quality of life.One trial with 18 participants compared platelet-poor plasma transfusion with platelet transfusion. We are very uncertain whether platelet-poor plasma reduces the number of participants with any bleeding episode (OR 16.00, 95% CI 1.32 to 194.62, one trial, 18 participants, very low quality evidence). We are very uncertain whether platelet-poor plasma reduces the number of participants with severe or life-threatening bleeding (OR 4.00, 95% CI 0.56 to 28.40, one trial, 18 participants, very low quality evidence). We found no trials that looked at: number of days on which bleeding occurred, time from randomisation to first bleed, number of platelet transfusions, all-cause mortality, thromboembolic events or quality of life.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine if platelet-poor plasma or TPO mimetics reduce bleeding for participants with haematological malignancies undergoing intensive chemotherapy or stem cell transplantation. To detect a decrease in the proportion of participants with clinically significant bleeding from 12 in 100 to 6 in 100 would require a trial containing at least 708 participants (80% power, 5% significance). The six ongoing trials will provide additional information about the TPO mimetic comparison (424 participants) but this will still be underpowered to demonstrate this level of reduction in bleeding. None of the included or ongoing trials include children. There are no completed or ongoing trials assessing artificial platelet substitutes, fibrinogen concentrate, recombinant activated factor VII or desmopressin in people undergoing intensive chemotherapy or stem cell transplantation for haematological malignancies.

A study protocol for a randomised controlled trial evaluating clinical effects of platelet transfusion products: the Pathogen Reduction Evaluation and Predictive Analytical Rating Score (PREPAReS) trial

INTRODUCTION

Patients with chemotherapy-induced thrombocytopaenia frequently experience minor and sometimes severe bleeding complications. Unrestrictive availability of safe and effective blood products is presumed by treating physicians as well as patients. Pathogen reduction technology potentially offers the opportunity to enhance safety by reducing bacterial and viral contamination of platelet products along with a potential reduction of alloimmunisation in patients receiving multiple platelet transfusions.

METHODS AND ANALYSIS

To test efficacy, a randomised, single-blinded, multicentre controlled trial was designed to evaluate clinical non-inferiority of pathogen-reduced platelet concentrates treated by the Mirasol system, compared with standard plasma-stored platelet concentrates using the percentage of patients with WHO grade ≥ 2 bleeding complications as the primary endpoint. The upper limit of the 95% CI of the non-inferiority margin was chosen to be a ≤ 12.5% increase in this percentage. Bleeding symptoms are actively monitored on a daily basis. The adjudication of the bleeding grade is performed by 3 adjudicators, blinded to the platelet product randomisation as well as by an automated computer algorithm. Interim analyses evaluating bleeding complications as well as serious adverse events are performed after each batch of 60 patients. The study started in 2010 and patients will be enrolled up to a maximum of 618 patients, depending on the results of consecutive interim analyses. A flexible stopping rule was designed allowing stopping for non-inferiority or futility. Besides analysing effects of pathogen reduction on clinical efficacy, the Pathogen Reduction Evaluation and Predictive Analytical Rating Score (PREPAReS) is designed to answer several other pending questions and translational issues related to bleeding and alloimmunisation, formulated as secondary and tertiary endpoints.

ETHICS AND DISSEMINATION

Ethics approval was obtained in all 3 participating countries. Results of the main trial and each of the secondary endpoints will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NTR2106; Pre-results.

Comparison of different platelet count thresholds to guide administration of prophylactic platelet transfusion for preventing bleeding in people with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in people who are thrombocytopenic due to bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004, and previously updated in 2012 that addressed four separate questions: prophylactic versus therapeutic-only platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. This review has now been split into four smaller reviews looking at these questions individually; this review compares prophylactic platelet transfusion thresholds.

OBJECTIVES

To determine whether different platelet transfusion thresholds for administration of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect the efficacy and safety of prophylactic platelet transfusions in preventing bleeding in people with haematological disorders undergoing myelosuppressive chemotherapy or haematopoietic stem cell transplantation (HSCT).

SEARCH METHODS

We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library 2015, Issue 6, 23 July 2015), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

We included RCTs involving transfusions of platelet concentrates, prepared either from individual units of whole blood or by apheresis, and given to prevent bleeding in people with haematological disorders (receiving myelosuppressive chemotherapy or undergoing HSCT) that compared different thresholds for administration of prophylactic platelet transfusions (low trigger (5 x 10(9)/L); standard trigger (10 x 10(9)/L); higher trigger (20 x 10(9)/L, 30 x 10(9)/L, 50 x 10(9)/L); or alternative platelet trigger (for example platelet mass)).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

Three trials met our predefined inclusion criteria and were included for analysis in the review (499 participants). All three trials compared a standard trigger (10 x 10(9)/L) versus a higher trigger (20 x 10(9)/L or 30 x 10(9)/L). None of the trials compared a low trigger versus a standard trigger or an alternative platelet trigger. The trials were conducted between 1991 and 2001 and enrolled participants from fairly comparable patient populations.The original review contained four trials (658 participants); in the previous update of this review we excluded one trial (159 participants) because fewer than 80% of participants had a haematological disorder. We identified no new trials in this update of the review.Overall, the methodological quality of the studies was low across different outcomes according to GRADE methodology. None of the included studies were at low risk of bias in every domain, and all the included studies had some threats to validity.Three studies reported the number of participants with at least one clinically significant bleeding episode within 30 days from the start of the study. There was no evidence of a difference in the number of participants with a clinically significant bleeding episode between the standard and higher trigger groups (three studies; 499 participants; risk ratio (RR) 1.35, 95% confidence interval (CI) 0.95 to 1.90; low-quality evidence).One study reported the number of days with a clinically significant bleeding event (adjusted for repeated measures). There was no evidence of a difference in the number of days of bleeding per participant between the standard and higher trigger groups (one study; 255 participants; relative proportion of days with World Health Organization Grade 2 or worse bleeding (RR 1.71, 95% CI 0.84 to 3.48, P = 0.162; authors' own results; low-quality evidence).Two studies reported the number of participants with severe or life-threatening bleeding. There was no evidence of any difference in the number of participants with severe or life-threatening bleeding between a standard trigger level and a higher trigger level (two studies; 421 participants; RR 0.99, 95% CI 0.52 to 1.88; low-quality evidence).Only one study reported the time to first bleeding episode. There was no evidence of any difference in the time to the first bleeding episode between a standard trigger level and a higher trigger level (one study; 255 participants; hazard ratio 1.11, 95% CI 0.64 to 1.91; low-quality evidence).Only one study reported on all-cause mortality within 30 days from the start of the study. There was no evidence of any difference in all-cause mortality between standard and higher trigger groups (one study; 255 participants; RR 1.78, 95% CI 0.83 to 3.81; low-quality evidence).Three studies reported on the number of platelet transfusions per participant. Two studies reported on the mean number of platelet transfusions per participant. There was a significant reduction in the number of platelet transfusions per participant in the standard trigger group (two studies, mean difference -2.09, 95% CI -3.20 to -0.99; low-quality evidence).One study reported on the number of transfusion reactions. There was no evidence to demonstrate any difference in transfusion reactions between the standard and higher trigger groups (one study; 79 participants; RR 0.07, 95% CI 0.00 to 1.09).None of the studies reported on quality of life.

AUTHORS' CONCLUSIONS

In people with haematological disorders who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT, we found low-quality evidence that a standard trigger level (10 x 10(9)/L) is associated with no increase in the risk of bleeding when compared to a higher trigger level (20 x 10(9)/L or 30 x 10(9)/L). There was low-quality evidence that a standard trigger level is associated with a decreased number of transfusion episodes when compared to a higher trigger level (20 x 10(9)/L or 30 x 10(9)/L).Findings from this review were based on three studies and 499 participants. Without further evidence, it is reasonable to continue with the current practice of administering prophylactic platelet transfusions using the standard trigger level (10 x 10(9)/L) in the absence of other risk factors for bleeding.

Improving platelet transfusion safety: biomedical and technical considerations

Platelet concentrates account for near 10% of all labile blood components but are responsible for more than 25% of the reported adverse events. Besides factors related to patients themselves, who may be particularly at risk of side effects because of their underlying illness, there are aspects of platelet collection and storage that predispose to adverse events. Platelets for transfusion are strongly activated by collection through disposal equipment, which can stress the cells, and by preservation at 22 °C with rotation or rocking, which likewise leads to platelet activation, perhaps more so than storage at 4 °C. Lastly, platelets constitutively possess a very large number of bioactive components that may elicit pro-inflammatory reactions when infused into a patient. This review aims to describe approaches that may be crucial to minimising side effects while optimising safety and quality. We suggest that platelet transfusion is complex, in part because of the complexity of the "material" itself: platelets are highly versatile cells and the transfusion process adds a myriad of variables that present many challenges for preserving basal platelet function and preventing dysfunctional activation of the platelets. The review also presents information showing--after years of exhaustive haemovigilance--that whole blood buffy coat pooled platelet components are extremely safe compared to the gold standard (i.e. apheresis platelet components), both in terms of acquired infections and of immunological/inflammatory hazards.

Different doses of prophylactic platelet transfusion for preventing bleeding in people with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in people who are thrombocytopenic due to bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004, and updated in 2012 that addressed four separate questions: prophylactic versus therapeutic-only platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. This review has now been split into four smaller reviews; this review compares different platelet transfusion doses.

OBJECTIVES

To determine whether different doses of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect their efficacy and safety in preventing bleeding in people with haematological disorders undergoing myelosuppressive chemotherapy with or without haematopoietic stem cell transplantation (HSCT).

SEARCH METHODS

We searched for randomised controlled trials in the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library 2015, Issue 6), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

Randomised controlled trials involving transfusions of platelet concentrates, prepared either from individual units of whole blood or by apheresis, and given to prevent bleeding in people with malignant haematological disorders or undergoing HSCT that compared different platelet component doses (low dose 1.1 x 10(11)/m(2) ± 25%, standard dose 2.2 x 10(11)/m(2) ± 25%, high dose 4.4 x 10(11)/m(2) ± 25%).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included seven trials (1814 participants) in this review; six were conducted during one course of treatment (chemotherapy or HSCT).Overall the methodological quality of studies was low to moderate across different outcomes according to GRADE methodology. None of the included studies were at low risk of bias in every domain, and all the included studies had some threats to validity.Five studies reported the number of participants with at least one clinically significant bleeding episode within 30 days from the start of the study. There was no difference in the number of participants with a clinically significant bleeding episode between the low-dose and standard-dose groups (four studies; 1170 participants; risk ratio (RR) 1.04, 95% confidence interval (CI) 0.95 to 1.13; moderate-quality evidence); low-dose and high-dose groups (one study; 849 participants; RR 1.02, 95% CI 0.93 to 1.11; moderate-quality evidence); or high-dose and standard-dose groups (two studies; 951 participants; RR 1.02, 95% CI 0.93 to 1.11; moderate-quality evidence).Three studies reported the number of days with a clinically significant bleeding event per participant. There was no difference in the number of days of bleeding per participant between the low-dose and standard-dose groups (two studies; 230 participants; mean difference -0.17, 95% CI -0.51 to 0.17; low quality evidence). One study (855 participants) showed no difference in the number of days of bleeding per participant between high-dose and standard-dose groups, or between low-dose and high-dose groups (849 participants).Three studies reported the number of participants with severe or life-threatening bleeding. There was no difference in the number of participants with severe or life-threatening bleeding between a low-dose and a standard-dose platelet transfusion policy (three studies; 1059 participants; RR 1.33, 95% CI 0.91 to 1.92; low-quality evidence); low-dose and high-dose groups (one study; 849 participants; RR 1.20, 95% CI 0.82 to 1.77; low-quality evidence); or high-dose and standard-dose groups (one study; 855 participants; RR 1.11, 95% CI 0.73 to 1.68; low-quality evidence).Two studies reported the time to first bleeding episodes; we were unable to perform a meta-analysis. Both studies (959 participants) individually found that the time to first bleeding episode was either the same, or longer, in the low-dose group compared to the standard-dose group. One study (855 participants) found that the time to the first bleeding episode was the same in the high-dose group compared to the standard-dose group.Three studies reported all-cause mortality within 30 days from the start of the study. There was no difference in all-cause mortality between treatment arms (low-dose versus standard-dose: three studies; 1070 participants; RR 2.04, 95% CI 0.70 to 5.93; low-quality evidence; low-dose versus high-dose: one study; 849 participants; RR 1.33, 95% CI 0.50 to 3.54; low-quality evidence; and high-dose versus standard-dose: one study; 855 participants; RR 1.71, 95% CI 0.51 to 5.81; low-quality evidence).Six studies reported the number of platelet transfusions; we were unable to perform a meta-analysis. Two studies (959 participants) out of three (1070 participants) found that a low-dose transfusion strategy led to more transfusion episodes than a standard-dose. One study (849 participants) found that a low-dose transfusion strategy led to more transfusion episodes than a high-dose strategy. One study (855 participants) out of three (1007 participants) found no difference in the number of platelet transfusions between the high-dose and standard-dose groups.One study reported on transfusion reactions. This study's authors suggested that a high-dose platelet transfusion strategy may lead to a higher rate of transfusion-related adverse events.None of the studies reported quality-of-life.

AUTHORS' CONCLUSIONS

In haematology patients who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT, we found no evidence to suggest that a low-dose platelet transfusion policy is associated with an increased bleeding risk compared to a standard-dose or high-dose policy, or that a high-dose platelet transfusion policy is associated with a decreased risk of bleeding when compared to a standard-dose policy.A low-dose platelet transfusion strategy leads to an increased number of transfusion episodes compared to a standard-dose strategy. A high-dose platelet transfusion strategy does not decrease the number of transfusion episodes per participant compared to a standard-dose regimen, and it may increase the number of transfusion-related adverse events.Findings from this review would suggest a change from current practice, with low-dose platelet transfusions used for people receiving in-patient treatment for their haematological disorder and high-dose platelet transfusion strategies not being used routinely.

A therapeutic-only versus prophylactic platelet transfusion strategy for preventing bleeding in patients with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in thrombocytopenic patients with bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004 and updated in 2012 that addressed four separate questions: therapeutic-only versus prophylactic platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. We have now split this review into four smaller reviews looking at these questions individually; this review is the first part of the original review.

OBJECTIVES

To determine whether a therapeutic-only platelet transfusion policy (platelet transfusions given when patient bleeds) is as effective and safe as a prophylactic platelet transfusion policy (platelet transfusions given to prevent bleeding, usually when the platelet count falls below a given trigger level) in patients with haematological disorders undergoing myelosuppressive chemotherapy or stem cell transplantation.

SEARCH METHODS

We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (Cochrane Library 2015, Issue 6), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950) and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

RCTs involving transfusions of platelet concentrates prepared either from individual units of whole blood or by apheresis, and given to prevent or treat bleeding in patients with malignant haematological disorders receiving myelosuppressive chemotherapy or undergoing HSCT.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We identified seven RCTs that compared therapeutic platelet transfusions to prophylactic platelet transfusions in haematology patients undergoing myelosuppressive chemotherapy or HSCT. One trial is still ongoing, leaving six trials eligible with a total of 1195 participants. These trials were conducted between 1978 and 2013 and enrolled participants from fairly comparable patient populations. We were able to critically appraise five of these studies, which contained separate data for each arm, and were unable to perform quantitative analysis on one study that did not report the numbers of participants in each treatment arm.Overall the quality of evidence per outcome was low to moderate according to the GRADE approach. None of the included studies were at low risk of bias in every domain, and all the studies identified had some threats to validity. We deemed only one study to be at low risk of bias in all domains other than blinding.Two RCTs (801 participants) reported at least one bleeding episode within 30 days of the start of the study. We were unable to perform a meta-analysis due to considerable statistical heterogeneity between studies. The statistical heterogeneity seen may relate to the different methods used in studies for the assessment and grading of bleeding. The underlying patient diagnostic and treatment categories also appeared to have some effect on bleeding risk. Individually these studies showed a similar effect, that a therapeutic-only platelet transfusion strategy was associated with an increased risk of clinically significant bleeding compared with a prophylactic platelet transfusion policy. Number of days with a clinically significant bleeding event per participant was higher in the therapeutic-only group than in the prophylactic group (one RCT; 600 participants; mean difference 0.50, 95% confidence interval (CI) 0.10 to 0.90; moderate-quality evidence). There was insufficient evidence to determine whether there was any difference in the number of participants with severe or life-threatening bleeding between a therapeutic-only transfusion policy and a prophylactic platelet transfusion policy (two RCTs; 801 participants; risk ratio (RR) 4.91, 95% CI 0.86 to 28.12; low-quality evidence). Two RCTs (801 participants) reported time to first bleeding episode. As there was considerable heterogeneity between the studies, we were unable to perform a meta-analysis. Both studies individually found that time to first bleeding episode was shorter in the therapeutic-only group compared with the prophylactic platelet transfusion group.There was insufficient evidence to determine any difference in all-cause mortality within 30 days of the start of the study using a therapeutic-only platelet transfusion policy compared with a prophylactic platelet transfusion policy (two RCTs; 629 participants). Mortality was a rare event, and therefore larger studies would be needed to establish the effect of these alternative strategies. There was a clear reduction in the number of platelet transfusions per participant in the therapeutic-only arm (two RCTs, 991 participants; standardised mean reduction of 0.50 platelet transfusions per participant, 95% CI -0.63 to -0.37; moderate-quality evidence). None of the studies reported quality of life. There was no evidence of any difference in the frequency of adverse events, such as transfusion reactions, between a therapeutic-only and prophylactic platelet transfusion policy (two RCTs; 991 participants; RR 1.02, 95% CI 0.62 to 1.68), although the confidence intervals were wide.

AUTHORS' CONCLUSIONS

We found low- to moderate-grade evidence that a therapeutic-only platelet transfusion policy is associated with increased risk of bleeding when compared with a prophylactic platelet transfusion policy in haematology patients who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT. There is insufficient evidence to determine any difference in mortality rates and no evidence of any difference in adverse events between a therapeutic-only platelet transfusion policy and a prophylactic platelet transfusion policy. A therapeutic-only platelet transfusion policy is associated with a clear reduction in the number of platelet components administered.

Prophylactic platelet transfusions: should they be a treatment of the past?

PURPOSE OF REVIEW

For decades, prophylactic platelet transfusions have been a standard practice for treatment-related thrombocytopenia in patients with hematologic malignancies, although evidence supporting this practice was limited. Two recent randomized controlled studies were carried out to challenge this practice by comparing prophylactic to therapeutic-only platelet transfusion strategies. This review compares and contrasts the study findings to provide further insight into the study conclusions and their application to practice.

RECENT FINDINGS

Past studies exploring platelet transfusion in this patient population focused on identifying the optimal platelet threshold for transfusions and the minimum effective dose to achieve hemostasis. Balancing increased demand with limited supply has further necessitated determining if a therapeutic-only approach is as efficacious. This is especially pertinent given improved prognosis of hematologic malignancies because of novel therapies and better diagnostic technologies. Two large randomized controlled studies showed that therapeutic-only strategy reduces platelet utilization, but possibly at an increased risk of high-grade bleeding in certain patient groups.

SUMMARY

The majority of this adult patient population should continue to receive prophylactic platelet transfusions to prevent high-grade bleeding. Stable autologous stem cell transplant patients appear to be at a lower risk of thrombocytopenia-related bleeding and are candidates for therapeutic-only platelet transfusions in expert centers with careful monitoring.

Risk of bleeding and use of platelet transfusions in patients with hematologic malignancies: recurrent event analysis

A recent randomized trial (TOPPS) compared prophylactic platelet transfusions (for counts <10×10(9)/L) with a strategy of no-prophylaxis in adults with hematologic malignancies. Seventy percent of enrolled patients received an autologous hematopoietic stem cell transplant. Statistical models were developed to explore which patient factors or clinical characteristics are important prognostic factors for bleeding. These models were presented for baseline characteristics and for recurrent analysis of bleeding to assess the risks of World Health Organization grade 2-4 bleeding on any given day. Additional analyses explored the importance of fever. Treatment plan (chemotherapy/allogeneic hematopoietic stem cell transplant), female sex, and treatment arm (no-prophylaxis) were significantly associated with an increased number of days of bleeding. The number of days with a platelet count <10×109/L was significantly associated with a grade 2-4 bleed (P<0.0001). Patients with a temperature of at least 38°C had the highest hazard of a grade 2-4 bleed (hazard ratio: 1.7, 95% confidence interval: 1.3 to 2.4, compared with the risk in patients with a temperature <37.5°C). There was no evidence that minor bleeding predicted a grade 2-4 bleed. The results highlighted the limited role of correction of thrombocytopenia by platelet transfusion in reducing the risk of bleeding. Clinically stable patients undergoing autologous hematopoietic stem cell transplantation had the lowest risk of bleeding and benefited least from prophylactic platelet transfusions. Prospective studies are required to address the usefulness of risk factors to support better targeted platelet transfusions. TOPPS Controlled-Trials.com number ISRCTN08758735.

Alternative agents versus prophylactic platelet transfusion for preventing bleeding in patients with haematological disorders after chemotherapy or stem cell transplantation

This is the protocol for a review and there is no abstract. The objectives are as follows: To determine whether alternative agents (e.g. artificial platelet substitutes, platelet-poor plasma, fibrinogen, rFVIIa, thrombopoietin mimetics) are as effective and safe as the use of platelet transfusions for the prevention of bleeding (prophylactic platelet transfusion) in patients with haematological disorders who are undergoing myelosuppressive chemotherapy or stem cell transplantation. Antifibrinolytics (lysine analogues) will not be included in this review because they have been the focus of another Cochrane review (Wardrop 2013).

Platelet transfusion: a clinical practice guideline from the AABB

BACKGROUND

The AABB (formerly, the American Association of Blood Banks) developed this guideline on appropriate use of platelet transfusion in adult patients.

METHODS

These guidelines are based on a systematic review of randomized, clinical trials and observational studies (1900 to September 2014) that reported clinical outcomes on patients receiving prophylactic or therapeutic platelet transfusions. An expert panel reviewed the data and developed recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

RECOMMENDATION 1

The AABB recommends that platelets should be transfused prophylactically to reduce the risk for spontaneous bleeding in hospitalized adult patients with therapy-induced hypoproliferative thrombocytopenia. The AABB recommends transfusing hospitalized adult patients with a platelet count of 10 × 109 cells/L or less to reduce the risk for spontaneous bleeding. The AABB recommends transfusing up to a single apheresis unit or equivalent. Greater doses are not more effective, and lower doses equal to one half of a standard apheresis unit are equally effective. (Grade: strong recommendation; moderate-quality evidence).

RECOMMENDATION 2

The AABB suggests prophylactic platelet transfusion for patients having elective central venous catheter placement with a platelet count less than 20 × 109 cells/L. (Grade: weak recommendation; low-quality evidence).

RECOMMENDATION 3

The AABB suggests prophylactic platelet transfusion for patients having elective diagnostic lumbar puncture with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence).

RECOMMENDATION 4

The AABB suggests prophylactic platelet transfusion for patients having major elective nonneuraxial surgery with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence).

RECOMMENDATION 5

The AABB recommends against routine prophylactic platelet transfusion for patients who are nonthrombocytopenic and have cardiac surgery with cardiopulmonary bypass. The AABB suggests platelet transfusion for patients having bypass who exhibit perioperative bleeding with thrombocytopenia and/or evidence of platelet dysfunction. (Grade: weak recommendation; very-low-quality evidence).

RECOMMENDATION 6

The AABB cannot recommend for or against platelet transfusion for patients receiving antiplatelet therapy who have intracranial hemorrhage (traumatic or spontaneous). (Grade: uncertain recommendation; very-low-quality evidence).

Platelet transfusion goals in oncology patients

Despite the advances in platelet component preparation and transfusion support over the years, platelet products remain a limited resource due to their short (5 day) shelf life, and therefore their optimal use in the non-bleeding thrombocytopenic patient continue to draw much attention. There have been a number of national and international guidelines for platelet transfusion therapy in patients with hematologic diseases, some within the last 1-2 years that have incorporated key randomized controlled trials (RCTs) which address issues, such as the optimal platelet dose, the most appropriate threshold for prophylactic platelet transfusions, and whether prophylactic platelet transfusions are superior to therapeutic-only platelet transfusion practices for the prevention life-threatening bleeding in patients with hypoproliferative thrombocytopenia. This review highlights key RCTs and recent systematic reviews focused on optimal platelet transfusion therapy in adult and pediatric patients with hypoproliferative thrombocytopenia secondary to chemotherapy or hematopoietic stem cell transplant (HSCT), discuss how recent innovations in platelet component processing may affect transfusion efficiency, and introduce renewed concepts on adjuvant therapies to prevent bleeding in the hypoproliferative thrombocytopenic patient.

Transfusion efficacy of apheresis platelet concentrates irradiated at the day of transfusion is significantly superior compared to platelets irradiated in advance

BACKGROUND

Gamma irradiation is currently the standard care to avoid transfusion-associated graft-versus-host disease. Guidelines on gamma irradiation of blood components state that platelets (PLTs) can be irradiated at any stage in their 5-day storage and can thereafter be stored up to their normal shelf life of 5 days after collection. In this study, we explored whether the timing of irradiation has an effect on transfusion efficacy of apheresis PLT concentrates (APCs).

METHODS

Based on the 1-hour percent PLT recovery (PPR1h), transfusion efficacy of 1,000 eligible APCs transfused to 144 children were evaluated retrospectively. PPR1h was compared in transfused APCs irradiated at the day of transfusion and APCs irradiated in advance.

RESULTS

In univariate analysis, transfusion efficacy of APCs irradiated in advance was significantly lower than that of APCs irradiated at the day of transfusion (mean PPR1h 27.7 vs. 35.0%; p = 0.007). This was confirmed in multivariate analysis (p = 0.030). Compared to non-irradiated APCs, transfusion efficacy of APCs irradiated at the day of transfusion was not significantly inferior (mean difference -2.8%; 95% CI -6.1 to 0.5%; p = 0.092), but APCs irradiated in advance were clearly less efficient (mean difference -8.1%; 95% CI -12.2 to -4.0%; p < 0.001).

CONCLUSION

Our data strongly support that APCs should not be irradiated in advance, 1.e., ≥24 h before transfusion.

Different doses of prophylactic platelet transfusion for preventing bleeding in patients with haematological disorders after chemotherapy or stem cell transplantation

This is the protocol for a review and there is no abstract. The objectives are as follows: To determine whether different doses of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect their efficacy and safety in preventing bleeding in patients with haematological disorders after chemotherapy with or without stem cell transplantation.

A therapeutic-only versus prophylactic platelet transfusion strategy for preventing bleeding in patients with haematological disorders after chemotherapy or stem cell transplantation

This is the protocol for a review and there is no abstract. The objectives are as follows: To determine whether a therapeutic-only platelet transfusion policy (platelet transfusions given when patient bleeds) is as effective and safe as a prophylactic platelet transfusion policy (platelet transfusions given to prevent bleeding usually when the platelet count falls below a given trigger level) in patients with haematological disorders undergoing myelosuppressive chemotherapy or stem cell transplantation.

Comparison of different platelet count thresholds to guide administration of prophylactic platelet transfusion for preventing bleeding in patients with haematological disorders after chemotherapy or stem cell transplantation

This is the protocol for a review and there is no abstract. The objectives are as follows: To determine whether different platelet transfusion thresholds for administration of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect the efficacy and safety of prophylactic platelet transfusions in preventing bleeding in patients with haematological disorders after chemotherapy with or without stem cell transplantation.

Transfusion guidelines: when to transfuse

Transfusion of blood and blood components has been a routine practice for more than half a century. The rationale supporting this practice is that replacement of blood loss should be beneficial for the patient. This assumption has constituted the underpinning of transfusion medicine for many decades. Only over the past 20 years, we have seen a more concerted effort to answer very basic questions regarding the value of transfusion therapy. An assessment of the value of transfusion based on well-designed and appropriately powered randomized, controlled trials is the first step in optimizing transfusion practices. Systematic reviews provide the second step by building the knowledge base necessary to assess the impact of transfusion practice on patient outcomes. The third step is the development of clinical practice guidelines, and this occurs when systematic reviews are interpreted by individuals with expertise in transfusion medicine. Such guidelines are typically supported by professional organizations and/or health authorities. Implementation of clinical practice guidelines can be challenging, especially in an area as heterogeneous as transfusion medicine. However, clinical practice guidelines are necessary for the practice of evidence-based medicine, which optimizes patient care and improves patient outcomes. This review focuses on clinical practice guidelines for transfusion of three blood components: RBCs, platelets and plasma. In addition, we provide the approach used to implement clinical practice guidelines at our own institution.

Distinct differences in platelet production and function between neonates and adults: implications for platelet transfusion practice

Thrombocytopenia is a common problem among sick neonates admitted to the neonatal intensive care unit. Among neonates, preterm infants are the subgroup at highest risk for thrombocytopenia and hemorrhage, which is frequently intracranial. Although there is no evidence of a relationship between platelet (PLT) count and occurrence of major hemorrhage, preterm infants are commonly transfused prophylactically when PLT counts fall below an arbitrary limit, and this threshold is usually higher than for older infants or adults. This liberal practice has been influenced by the observation that, in vitro, neonatal PLTs are hyporeactive in response to multiple agonists. However, full-term infants exhibit normal to increased primary hemostasis due to factors in neonatal blood that enhance the PLT-vessel wall interaction. Additionally, cardiorespiratory problems are considered the main etiologic factors in the development of neonatal intraventricular hemorrhage. In this review, we will discuss the developmental differences that exist in regard to PLT production and function, as well as in primary hemostasis in preterm and term neonates, and the implications of these developmental differences to transfusion medicine. PLT transfusions are not exempt of risk, and a better understanding of the PLT function and the hemostatic profile of premature infants and their changes over time and in response to illness is the starting point to design randomized controlled trials to define optimal use of PLT transfusions in premature neonates. Without these future trials, the marked disparities in PLT transfusion practice in neonates between hospitals and countries will remain over time.

Brodde M. State of the art in platelet function testing

Platelets perform many functions in hemostasis but also in other areas of physiology and pathology. Therefore, it is obvious that many different function tests have been developed, each one conceived and standardized for a special purpose. This review will summarize the different fields in which platelet function testing is currently in use; diagnostics of patients with bleeding disorders, monitoring patients' response to anti-platelet therapy, monitoring in transfusion medicine (blood donors, platelet concentrates, and after transfusion), and monitoring in perioperative medicine to predict bleeding tendency. The second part of the review outlines different methods for platelet function testing, spanning bleeding time, and platelet counting as well as determining platelet adhesion, platelet secretion, platelet aggregation, platelet morphology, platelet signal transduction, platelet procoagulant activity, platelet apoptosis, platelet proteomics, and molecular biology.