Platelet Transfusion: A Dose-Response Study

There is no dose-response relationship between allogeneic blood transfusion and healthcare-associated infection: a retrospective cohort study

Background

The association between allogeneic blood transfusion and healthcare-associated infection (HAI) is considered dose-dependent. However, this association may be confounded by transfusion duration, as prolonged hospitalization stay increases the risk of HAI. Also, it is not clear whether specific blood products have different dose–response risks.

Methods

In this retrospective cohort study, a logistic regression was used to identify confounding factors, and the association between specific blood products and HAI were analyzed. Then Cox regression and restricted cubic spline regression was used to visualize the hazard of HAI per transfusion product.

Results

Of 215,338 inpatients observed, 4.16% were transfused with a single component blood product. With regard to these transfused patients, 480 patients (5.36%) developed a HAI during their hospitalization stay. Logistic regression showed that red blood cells (RBCs) transfusion, platelets transfusion and fresh-frozen plasmas (FFPs) transfusion were risk factors for HAI [odds ratio (OR) 1.893, 95% confidence interval (CI) 1.656–2.163; OR 8.903, 95% CI 6.646–11.926 and OR 1.494, 95% CI 1.146–1.949, respectively]. However, restricted cubic spline regression analysis showed that there was no statistically dose–response relationship between different transfusion products and the onset of HAI.

Conclusions

RBCs transfusion, platelets transfusion and FFPs transfusion were associated with HAI, but there was no dose–response relationship between them.

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.

Analysis of Donor Safety in High Yield Plateletpheresis Procedures: An Experience from Tertiary Care Hospital in South India

The apheresis platelets are the preferred blood components for the thrombocytopenic hemato-oncology patients. The one of the important factors for post transfusion increment is the dose of the platelet product infused. The minimum platelet product yield is defined but the amount of maximum possible platelets collection from a single donor is not universally defined. There is lots of apprehension in our country for apheresis procedures harvesting more than a standard unit. This retrospective observational study was conducted to determine safety of high yield plateletapheresis collection among Indian donors This retrospective observational study was conducted for a period of 15 months including all consecutive plateletapheresis procedures. The informed consent had been obtained from all donors including high yield plateletapheresis (Yield ≥ 5 × 10¹¹). The apheresis product was subjected to platelet count. The donor adverse reactions were recorded along with procedural details. Post procedure complete blood count was done for the donors who consented for post procedure blood sample draw A total 569 procedures were performed during this period including 174 high yield procedure. The 526 procedures were analyzed for adverse donor reactions. The 43 were excluded for adverse donor reaction analysis due to yield less than 3 × 10¹¹ (n = 43). The adverse reactions rate between high yield procedures (18/174, 10.34%) and normal yield (20/352, 5.68%) were not statistically different (p = 0.052). The phlebotomy related complication (3.23%) followed by citrate toxicity (2.28%) were the two most common adverse reaction observed. The adverse reactions associated with high yield plateletapheresis procedures are comparable to normal yield procedures in term of overall adverse reactions observed and post procedural platelet counts. This can be beneficial to patients by providing products of greater yield.

Post-transfusion platelet responses in critically ill cancer patients with hypoproliferative thrombocytopenia

BACKGROUND

Platelet transfusion is aimed at increasing platelet counts to prevent or treat bleeding. Critically ill cancer patients with hypoproliferative thrombocytopenia are high consumers of blood products. We herein described their post-transfusion platelet responses in the intensive care unit (ICU) and analyzed the determinants of poor post-transfusion increments.

STUDY DESIGN AND METHODS

This was a single-center 9-year (2009-2017) retrospective observational study. Patients with malignancies and presumed or proven hypoproliferative thrombocytopenia who had received at least one platelet transfusion in the ICU were included. Poor post-transfusion platelet increments were defined as body surface-adjusted corrected count increment (CCI) <7, or alternatively as weight-adjusted platelet transfusion recovery (PTR) <0.2. Patients were deemed refractory to platelet transfusions when two consecutive ABO-compatible transfusions resulted in poor platelet increments.

RESULTS

A total of 1470 platelet transfusions received by 326 patients were analyzed. Indications for platelet transfusions were distributed into prophylactic (44.5%), peri-procedural (18.1%) and therapeutic (37.4%). Regardless of indications, 54.6% and 55.4% of transfusion episodes were associated with a CCI <7 or a PTR <0.2. Factors independently associated with poor post-transfusion increments were lower body mass index, spleen enlargement, concurrent severity of clinical condition, fever ≥39°C, antibiotic therapy and increased storage duration of platelet concentrates. Eventually, 48 patients developed refractoriness to platelet transfusion, which was associated increased incidence of bleeding events.

CONCLUSION

Platelet transfusions are often associated with poor increments in critically ill cancer patients with hypoproliferative thrombocytopenia. The findings suggest amenable interventions to improve the platelet transfusion practices in this setting.

Comparison of efficacy of low and high dose prophylactic platelet transfusion therapy in thrombocytopenic haemato-oncology patients

INTRODUCTION

To determine an optimal platelet dose in thrombocytopenic patients is important for their judicious use. Transfusing platelets in different doses and comparing their post transfusion response can achieve this.

AIM

To compare the efficacy of low and high dose single donor apheresis platelets (SDAP) with standard dose transfusions in terms of Corrected Count Increment (CCI), Percent Platelet Recovery (PPR) and transfusion free interval.

METHOD

It was a prospective case control study done from January 2016 to April 2017. Twenty-eight hemato-oncology patients with CCI ≥5000 at 20-24 hours after standard dose (3 × 10¹¹/unit), received low dose (1.5 × 10¹¹ platelets/unit) and high dose (>4 × 10¹¹ platelets/unit) SDAP. CCI and PPR were calculated after 20 to 24 hours of transfusion. Transfusion free interval and bleeding episodes were also noted. Grading was done according to WHO bleeding scale.

RESULT

There was no statistical difference in CCI and PPR when standard dose was compared with low dose (CCI: p = 0.92, PPR: p = 0.89). When standard and high dose was compared, standard dose gave better results than the high dose in terms of CCI (p = 0.006) and PPR (p = 0.008) although the post transfusion increments were comparable (p = 0.938). High dose gave better (p = 0.005) platelet count increments than low dose but CCI (p = 0.04) and PPR (p = 0.05) was significantly less than the low dose. The difference in transfusion free intervals after three doses was not significant. Donor exposure to the patients was significantly (p = 0.000) reduced to 17.5%.

CONCLUSION

Possibility of low dose as an alternative to standard dose can be considered in view of comparable platelet response indicators and significantly reduced donor exposure.

Thrombocytopenia and Critical Care Medicine

Platelet transfusions play an important role in the treatment of critically ill patients. Like any blood component, however, there are various aspects of platelet transfusion therapy that need be considered by the intensivist. These include the proper dose and type of platelet component to infuse, as well as the route and method of administration. Methods to reduce the volume of the transfused platelets, for example, must ensure that the infused platelets will be functional and viable, posttransfusion. Treatment and diagnosis of the HLA alloimmunized recipient can pose a serious challenge to the clinician and an obstacle to adequate platelet therapy. An ICU patient for whom an adequate posttransfusion platelet increment cannot be achieved is at great risk of suffering a fatal hemorrhage. The ICU physician should be aware of the techniques used in modern transfusion practice to avoid having to deal with this complication. Adverse reactions to platelet transfusion include not only serologic ones, but those related to febrile and allergic complications, as well as infectious complications. The latter group includes diseases caused by infection with cytomegalovirus, bacteria, and a cadre of viruses including HIV and hepatitis. The clinical approach to thrombocytopenia in the ICU will be covered in some detail in an effort to review many of the conditions associated with recipient thrombocytopenia, including ITP, TTP, dilutional thrombocytopenia, DIC, surgery, HELLP syndrome, and drug-induced thrombocytopenia. Unfortunately the treatment approaches traditionally used are not always derived from evidence-based studies. This review covers many of these topics in an attempt to help physicians become better able to manage thrombocytopenia in the ICU and thus provide the best transfusion therapy for their patients.

Current Status of Platelet Transfusion in Pediatric Patients

Outside the neonatal period, most platelets that are transfused to pediatric patients are given to those who are thrombocytopenic secondary to malignancy and associated therapy and/or hematopoietic progenitor cell transplant, or to those with significant bleeding associated with surgery, especially cardiac surgery. Indications for platelet transfusion, doses, and other practices for children largely mimic adult platelet transfusion protocols because there are few pediatric-specific studies in this area. Pediatric platelet transfusion practices would benefit from focused pediatric research. The appropriate indications and doses for platelet transfusions in oncology, hematopoietic progenitor cell transplant, and cardiac surgery patients need to be determined.

Cryopreserved platelet concentrate transfusions in 43 dogs: a retrospective study (2007-2013)

OBJECTIVE

To clinically characterize a group of thrombocytopenic dogs that received cryopreserved platelet concentrate (cPC) transfusion, assess efficacy of cPC treatment in improving patient outcome, and compare treated dogs to a control population of thrombocytopenic dogs that did not receive cPC transfusions.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

Eighty-six client-owned dogs (43 in treatment group, 43 in control group).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Medical records of thrombocytopenic dogs that received cPC transfusions and those of thrombocytopenic dogs that did not receive cPC (control population) from January 2007 through March 2013 were reviewed. Dogs receiving cPC were statistically more likely than controls to have a platelet trigger for cPC transfusion (P = 0.01), lower platelet count (P = 0.009) and hematocrit at presentation (P = 0.001), and lower hematocrit after cPC (P = 0.02). Although there was a statistically significant increase in platelet count from pre- to post-cPC transfusion (P = 0.002), cPC was not found to be effective in improving clinical bleeding or increasing survival compared to the control group. No other characteristics were statistically different between groups. No dogs receiving cPC had an acute transfusion reaction during hospitalization.

CONCLUSIONS

In the population described in this study, cPC was not found to increase survival, but was well tolerated. Controlled, prospective studies are necessary to determine indications for and efficacy of cPC transfusions.

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.

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.

Platelet function recovery following exposure to triple anti-platelet inhibitors using an in vitro transfusion model

INTRODUCTION

Dual anti-platelet therapy (DAPT) with aspirin and a P2Y12 antagonist is standard of care to reduce risk of thrombosis, but does not directly target thrombin-dependent platelet activation. Therefore, PAR-1 antagonist addition to DAPT (i.e., triple anti-platelet therapy; TAPT) may improve the efficacy of treatment, though at the expense of an increase in bleeding risk. Using an in vitro transfusion model, we evaluated if platelet function loss associated with TAPT can be remedied by the addition of drug-naïve platelets.

METHODS

To mimic TAPT, platelet-rich plasma (PRP) prepared from consented DAPT patients (DPRP) was incubated with a vorapaxar at therapeutic plasma levels (TPRP). To simulate platelet transfusions, TPRP was mixed with increasing proportions of drug-naïve PRP (NPRP). Platelet function recovery was assessed by light transmission aggregometry (LTA), aggregate morphology, and P-selectin expression.

RESULTS

LTA results demonstrated that 20% NPRP was required to restore the ADP aggregation response in TPRP to the response observed in DPRP and 40% NPRP recovered aggregation to >65%. Higher NPRP fractions (60%) were required to restore the platelet reactivity using TRAP-6 (SFLLRN) or arachidonic acid (AA). PAR-4 aggregation was unaffected by platelet antagonists. A decrease in single, free platelets and incorporation of mepacrine-labeled naïve platelets into aggregates occurred with increasing NPRP portions. Upon agonist activation, the surface density and percent of P-selectin positive platelets increased linearly upon addition of NPRP.

CONCLUSION

This in vitro model demonstrated that administration of drug-naïve platelets can be a useful strategy for reversing overall platelet inhibition observed with TAPT.

Clinical and quality evaluation of apheresis vs random-donor platelet concentrates stored for 7 days

BACKGROUND AND OBJECTIVES

The clinical efficacy of different types of platelets remains under debate. We conducted a pilot study to prospectively evaluate the impact of subsequent storage on the in vitro quality and post-transfusion outcome of apheresis prepared platelets (APCs) vs random donor platelets (RDPs).

MATERIALS AND METHODS

We studied 30 units of APCs, and 30 units of RDPs. We performed assays on days 1, 3, 5 and 7, evaluating ADP aggregation, platelet count and pH. Fifteen thrombocytopenic patients with haematologic conditions were evaluated. Each patient received prophylactic transfusions of both components, and their post-transfusion platelet increments were compared. Twenty-five transfusions were apheresis prepared, and 35 transfusions were received as RDPs. None of the RDPs were leukoreduced.

RESULTS

The median platelet counts for APCs on days 1, 3, 5 and 7 were; 2070, 1990, 1680 and 1240 × 10(3)  µL(-1) , respectively, and were; 1290, 850, 499 and 284 × 10(3)  µL(-1) , respectively for RDPs. The pH of all units was more than 6·2. Both groups demonstrated a significant decrease of ADP aggregation after 3 days of storage (P < 0·05). However, APCs provided satisfactory increments for 90·9% of transfusions. On the sixth and seventh days of storage, APCs provided significantly higher platelet increments (18·7 × 10(3)  µL(-1) ) compared with RDPs (3·20 × 10(3)  µL(-1) ) (P < 0·05). Significantly longer transfusion intervals were also achieved with APCs (P < 0·05).

CONCLUSION

Although other variables may have confounded the results, subsequent storage of APCs appeared to provide higher increments with longer intervals of transfusion compared with RDPs. Future prospective studies are needed, adjusting for other possible confounding variables.

Use of fresh platelet concentrate or lyophilized platelets in thrombocytopenic dogs with clinical signs of hemorrhage: a preliminary trial in 37 dogs

OBJECTIVE

To examine the safety and feasibility of using lyophilized platelets (LYO) and fresh platelet concentrate (FRESH) in bleeding thrombocytopenic dogs.

DESIGN

Preliminary prospective randomized clinical trial.

SETTING

Two private referral centers and 3 university teaching hospitals.

ANIMALS

Thirty-seven dogs with a complaint of hemorrhage associated with thrombocytopenia (platelet count <70 × 10(9) /L [70,000/μL], a hematocrit >15%, and that had received neither vincristine nor platelet-containing transfusions within 72 h of enrollment were studied.

INTERVENTIONS

Animals were randomized to receive LYO or FRESH, dosed according to weight. Physical examination, complete blood counts, and coagulation testing (prothrombin time and activated partial thromboplastin time) were performed at enrollment. Physical examinations were also performed immediately post transfusion, and at 1 and 24 h after transfusion. Complete blood counts were repeated immediately post transfusion and at 24 h. Collected data included bleeding score (BLS), response to transfusion, adverse reactions, hospitalization time, need for additional transfusions, survival to discharge, and 28-d survival.

MEASUREMENTS AND MAIN RESULTS

Twenty-two dogs received LYO and 15 received FRESH. There was no difference between groups in age, weight, BLS, platelet count, white blood cell count, hematocrit, or presence of melena. There was no difference between groups in transfusion reaction rates, the need for additional transfusions, 24-h BLS, hospitalization time, survival to discharge, or 28-d survival.

CONCLUSIONS

Transfusion of LYO was feasible and associated with a low transfusion reaction rate in this limited study of thrombocytopenic canine patients presenting with mild-to-severe hemorrhage. LYO were easy to use and provided storage advantages over FRESH. Further study of this product, including examination of efficacy and platelet life span, is warranted.

Prophylactic platelet transfusion for prevention of bleeding in patients with haematological disorders after chemotherapy and 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.

OBJECTIVES

To determine the most effective use of platelet transfusion for the prevention of bleeding in patients with haematological disorders undergoing chemotherapy or stem cell transplantation.

SEARCH METHODS

This is an update of a Cochrane review first published in 2004. We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL Issue 4, 2011), MEDLINE (1950 to Nov 2011), EMBASE (1980 to Nov 2011) and CINAHL (1982 to Nov 2011), using adaptations of the Cochrane RCT search filter, the UKBTS/SRI Transfusion Evidence Library, and ongoing trial databases to 10 November 2011.

SELECTION CRITERIA

RCTs involving transfusions of platelet concentrates, prepared either from individual units of whole blood or by apheresis, and given to prevent bleeding in patients with haematological disorders. Four different types of prophylactic platelet transfusion trial were included.

DATA COLLECTION AND ANALYSIS

In the original review one author initially screened all electronically derived citations and abstracts of papers, identified by the review search strategy, for relevancy. Two authors performed this task in the updated review. Two authors independently assessed the full text of all potentially relevant trials for eligibility. Two authors completed data extraction independently. We requested missing data from the original investigators as appropriate.

MAIN RESULTS

There were 18 trials that were eligible for inclusion, five of these were still ongoing.Thirteen completed published trials (2331 participants) were included for analysis in the review. The original review contained nine trials (718 participants). This updated review includes six new trials (1818 participants).Two trials (205 participants) in the original review are now excluded because fewer than 80% of participants had a haematological disorder.The four different types of prophylactic platelet transfusion trial, that were the focus of this review, were included within these thirteen trials.Three trials compared prophylactic platelet transfusions versus therapeutic-only platelet transfusions. There was no statistical difference between the number of participants with clinically significant bleeding in the therapeutic and prophylactic arms but the confidence interval was wide (RR 1.66; 95% CI 0.9 to 3.04).The time taken for a clinically significant bleed to occur was longer in the prophylactic platelet transfusion arm. There was a clear reduction in platelet transfusion usage in the therapeutic arm. There was no statistical difference between the number of participants in the therapeutic and prophylactic arms with platelet refractoriness, the only adverse event reported.Three trials compared different platelet count thresholds to trigger administration of prophylactic platelet transfusions. No statistical difference was seen in the number of participants with clinically significant bleeding (RR 1.35; 95% CI 0.95 to 1.9), however, this type of bleeding occurred on fewer days in the group of patients transfused at a higher platelet count threshold (RR 1.72; 95% CI 1.33 to 2.22).The lack of a difference seen for the number of participants with clinically significant bleeding may be due to the studies, in combination, having insufficient power to demonstrate a difference, or due to masking of the effect by a higher number of protocol violations in the groups of patients with a lower platelet count threshold. Using a lower platelet count threshold led to a significant reduction in the number of platelet transfusions used. There were no statistical differences in the number of adverse events reported between the two groups.Six trials compared different doses of prophylactic platelet transfusions. There was no evidence to suggest that using a lower platelet transfusion dose increased: the number of participants with clinically significant (WHO grade 2 or above) (RR 1.02; 95% CI 0.93 to 1.11), or life-threatening (WHO grade 4) bleeding (RR 1.87; 95% CI 0.86 to 4.08). A higher platelet transfusion dose led to a reduction in the number of platelet transfusion episodes, but an increase in total platelet utilisation. Only one adverse event, wheezing after transfusion, had a significantly higher incidence when standard and high dose transfusions were compared but this difference was not seen when low dose and high dose transfusions were compared. It is therefore likely to be a type I error (false positive).One small trial compared prophylactic platelet transfusions versus platelet-poor plasma. The risk of a significant bleed was decreased in the prophylactic platelet transfusion arm (RR 0.47; 95% CI 0.23 to 0.95) and this was statistically significant.All studies had threats to validity; the majority of these were due to methodology of the studies not being described in adequate detail.Although it was not the main focus of the review, it was interesting to note that in one of the pre-specified sub-group analyses (treatment type) two studies showed that patients receiving an autologous transplant have a lower risk of bleeding than patients receiving intensive chemotherapy or an allogeneic transplant (RR 0.73, 95% CI 0.65 to 0.82).

AUTHORS' CONCLUSIONS

These conclusions refer to the four different types of platelet transfusion trial separately. Firstly, there is no evidence that a prophylactic platelet transfusion policy prevents bleeding. Two large trials comparing a therapeutic versus prophylactic platelet transfusion strategy, that have not yet been published, should provide important new data on this comparison. Secondly, there is no evidence, at the moment, to suggest a change from the current practice of using a platelet count of 10 x 10(9)/L. However, the evidence for a platelet count threshold of 10 x 10(9)/L being equivalent to 20 x 10(9)/L is not as definitive as it would first appear and further research is required. Thirdly, platelet dose does not affect the number of patients with significant bleeding, but whether it affects number of days each patient bleeds for is as yet undetermined. There is no evidence that platelet dose affects the incidence of WHO grade 4 bleeding.Prophylactic platelet transfusions were more effective than platelet-poor plasma at preventing bleeding.

New thoughts on the correct dosing of prophylactic platelet transfusions to prevent bleeding

PURPOSE OF REVIEW

Recent studies have evaluated the effects of platelet dose on hemostasis.

RECENT FINDINGS

As long as a critical level of 5000  platelets/μl is maintained, platelet counts do not affect bleeding. The risk of WHO grade 2 or greater bleeding was 25% on days with morning platelet counts of less than 5000/μl and was 17% at platelet counts between 6000 and 80 000/μl (P < 0.001). Therefore, it is not surprising that platelet doses of half to twice the usual dose of 2.2 × 10(11)  platelets/transfusion/body surface area (BSA) do not affect any bleeding grade. However, the risk of grade 2 or greater bleeding is higher in patients receiving an allogeneic hematopoietic stem cell transplant (HSCT, 79%) versus those receiving chemotherapy for hematologic malignancies (73%) or those receiving an autologous HSCT (57%) (P < 0.001 for the latter versus the first two groups). In contrast, in children under 18, the risk of bleeding was higher in all treatment groups than in adults, particularly for children receiving autologous HSCT (93 to 83% based on increasing patient age). However, for none of these treatment categories did platelet dose affect bleeding risk.

SUMMARY

Platelet doses in ranges between half to twice the usual dose of 2.2 × 10(11)  platelets/transfusion/BSA have no affect on WHO bleeding grades.

A comprehensive program to minimize platelet outdating

BACKGROUND

Platelet (PLT) transfusions are essential for patients who are bleeding or have an increased risk of bleeding due to a decreased number or abnormal function of circulating PLTs. A shelf life of 5 days for PLT products presents an inventory management challenge. In 2006, greater than 10% of apheresis PLTs made in the United States outdated. It is imperative to have a sufficient number of products for patients requiring transfusion, but outdating PLTs is a financial burden and a waste of a resource.

STUDY DESIGN AND METHODS

We present the approach used in our institution to anticipate inventory needs based on current patient census and usage. Strategies to predict usage and to identify changes in anticipated usage are examined. Annual outdating is reviewed for a 10-year period from 2000 through 2009.

RESULTS

From January 1, 2000, through December 2009, there were 128,207 PLT transfusions given to 15,265 patients. The methods used to anticipate usage and adjust inventory resulted in an annual outdate rate of approximately 1% for the 10-year period reviewed. In addition we have not faced situations where inventory was inadequate to meet the needs of the patients requiring transfusions.

CONCLUSION

We have identified three elements of our transfusion service that can minimize outdate: a knowledgeable proactive staff dedicated to PLT management, a comprehensive computer-based transfusion history for each patient, and a strong two-way relationship with the primary product supplier. Through our comprehensive program, based on the principles of providing optimal patient care, we have minimized PLT outdating for more than 10 years.

Platelet dose for prophylactic platelet transfusions

Although guidelines exist to deal with some aspects of platelet transfusion practice, many important clinical issues have not been addressed in large randomized controlled trials (RCTs). Slichter et al. conducted a RCT of prophylactic platelet transfusions to determine the effects of the dose of platelets on clinical signs of bleeding, the use of platelet and red cell transfusions, changes in the recipient's post-transfusion platelet count, days to next transfusion and adverse events (Effects of Prophylactic Platelet Dose on Transfusion Outcomes [PLADO] trial). The primary end point of the study (i.e., the percentage of patients in each group with at least one episode of bleeding of grade 2 or higher according to the WHO criteria) was not significantly different (71, 69 and 70% of patients in the low-, medium- and high-dose group, respectively). According to these data, one can conclude that the dose of platelets transfused has no significant effect on the incidence of bleeding in patients with hypoproliferative thrombocytopenia and platelet counts no greater than 10 × 10⁹/l.

Current practice and future directions for optimization of platelet transfusions in patients with severe therapy-induced cytopenia

Platelet transfusions are mainly used for patients with thrombocytopenia due to bone marrow failure, especially cancer patients developing severe chemotherapy-induced thrombocytopenia (e.g. patients with acute leukemia or other hematologic malignancies). A prophylactic transfusion strategy is now generally accepted in developed countries. Some clinical data, however, support the use of a therapeutic transfusion strategy at least for certain subsets of these patients. Several methodological approaches can then be used to evaluate the outcome of platelet transfusions, including peripheral blood platelet increments and bleeding assessments. Several factors will influence the efficiency of platelet transfusions; fever and ongoing hemorrhage are among the most important patient-dependent factors, but the number and quality of the transfused platelets are also important. The quality of transfused platelets can be evaluated by analyzing platelet activation, metabolism or senescence/apoptosis. Only evaluation of metabolism is included in international guidelines, but high-throughput methods for evaluation of activation and senescence/apoptosis are available and should be incorporated into routine clinical practice if future studies demonstrate that they reflect clinically relevant platelet characteristics. Finally, platelet transfusions have additional biological effects that may cause immunomodulation or altered angioregulation; at present it is not known whether these effects will influence the long-time prognosis of cancer patients. Thus, several questions with regard to the optimal use of platelet transfusions in cancer patients still need to be answered.

Platelet transfusions: impact on hemostasis, thrombosis, inflammation and clinical outcomes

Platelet transfusion is one of the most crucial therapeutic approaches in Medicine. However, severe and fatal adverse reactions may develop. In addition to their important function in hemostasis, platelets' role in inflammation has become more evident. Recently, platelets are also recognized as the main source of circulating soluble CD40 ligand (sCD40L, (CD154)), which plays significant roles in hemostasis, platelet activation, clot stability, interactions with other cells, and upregulation of different mediators. In this review, we will briefly highlight the importance of platelet transfusion, its role in inflammatory and thrombotic transfusion reactions, and visit the most recent findings on sCD40L.

A systematic assessment of the quality of reporting for platelet transfusion studies

BACKGROUND

As evidence-based medicine assumes increasing importance, there is a need for high-quality reporting of clinical studies. A recent review of clinical platelet (PLT) studies indicated variability in reporting. We undertook a critical analysis of PLT transfusion studies to determine the quality of reporting.

STUDY DESIGN AND METHODS

A systematic MEDLINE search for clinical studies of PLT transfusion was performed to identify articles. Relevant observational studies (OBS) were critiqued using the STROBE checklist and randomized controlled clinical trials (RCTs) using the CONSORT checklist. Studies were further evaluated with a PLT-specific checklist developed by the authors. Observations were analyzed descriptively and using Pareto analysis.

RESULTS

A total of 772 articles were identified by the search. Eighty-six articles (23 RCTs and 63 OBS) met eligibility criteria. All RCTs, and a similar number of OBS (24), were randomly selected for analysis. Studies reported the scientific background and rationale, key results, and outcomes. OBS frequently did not consider bias and confounders. RCTs frequently did not explain bias, interim analyses, stopping rules, success of blinding, or weaknesses of multiple analyses. The PLT-specific critique found many studies adequately reported basics of the PLT product, PLT increment, and transfusion reactions. Studies frequently failed to report specific details of PLT compatibility, details of product preparation, and use of other blood products.

CONCLUSION

Recently published articles of clinical PLT transfusion share common strengths and weaknesses. The quality of reporting may be improved by providing guidelines to authors and journal editors that list the essential elements of a well-reported clinical study of PLT transfusion.

Dose of prophylactic platelet transfusions and prevention of hemorrhage

BACKGROUND

We conducted a trial of prophylactic platelet transfusions to evaluate the effect of platelet dose on bleeding in patients with hypoproliferative thrombocytopenia.

METHODS

We randomly assigned hospitalized patients undergoing hematopoietic stem-cell transplantation or chemotherapy for hematologic cancers or solid tumors to receive prophylactic platelet transfusions at a low dose, a medium dose, or a high dose (1.1x10(11), 2.2x10(11), or 4.4x10(11) platelets per square meter of body-surface area, respectively), when morning platelet counts were 10,000 per cubic millimeter or lower. Clinical signs of bleeding were assessed daily. The primary end point was bleeding of grade 2 or higher (as defined on the basis of World Health Organization criteria).

RESULTS

In the 1272 patients who received at least one platelet transfusion, the primary end point was observed in 71%, 69%, and 70% of the patients in the low-dose group, the medium-dose group, and the high-dose group, respectively (differences were not significant). The incidences of higher grades of bleeding, and other adverse events, were similar among the three groups. The median number of platelets transfused was significantly lower in the low-dose group (9.25x10(11)) than in the medium-dose group (11.25x10(11)) or the high-dose group (19.63x10(11)) (P=0.002 for low vs. medium, P<0.001 for high vs. low and high vs. medium), but the median number of platelet transfusions given was significantly higher in the low-dose group (five, vs. three in the medium-dose and three in the high-dose group; P<0.001 for low vs. medium and low vs. high). Bleeding occurred on 25% of the study days on which morning platelet counts were 5000 per cubic millimeter or lower, as compared with 17% of study days on which platelet counts were 6000 to 80,000 per cubic millimeter (P<0.001).

CONCLUSIONS

Low doses of platelets administered as a prophylactic transfusion led to a decreased number of platelets transfused per patient but an increased number of transfusions given. At doses between 1.1x10(11) and 4.4x10(11) platelets per square meter, the number of platelets in the prophylactic transfusion had no effect on the incidence of bleeding. (ClinicalTrials.gov number, NCT00128713.)

Gastrointestinal bleeding in the cancer patient

Gastrointestinal bleeding is a common occurrence in patients with cancer and is a frequent indicator of a gastrointestinal malignancy. Rapid evaluation and treatment is key for the hemodynamically unstable patient. Endoscopy remains the cornerstone of diagnosis and management for cancer patients with gastrointestinal bleeding. The emergency physician should also be aware of other diagnostic and treatment modalities that may be needed to take care of these patients.

Development of fibrinogen gamma-chain peptide-coated, adenosine diphosphate-encapsulated liposomes as a synthetic platelet substitute

BACKGROUND

The dodecapeptide HHLGGAKQAGDV (H12), corresponding to the fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411), is a specific binding site of the ligand for platelet GPIIb/IIIa complex. We have evaluated H12-coated nanoparticles (polymerized albumin or liposome) as platelet function-supporting synthetic products.

OBJECTIVES

To strengthen the hemostatic ability of H12-coated particles as a platelet substitute, we exploited installation of a drug delivery function by encapsulating adenosine diphosphate (ADP) into liposomes [H12-(ADP)-liposomes].

METHODS AND RESULTS

Via selective interaction with activated platelets through GPIIb/IIIa, H12-(ADP)-liposomes were capable of augmenting agonist-induced platelet aggregation by releasing ADP in an aggregation-dependent manner. When intravenously injected into rats, liposomes were readily targeted to sites of vascular injury as analyzed on computed tomography. In fact, comparable to fresh platelets, liposomes exhibited considerable hemostatic ability for correcting prolonged bleeding time in a busulphan-induced thrombocytopenic rabbit model. In addition, the liposomes showed no activating or aggregating effects on circulating platelets in normal rabbits.

CONCLUSION

H12-(ADP)-liposome may thus offer a promising platelet substitute, being made with only synthetic materials and exerting hemostatic functions in vivo via reinforcement of primary thrombus formation by residual platelets in thrombocytopenia at sites of vascular injury, but not in circulation.

A randomized controlled trial comparing standard- and low-dose strategies for transfusion of platelets (SToP) to patients with thrombocytopenia

A noninferiority study was performed comparing low-dose and standard-dose prophylactic platelet transfusions. A double-blind randomized controlled trial (RCT) was performed in 6 sites in 3 countries. Thrombocytopenic adults requiring prophylactic platelet transfusion were randomly allocated to standard-dose (300-600 × 109 platelets/product) or low-dose (150- < 300 × 109 platelets/product) platelets. The primary outcome (World Health Organization [WHO] bleeding ≥ grade 2) was assessed daily through clinical examination, patient interview, and chart review. A WHO grade was assigned through adjudication. The Data Safety Monitoring Board stopped the study because the difference in the grade 4 bleeding reached the prespecified threshold of 5%. At this time, 129 patients had been randomized and 119 patients were included in the analysis (58 low dose; 61 standard dose). Three patients in the low-dose arm (5.2%) had grade 4 bleeds compared with none in the standard-dose arm. WHO bleeding grade 2 or higher was 49.2% (30/61) in the standard-dose arm and 51.7% (30/58) in the low-dose group (relative risk [RR], 1.052; 95% confidence interval [CI], 0.737-1.502). A higher rate of grade 4 bleeding in patients receiving low-dose prophylactic platelet transfusions resulted in this RCT being stopped. Whether this finding was due to chance or represents a real difference requires further investigation. These clinical studies are registered on http://www.clinicaltrials.gov as NCT00420914.

Consensus and controversies in platelet transfusion: trigger for indication, and platelet dose

Platelet transfusion is about to commemorate its 50th year since its introduction in therapeutics. It is then surprising to see, that in spite of reaching this respectful age, we have not been able to definitely establish all the aspects related to its clinical use. Some of these facets are platelet transfusion threshold and the platelet dose to administer. Historically, two different transfusion triggers have been used for prophylactic and therapeutic platelet transfusions. For prophylactic platelet transfusion an increasing body of evidences suggests that a transfusion trigger of 10 x 10(9) per liter is appropriate for most clinical settings. In contrast, evidence for supporting a certain therapeutic transfusion trigger is lacking. Nevertheless, there is consensus that the platelet count should not be allowed to fall below 50 x 10(9) per liter in patients with acute bleeding. Another important aspect still pending of clear definition is the issue of the platelet dose to be transfused. It has been addressed by some small studies but a definite answer to this important clinical issue is, at least so far, still pending. The results of two ongoing trials, one sponsored by NIH through the Clinical Trials Network in Transfusion Medicine and Hemostasis and the other promoted by the BEST Collaborative Group are expected to help us to clearly defining the more effective and efficient way to transfuse platelet concentrates.

Therapeutic efficacy of different types of platelet concentrates in thrombocytopenic patients

BACKGROUND

Platelet Rich Plasma-Platelet concentrate (PRP-PC), Buffy Coat poor-platelet concentrate (BCPC), and Apheresis - PC were prepared and their therapeutic efficacy were assessed in thrombocytopenic patients.

STUDY DESIGN AND METHODS

PRP-PC and BC-PC were prepared from whole blood and Apheresis-PC by automated cell separator. The post transfusion efficacy of transfused platelets was assessed at 1 hour and 20 hours by corrected count increment (CCI) and percentage recovery (PR).

RESULTS

A total of 60 patients' (20 each for PRP-PC, BC-PC and Apheresis-PC) were enrolled in this study. Forty one patients received therapeutic and nineteen received prophylactic transfusion support. Patients with aplastic anemia 43% (25/60) and acute leukemia 38% (23/60) formed a majority of study population. Platelet dosage of patients' received PRP-PC, BC-PC and apheresis-PC were 2.4±0.82 × 1011 (mean±SD), 2.2±0.83 × 1011 (mean±SD) and 4.14±1.82 × 1011 (mean±SD) and ranged from 1.16-4.11 × 1011, 1.04-4.20 × 1011 and 1.22-8.90 × 1011 respectively. There was significantly increase in inter-transfusion interval with Apheresis-PC than with PRP-PC and BC-PC recipients [(Mean±S.D.), 4.7±1.33 days Vs 2.7±0.82 days Vs 2.5±0.7 days respectively] (p < 0.05).

CONCLUSIONS

Patients transfused with apheresis-PC had received higher platelet dosage than PRP-PC and BC-PC and this difference was statistically significant (p < 0.001). The post transfusion platelet counts and increments at 1 hour and 20 hours were significantly higher with apheresis-PC than PRP-PC and BC-PC (p < 0.001). However, the corrected count increment (CCI) and percentage recovery (PR) in all three groups were comparable. There was significantly increase in inter-transfusion interval with apheresis-PC than PRPPC and BC-PC (p < 0.05).

New Strategies for the Optimal Use of Platelet Transfusions

Patients with severe thrombocytopenia are presumed to be at increased risk for bleeding, and consequently it has been standard practice for the past four decades to give allogeneic platelet transfusions to severely thrombocytopenic patients as supportive care. Platelet transfusions may be given either prophylactically to reduce the risk of bleeding, in the absence of clinical hemorrhage (prophylactic transfusions), or to control active bleeding when present (therapeutic transfusions). While no one would argue with the need for platelet transfusions in the face of severe bleeding, important questions remain about what constitutes clinically significant bleeding and whether a strategy of prophylactic platelet transfusions is effective in reducing the risk of bleeding in clinically stable patients. It is now uncommon for patients undergoing intensive chemotherapy or bone marrow transplantation to die of hemorrhage, but it is open to debate as to what degree platelet transfusions have been responsible for this change in outcome, given the many other advances in other aspects of supportive care.

If a prophylactic strategy is followed, the optimal transfusion trigger or quantity of platelets to be transfused prophylactically per transfusion episode needs to be addressed in adequately powered clinical trials, but these remain highly controversial issues. This is because, until recently, there have been few high-quality, prospective, randomized clinical trial (RCT) data for evaluating the relative effects of different platelet transfusion regimens or platelet doses on clinical outcomes. Moreover, most of these RCTs have not used bleeding as the primary outcome measure. Two such studies on platelet dose have now been undertaken, the PLADO (Prophylactic PLAtelet DOse) and the SToP (Strategies for the Transfusion of Platelets) trials. Data from these RCTs are not contained in this overview, as these data have not yet been completely analyzed or submitted for peer review publication.

In addition to the above, several recent observational studies have raised the possibility that there is not a clear association between the occurrence of a major clinical bleeding episode and the platelet count in thrombocytopenic patients. Such findings have led to the questioning of the efficacy of prophylactic platelet transfusions in all clinically stable patients, and whether a policy of therapeutic transfusions used only when patients have clinical bleeding might be as effective and safe for selected patients. At least two RCTs evaluating the relative value of prophylactic versus therapeutic platelet transfusions have been initiated in thrombocytopenic patients with hematological malignancies. One such study, known as the TOPPS (Trial of Prophylactic Platelets Study) study, is currently underway in the U.K.

Platelet transfusions

Ever since platelet transfusions were shown to reduce mortality from haemorrhage in patients with acute leukaemia in the 1950s, the use of this therapy has steadily grown to become an essential part of the treatment of cancer, haematological malignancies, marrow failure, and haematopoietic stem cell transplantation. Today, more than 1.5 million platelet products are transfused in the USA each year, 2.9 million products in Europe. However, platelet transfusion can transmit infections and trigger serious immune reactions and they can be rendered ineffective by alloimmunisation. There are several types of platelet components and all can be modified to reduce the chances of many of the complications of platelet transfusion. Transfusion practices, including indications for transfusion, dose of platelets transfused, and methods of treating alloimmunised recipients vary between countries, and even within countries. We review commonly used platelet components, product modifications, transfusion practices, and adverse consequences of platelet transfusions.

Platelet Transfusion Therapy

This article provides guidelines for the appropriate use of platelet transfusions to reduce unnecessary transfusions, thereby avoiding transfusion-related risks to the patients and the costs of platelet therapy. Platelet products available for transfusion are whole blood derived platelet concentrates and apheresis platelets. Leukoreduced platelets can be used to reduce platelet alloimmunization, cytomegalovirus transmission, and febrile transfusion reactions, while gamma irradiation prevents transfusion-associated graftversus-host disease. Other topics discussed are the expected response to transfused platelets and reasons for poor responses related to alloimmunization, underlying disease state, clinical conditions, and drugs. Appropriate transfusion guidelines based on pretransfusion platelet count, platelet dose, and whether the transfusion is prophylactic or therapeutic are outlined. Identification, prevention, and management of adverse consequences of platelet transfusions and platelet refractoriness are discussed.

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.

Facteurs influençant le rendement transfusionnel plaquettaire « une interdépendance entre le patient et le produit »

A great variety of patient- and product-related factors influence the outcome of platelet transfusions. The patient-related factors are numerous, either physical factors as weight and height, or related to pathological being as splenomegaly, fever, infection, disseminated intravascular coagulation, previous HLA allo-immunization, or related to the treatment, as amphotericin. Major platelet factors that are associated with impaired responses are giving a decreased dose of platelets, ABO incompatible products, and platelets stored for more than 48 hours. When trying to prevent or to treat refractoriness and to finely tune platelet transfusions, all these factors have to be taken into account, and a good coordination between the blood bank and the clinician team is essential.