Search

PURPOSE Ado-trastuzumab emtansine (T-DM1) treatment results in grade 3-4 thrombocytopenia in 8%-13% of patients. Prior in vitro studies reported T-DM1 inhibition of megakaryocyte maturation as the cause of decreased platelet production. The current observational study was initiated to evaluate causes of thrombocytopenia in patients with metastatic breast cancer. MATERIALS AND METHODS Patients with human epidermal growth factor receptor 2–positive metastatic breast cancer (N = 11) were enrolled in this postmarket safety study. 111-Indium- radiolabeled autologous platelet recoveries and survivals as well as serial platelet counts, bleeding time assays, and platelet aggregation responses to a wide range of agonists were performed at baseline (BL) and during two consecutive cycles of the drug (3.6 mg/kg IV once every 3 weeks). RESULTS Platelet nadirs occurred earlier in cycle 2 than in cycle 1. Average nadir counts (% BL) in cycles 1 and 2 were 116,000/µL (53% ± 6%) and 115,000/µL (51% ± 9%), respectively, with return to BL by D15 in both cycles. BL platelet survival averaged 8.8 (± 0.3) days but progressively shortened to 5.5 (± 0.5) days during cycle 1 and to 4.6 (± 0.3) days during cycle 2 ( P < .001 compared with BL for both cycles). Aggregation responses to all agonists decreased during the study, both in cycle 1 and cycle 2. CONCLUSION Following T-DM1 administration, we observed statistically significant progressive decreases in platelet survivals and decreased platelet function from BL values. In distinction to published in vitro studies, these unexpected results indicate a direct toxic effect of T-DM1 on patients' autologous circulating platelets.

Background and objectives Pathogen reduction of donor platelets with amotosalen/UVA has been shown to effectively inactivate pathogens and also contaminating white blood cells (WBCs). We wanted to determine whether WBC inactivation could also decrease alloimmune refractoriness to donor platelets. Materials and methods Platelets were prepared from a donor dog's whole blood, and the platelets were either transfused without modification [standard (STD) platelets] or treated with amotosalen/UVA under conditions modelling the amotosalen/UVA Blood System for human platelets (APR) using either 4 or 3 J/cm2 of UVA exposure. Platelets were transfused weekly from a single donor dog for 8 weeks or until the recipient dog became refractory to their donor's platelets. Antibody samples were drawn weekly and tested against the donor dog's platelets and WBCs (CD8 and B cells). Results Only 1/7 (14%) dogs that received STD platelets accepted 8 weeks of donor transfusions. Following APR 4 J/cm2 donor transfusions, 3/9 (33%) recipients accepted their donor's transfusions, but only one recipient remained antibody negative. Following APR 3 J/cm2 donor transfusions, the same dose as used for human platelet transfusions, 7/10 (70%) recipients accepted their donor's transfusions, but only two remained antibody negative. Conclusion As a very high percentage of recipient dogs (70%) accepted APR 3 J/cm2 donor transfusions, these data suggest that preventing alloimmune platelet refractoriness may be another benefit of pathogen reduction using amotosalen/UVA.

BACKGROUND Current limitations of platelet shelf life to 5 days have led to an increasingly greater demand for hemostatic agents with greater longevity. The objective of this study was to evaluate the function of a lyophilized platelet-derived hemostatic product (thrombosome [TS]) as a potential alternative to fresh platelets. METHODS Platelets were collected from whole blood from healthy donors. TSs were reconstituted with water and added to various configurations of reassembled whole blood (platelets, plasma, and RBCs); measures included rotational thromboelastometry (ROTEM), optical aggregometry, mitochondrial function, calibrated automated thrombogram, collagen adhesion under flow (shear flow assay), and flow cytometry. RESULTS In ROTEM, no differences were observed between maximum clot formation values for contact pathway activation thromboelastometry tests with TSs or platelet samples. Significantly decreased aggregation was observed in the TSs versus platelets (p

Background The purpose of our studies was to determine if fecal blood loss can provide a quantitative measure of bleeding at platelet counts of 20 000/μL or less in patients with hypoproliferative thrombocytopenia and to document the effects of different prophylactic platelet transfusion triggers on fecal blood loss. Methods and materials Patients had an aliquot of their autologous red blood cells (RBCs) labeled with 51 Cr. Following reinjection of their radiolabeled RBCs, all feces and a daily blood sample were collected to determine fecal blood loss per day. Three different studies were performed in patients with thrombocytopenia: The first was in patients with thrombocytopenia with aplastic anemia who were not receiving platelet transfusions, and the other two trials involved thrombocytopenic patients with cancer who were receiving prophylactic platelet transfusions at platelet transfusion triggers of 5000/μL, 10 000/μL, or 20 000/μL. Results In patients with thrombocytopenia not receiving platelet transfusions, fecal blood loss does not increase substantially until platelet counts are 5000/μL or less. When platelet transfusions are given prophylactically to patients with cancer with chemotherapy-induced thrombocytopenia at platelet counts of 5000/μL or less, fecal blood loss and red cell transfusion requirements are the same as those for patients transfused prophylactically at higher transfusion triggers of 10 000 platelets/μL or 20 000 platelets/μL. However, the total number of platelet transfusions needed increases significantly, and the duration of the patient's thrombocytopenia tends to be longer at the higher platelet transfusion thresholds. Conclusion A prophylactic platelet transfusion threshold of 5000/μL or greater is sufficient to maintain hemostasis in patients with thrombocytopenia.

BACKGROUND: The impact of donor biology on blood component storability is increasingly appreciated as a determinant of the storage lesion and post-transfusion performances. Platelet metabolism is affected by age and it is critical to platelet responses to activating stimuli in an age-dependent manner. Sex has been previously highlighted as a contributing factor to the platelet proteomics lesion. However, little is known about the impact of donor sex and age on stored platelet metabolism and post-transfusion capacity to circulate. MATERIALS AND METHODS: Apheresis platelets were donated via apheresis by 21 healthy volunteers (12 males and 9 females; ages 20 to 59). Metabolomics analyses were performed at day 0 and after 5 days of storage at 22+2 °C, along with autologous post-transfusion recovery and survival studies with (51)Cr and (111)In. RESULTS: Sex and age significantly impacted platelet metabolism at baseline and upon storage. Platelets from older, male donors were characterised by higher levels of Krebs cycle metabolites, pentose phosphate pathway intermediates and byproducts, deaminated purines and long chain fatty acids. These metabolites ranked amongst the top significant correlates to post-transfusion recoveries. Glutathione homeostasis and sphingosine 1-phosphate were the top positive correlates to long term survival, which was lower in platelets from older, male donors – without reaching statistical significance. DISCUSSION: In this study we report that donor sex and age have a significant impact on platelet metabolism. Novel metabolic correlates to platelet post-transfusion performances (24 h recovery and long-term survival) were identified through high-resolution, stable isotope-labeled internal standard-assisted metabolomics approach.

Background The short dating period of room temperature-stored platelets (PLTs; 5-7 days) limits their availability at far-forward combat facilities and at remote civilian sites in the United States. PLT cryopreservation in 6% DMSO and storage for up to 2 years may improve timely availability for bleeding patients. Study design and methods A dose escalation trial of DMSO-cryopreserved PLTs (CPPs) compared to standard liquid-stored PLTs (LSPs) was performed in bleeding patients with thrombocytopenia. Within each of four cohorts, six patients received escalating doses of CPP (0.5 unit, 1 unit, and sequential transfusions of 2 and 3 units) and one received a LSP transfusion. Patients were monitored for adverse events (AEs), coagulation markers, PLT responses, and hemostatic efficacy. Results Patients with a World Health Organization bleeding score of 2 or more received from 0.5 to 3 units of CPP (n = 24) or 1 unit of LSP (n = 4). There were no related thrombotic or other serious AEs experienced. Mild transfusion-related AEs of chills and fever (n = 1), transient increased respiratory rate (n = 1), DMSO-related skin odor (n = 2), and headache (n = 1) were observed after CPP transfusion. Among CPP recipients 14 of 24 (58%) had improved bleeding scores, including three of seven (43%) patients who had intracerebral bleeding. CPP posttransfusion PLT increments were significantly less than those of LSPs; however, days to next transfusion were the same. After transfusion, the CPP recipients had improvements in some variables of thrombin generation tests and thromboelastography. Conclusion Cryopreserved PLT transfusions appear to be safe and effective when given to bleeding patients with thrombocytopenia.

BACKGROUND Pathogen reduction (PR) of whole blood (WB) may increase blood safety when applied before component separation. This study evaluates the in vivo performance of red blood cells (RBCs) derived from WB treated with the riboflavin and ultraviolet (UV) light PR (Mirasol) system. STUDY DESIGN AND METHODS This was a prospective, two-center, single-blind, randomized, two-period, crossover clinical trial designed to evaluate autologous 51Cr/99mTc-radiolabeled recovery and survival of RBCs derived from Mirasol-treated WB compared to untreated WB. RBCs were stored in AS-3 for 21 days at 1 to 6°C. In vitro RBC variables were characterized. Frequency and severity of treatment-emergent adverse event (TEAE) and neoantigenicity were determined. RESULTS Twenty-four healthy adult volunteers (n = 12 per site) were evaluated. The Mirasol 24-hr RBC recoveries were 82.5 ± 3.9% with one-sided 95% lower confidence limit of 80.9%, meeting US Food and Drug Administration acceptance criteria, albeit at lower level than controls (91.7 ± 6.8%, p

Background Adverse events following blood transfusion include allosensitization and generalized immunosuppression, collectively referred to as transfusion-related immune modulation. We evaluated the immunological effects of red blood cell (RBC) and platelet transfusions on alloantibody responses and on immunoregulatory cells in nonimmunosuppressed patients undergoing cardiovascular surgery. Study design and methods Patients were randomized to receive standard unmodified (STD), leukoreduced (LR), or leukoreduced and γ-irradiated (LRγ) RBCs. Patients received only apheresis platelets that were in-process LR and were γ-irradiated for the third arm. Nontransfused patients served as controls for the effects of surgery itself on immunologic changes. Antibodies to HLA were assessed with use of solid-phase assays. The effects of transfusion on adaptive and innate immunity were evaluated by assessing T regulatory cells (Tregs) and invariant natural killer T (iNKT) cells. Results LR of blood products reduced the development of human leukocyte antigen (HLA) alloantibodies, but only in patients without preexisting HLA antibodies. However, if LR blood products were γ-irradiated, HLA antibody production was not reduced. Compared to nontransfused patients, recipients of STD or LR transfusions showed a significant increase in CD4+CD25hi T cells expressing FoxP3 or CTLA4 and also of iNKT cells producing interleukin-4. In contrast, recipients of LRγ blood products showed markedly lower increases in all three cellular assays. Conclusion LR decreased HLA alloantibody production in naive recipients, but did not reduce the immunosuppressive effects of transfusion. LRγ reduced immunosuppression and was not associated with decreased HLA alloantibody production.

BACKGROUND Transfusion of platelets (PLTs) is a common therapy in a number of clinical settings. However, it is well understood that there is substantial donor-to-donor variation in how well PLTs store and thus the quality of the products that are transfused. The basis of such variation is poorly understood, and there are limited metrics by which units of PLTs can be assessed for their posttransfusion performance. It has repeatedly been demonstrated that myriad biologic changes take place during PLT storage; however, which of the changes correlate with quality of the stored PLTs and/or are mechanistically involved in PLT function remains undetermined. STUDY DESIGN AND METHODS The current study tested stored PLTs from 21 normal subjects, combining high-resolution metabolomics of stored PLTs with in vivo PLT recoveries and survivals. Both individual analytes and metabolic pathways that correlate with posttransfusion PLT viability were identified. RESULTS Caffeine metabolites were associated with poor PLT recovery; caffeine metabolism was not ongoing in the PLT bag and remained at prestorage levels. Acylcarnitines, particular fatty acid metabolites, and oxidized fatty acids were associated with poor PLT survivals. Of the myriad metabolic changes during PLT storage, these are the first reported metabolic findings to begin distinguishing which changes are of functional importance regarding posttransfusion PLT performance. CONCLUSIONS Together, these findings provide novel mechanistic insights into the functional biology of the PLT storage lesion as well as identifying potential targets for modifying donor environment (e.g., caffeine consumption) and also metrics of quality assessment for stored human PLTs.

BACKGROUND In the Trial to Reduce Alloimmunization to Platelets (TRAP) study, 101 of 530 subjects became clinically refractory (CR) to platelets (PLTs) without lymphocytotoxicity assay (LCA)-detectable anti-HLA antibodies. The LCA only detects complement-binding antibodies and is less sensitive than newer assays. Utilizing a more sensitive bead-based assay that does not distinguish between complement-binding versus non–complement-binding antibodies, we have previously shown that while many LCA-negative (LCA–) patients do have anti-HLA antibodies, these low- to moderate-level antibodies do not predict refractoriness. As complement can contribute to PLT rejection, we assessed if previously undetected complement-binding antibodies account for refractoriness among LCA– patients. STUDY DESIGN AND METHODS Samples from 169 LCA– (69 CR, 100 non-CR) and 20 LCA-positive (LCA+; 10 CR, 10 non-CR) subjects were selected from the TRAP study serum repository. Anti-Class I HLA immunoglobulin (Ig)G and C1q-binding antibodies were measured in serum or plasma with bead-based detection assays. Levels of C1q-binding antibodies were compared between CR and non-CR subjects and correlated with corrected count increments (CCIs). RESULTS While some of the LCA– subjects had detectable C1q-binding anti-Class I HLA antibodies, and some LCA+ subjects did not, levels were significantly higher among LCA+ subjects. C1q-binding anti-Class I HLA antibody levels did not differ significantly between CR and non-CR among either the LCA– or the LCA+ subjects. Furthermore, there was no significant correlation observed between CCIs and either C1q-binding or any anti-HLA IgG antibodies. CONCLUSIONS This work confirms that low- to moderate-level anti-Class I antibodies do not drive PLT rejection, suggesting a role for antibody-independent mechanisms.

BACKGROUND Ordinarily, whole blood (WB) is separated into components before storage. We assessed the posttransfusion viability and function of platelets (PLTs) if they were stored within WB at 4°C. STUDY DESIGN AND METHODS Whole blood was obtained from 30 normal subjects and stored at 4°C without agitation for 12 days and for 10, 15, or 22 days with agitation. After WB storage, a PLT concentrate was prepared, and a fresh PLT sample was obtained from each donor. The stored PLTs were labeled with 111 In and the fresh with 51 Cr, and both were simultaneously transfused into their donor. Blood samples were obtained after transfusion to determine PLT recoveries and survivals. PLT samples from WB before and after storage were also assayed for PLT function and biochemistry. RESULTS After storage for 12 days without WB rotation, poststorage PLT counts averaged only 49 ± 12% of baseline values. After storage for 10, 15, or 22 days with end-over-end WB rotation, PLT counts averaged 76 ± 14% of baseline values. Fifteen-day poststorage radiolabeled PLT recoveries averaged 27 ± 11% (49 ± 16% of fresh), and survivals averaged 1.2 ± 0.4 days (16 ± 6% of fresh). in vitro assays demonstrated marked PLT activation after any storage time, and although PLT function decreased over time, stored PLTs were still considered acceptable. CONCLUSION These data suggest that, during rotated WB storage at 4°C for up to 15 days, PLT yields, poststorage PLT recoveries and survivals, and PLT function should be sufficient to support the short-term hemostatic needs of traumatized patients.

Background There continues to be uncertainty about the optimal approach to documenting bleeding data in platelet transfusion trials, with a desire to apply a common assessment tool across all trials. With this in mind, a consensus bleeding assessment tool (BAT) has been developed by the Biomedical Excellence for Safer Transfusion (BEST) collaborative, based on review of data collection forms used in published randomized trials and following content validation with a range of healthcare professionals at seven haematology centres through BEST members. This study aimed to evaluate reliability and reproducibility of the consensus BAT. Methods Replicated clinical assessments of bleeding were undertaken by participants with haematological malignancies recruited at four haematology centres in an international, multicentred, observational study. Concordance of repeat assessments was calculated for agreement in site and grade of bleeding observed. Results Forty patients consented to participate, and 13 trained bleeding assessors collected these data. Bleeding assessments were carried out on 113 separate days. Of all 225 bleeding assessments, 204 were compared for grade concordance, and 160 were compared for site concordance. There was very good grade concordance (83%, 95% confidence interval 74–93%) and good bleeding site concordance (69%, 95% confidence interval 57–79%) in observations of bleeding. Discordance was primarily in relation to assessing skin bleeding. Conclusions Alongside a structured training programme, levels of concordance for a consensus BAT were high. Researchers using assessment tools for bleeding need to balance comprehensive data collection against potential loss of accuracy for some types of bleeding, such as skin findings.

The short dating period of room temperature-stored platelets (PLTs; 5-7 days) limits their availability at far-forward combat facilities and at remote civilian sites in the United States. PLT cryopreservation in 6% DMSO and storage for up to 2 years may improve timely availability for bleeding patients.A dose escalation trial of DMSO-cryopreserved PLTs (CPPs) compared to standard liquid-stored PLTs (LSPs) was performed in bleeding patients with thrombocytopenia. Within each of four cohorts, six patients received escalating doses of CPP (0.5 unit, 1 unit, and sequential transfusions of 2 and 3 units) and one received a LSP transfusion. Patients were monitored for adverse events (AEs), coagulation markers, PLT responses, and hemostatic efficacy.Patients with a World Health Organization bleeding score of 2 or more received from 0.5 to 3 units of CPP (n = 24) or 1 unit of LSP (n = 4). There were no related thrombotic or other serious AEs experienced. Mild transfusion-related AEs of chills and fever (n = 1), transient increased respiratory rate (n = 1), DMSO-related skin odor (n = 2), and headache (n = 1) were observed after CPP transfusion. Among CPP recipients 14 of 24 (58%) had improved bleeding scores, including three of seven (43%) patients who had intracerebral bleeding. CPP posttransfusion PLT increments were significantly less than those of LSPs; however, days to next transfusion were the same. After transfusion, the CPP recipients had improvements in some variables of thrombin generation tests and thromboelastography.Cryopreserved PLT transfusions appear to be safe and effective when given to bleeding patients with thrombocytopenia.

Background The current 5-day storage time of room temperature (22°C)-stored platelets (RSPs) severely limits platelet (PLT) availability. Extended cold (4°C)-stored PLTs (CSPs) are currently being investigated for actively bleeding patients. However, we currently do not know how to best store PLTs in the cold for extended periods of time. In this study, we investigate how storage in plasma and PLT additive solutions (PASs) affects PLT viability in vivo. Study design and methods Twenty normal subjects had a 2-unit hyperconcentrated apheresis PLT collection. One unit was stored at 4°C in plasma for 3 days ("control unit"), and the CSP "test" unit was stored for 10 or 15 days in plasma or 10 days in 35% plasma with either 65% Intersol or Isoplate. After storage, all units were radiolabeled and transfused into their donors. Results For 10-day storage, both the plasma and the Intersol units had significantly better PLT recoveries than the Isoplate units (24% ± 8% vs. 11% ± 3% [55% ± 11% vs. 21% ± 8% as percentage of control data], p = 0.002; and 18% ± 4% vs. 11% ± 3% [43% ± 6% vs. 21% ± 8% as percentage of control data], p = 0.004, respectively). There was a trend for lower PLT recoveries with Intersol compared to plasma (p = 0.056). PLT survivals and most in vitro measurements did not differ significantly among the units. Conclusions While the in vitro variables suggest largely comparable results between plasma and PASs, in vivo recoveries were higher with plasma compared with both Intersol and Isoplate (p = 0.057 and p = 0.002, respectively). Whether this difference leads to clinically relevant differences in hemostatic efficacy remains to be determined.

Patients with hypoproliferative thrombocytopenia are at an increased risk for hemorrhage and alloimmunization to platelets. Updated guidance for optimizing platelet transfusion therapy is needed as data from recent pivotal trials have the potential to change practice. This guideline, developed by a large international panel using a systematic search strategy and standardized methods to develop recommendations, incorporates recent trials not available when previous guidelines were developed. We found that prophylactic platelet transfusion for platelet counts less than or equal to 10 × 10 9 /L is the optimal approach to decrease the risk of hemorrhage for patients requiring chemotherapy or undergoing allogeneic or autologous transplantation. A low dose of platelets (1.41 × 10 11 /m 2 ) is hemostatically as effective as higher dose of platelets but requires more frequent platelet transfusions suggesting that low-dose platelets may be used in hospitalized patients. For outpatients, a median dose (2.4 × 10 11 /m 2 ) may be more cost-effective to prevent clinic visits only to receive a transfusion. In terms of platelet products, whole blood–derived platelet concentrates can be used interchangeably with apheresis platelets, and ABO-compatible platelet should be given to improve platelet increments and decrease the rate of refractoriness to platelet transfusion. For RhD-negative female children or women of child-bearing potential who have received RhD-positive platelets, Rh immunoglobulin should probably be given to prevent immunization to the RhD antigen. Providing platelet support for the alloimmunized refractory patients with ABO-matched and HLA-selected or crossmatched products is of some benefit, yet the degree of benefit needs to be assessed in the era of leukoreduction.

Bleeding remains a significant problem for many thrombocytopenic hematology/oncology patients in spite of platelet transfusions. Factors that might contribute to bleeding were analyzed for 16 320 patient-days on or after their first platelet transfusion in 1077 adult patients enrolled in the Platelet Dose (PLADO) trial. All patients had a greatly increased risk of bleeding at platelet counts of ≤5 × 109/L (odds ratio [OR], 3.1; 95% confidence interval [CI], 2.0-4.8) compared with platelet counts ≥81 × 109/L. Platelet counts between 6 × 109/L and 80 × 109/L were also associated with a somewhat elevated bleeding risk in patients receiving allogeneic stem cell transplants (SCTs) or chemotherapy but not in those undergoing autologous SCTs. Other significant laboratory predictors of bleeding were hematocrit ≤25% (OR, 1.29; 95% CI, 1.11-1.49), activated partial thromboplastin time (aPTT) 30 to ≤50 seconds (OR, 1.40; 95% CI, 1.08-1.81; P = .01), aPTT >50 seconds (OR, 2.34; 95% CI, 1.54-3.56), international normalized ratio (INR) 1.2 to 1.5 (OR, 1.46; 95% CI, 1.17-1.83), and INR >1.5 (OR, 2.05; 95% CI, 1.43-2.95). Transfusion of either platelets or red blood cells (RBCs) on days with bleeding was often not sufficient to change bleeding outcomes on the following day. Because bleeding occurred over a wide range of platelet counts among patients undergoing allogeneic SCT or chemotherapy and because platelet transfusions may not prevent bleeding, other risk factors may be involved. These may include low hematocrit and coagulation abnormalities. This trial was registered at www.clinicaltrials.gov as #NCT00128713.

BACKGROUND How platelet (PLT) product characteristics such as dose, source (whole blood-derived (WBD) vs. apheresis), storage duration, and ABO matching status affect the risks of transfusion-related adverse events (TRAEs) is unclear. Similarly, more information is needed to define how recipient characteristics affect the frequency of TRAEs following PLT transfusion.

Background Platelet (PLT) concentrates (PCs) prepared from whole blood in the United States are made using the PLT-rich plasma method. The PCs must be made within 8 hours of blood collection and stored for only 5 days. In Europe and Canada, PCs are made using the buffy coat (BC) method from whole blood held overnight at 22°C and storage times may be up to 7 days. Our studies were designed to determine how long BC PLTs can be stored in plasma or Plasmalyte while meeting the FDA's poststorage viability criteria. Study Design and Methods Normal subjects donated whole blood that was stored at 22°C for 22 ± 2 hours before preparation of BC PLTs. PLTs were stored for 5 to 8 days in either plasma or Plasmalyte concentrations of 65 or 80%. Radiolabeled autologous stored versus fresh PLT recoveries and survivals were assessed as well as poststorage in vitro assays. Results BC PLTs stored in either plasma or 65% Plasmalyte met FDA poststorage PLT recovery criteria for 7 days but survivals for only 6 days, while storage in 80% Plasmalyte gave very poor results. Both stored PLT recoveries and survivals correlated with the same donor's fresh results, but the correlation was much stronger between recoveries than survivals. In vitro measures of extent of shape change, morphology score, and pH best predicted poststorage PLT recoveries, while annexin V binding best predicted PLT survivals. Conclusion BC PLTs stored in either plasma or 65% Plasmalyte meet FDA's poststorage viability criteria for 6 days.

To evaluate the poststorage viability of apheresis platelets stored for up to 18 days in 80% platelet additive solution (PAS)/20% plasma, 117 healthy subjects donated platelets using the Haemonetics MCS+, COBE Spectra (Spectra), or Trima Accel (Trima) systems. Control platelets from the same subjects were compared with their stored test PAS platelets by radiolabeling their stored and control platelets with either (51)chromium or (111)indium. Trima platelets met Food and Drug Administration poststorage platelet viability criteria for only 7 days vs almost 13 days for Haemonetics platelets; ie, platelet recoveries after these storage times averaged 44 ± 3% vs 49 ± 3% and survivals were 5.4 ± 0.3 vs 4.6 ± 0.3 days, respectively. The differences in storage duration are likely related to both the collection system and the storage bag. The Spectra and Trima platelets were hyperconcentrated during collection, and PAS was added, whereas the Haemonetics platelets were elutriated with PAS, which may have resulted in less collection injury. When Spectra and Trima platelets were stored in Haemonetics' bags, poststorage viability was significantly improved. Platelet viability is better maintained in vitro than in vivo, allowing substantial increases in platelet storage times. However, implementation will require resolution of potential bacterial overgrowth during storage.

Background Both leukoreduction and ultraviolet (UV) light treatment of blood products have been shown to reduce the incidence of HLA antibody development in recipients, but the impact of these treatments on the magnitude and persistence of the antibody response is less clear. Study Design and Methods Longitudinal samples from 319 subjects taken from four different study cohorts were evaluated for HLA antibodies to determine the effects of leukoreduction and UV treatment on HLA antibody generation and persistence. Results Subjects receiving leukoreduced or UV-treated blood products were less likely to generate Class I HLA antibodies, and those receiving leukoreduced blood were also less likely to generate Class II HLA antibodies. Among those receiving nonleukoreduced blood, 55% developed Class I HLA antibodies and 51% developed Class II HLA antibodies compared with 28% (Class I) and 15% (Class II) for those receiving leukoreduced blood and 36% (Class I) and 54% (Class II) for those receiving UV-treated blood. Among alloimmunized subjects, leukoreduction resulted in a significant twofold reduction in the magnitude of Class I HLA antibodies, and UV treatment resulted in a significant threefold reduction in the magnitude of Class II HLA antibodies. Both treatments resulted in shorter persistence of Class I HLA antibodies. Conclusions These data demonstrate that leukoreduction and UV treatment of blood products results not only in a reduction in the incidence of HLA antibody production, but also in lower and more transient HLA antibody levels among sensitized transfusion recipients.

Background Many platelet (PLT) transfusion trials now use bleeding as a primary outcome; however, previous studies have shown a wide variation in the amount (5%-70%) and type of bleeding documented. Differences in the way bleeding has been identified, recorded, and graded may account for some of this variability. This study's aim was to compare trials' method to document and grade bleeding. Study Design and Methods Data were collected via three methods: a review of study publications, study case report forms, and a questionnaire sent to the authors. Authors of randomized controlled trials of PLT transfusion that used bleeding as an outcome measure were identified from the searches reported by two recent systematic reviews. Twenty-four authors were contacted, and 13 agreed to participate. Data submitted were reviewed and summarized. Results More recent studies with trained bleeding assessors, detailed documentation, and expanded grading systems have reported higher overall levels of bleeding. The World Health Organization grading system was widely used to grade bleeding, but there was no consistency in the bleeding grade definitions. For example, bleeding classified as Grade 2 in some studies (spreading petechiae) was classified as Grade 1 in other studies. Conclusions This study has highlighted differences in the method of recording and grading bleeding, which may account for some of the variation in reported bleeding rates. To ensure that differences between studies can be attributed to trial interventions or types of participant included, this study group is developing consensus bleeding definitions, a standardized approach to record and grade bleeding, and guidance notes to educate and train bleeding assessors.

Quality management of blood products is essential for blood banking. It is influenced by both processing and donor characteristics and assured by monitoring routine in vitro parameters to defined product specifications. However, these measures correlate poorly with the in vivo behavior of transfused platelets and cannot be used to select optimal donors. Since radiolabeled platelet recovery and survival studies are expensive and time consuming, there is an ongoing search for simpler measures that predict platelet transfusion outcomes. We performed a pilot study using semi-qualitative proteomics to assess changes in the platelet protein profile of donors with either acceptable or unacceptable in vivo radiolabeled autologous platelet recovery and survival measurements. Proteins changing during a 9-day storage period included cytoskeletal elements talin, vinculin and moesin as well as signal transduction proteins 14-3-3, RhoGDI and Rap1. Two of nine donations exhibited a decrease in these proteins and poor in vivo platelet recovery and survival whereas the remaining donors showed acceptable platelet recovery and survival and expected protein profiles. Analyses revealed a significant correlation between protein levels of Rap1 and RhoGDI during storage and platelet recovery and survival. This study provides for the first time preliminary data showing evidence of the utility of protein profiling to predict platelet transfusion quality. This article is part of a Special Issue entitled: Integrated omics.

Pathogen reduction (PR) of whole blood (WB) may increase blood safety when applied before component separation. This study evaluates the in vivo performance of red blood cells (RBCs) derived from WB treated with the riboflavin and ultraviolet (UV) light PR (Mirasol) system.This was a prospective, two-center, single-blind, randomized, two-period, crossover clinical trial designed to evaluate autologousTwenty-four healthy adult volunteers (n = 12 per site) were evaluated. The Mirasol 24-hr RBC recoveries were 82.5 ± 3.9% with one-sided 95% lower confidence limit of 80.9%, meeting US Food and Drug Administration acceptance criteria, albeit at lower level than controls (91.7 ± 6.8%, p 0.001). Mean RBC survival and TRBCs derived from Mirasol WB and stored for up to 21 days in AS-3 maintained acceptable cell quality and recovery, albeit modestly reduced compared with untreated RBCs. Mirasol WB may represent a valid single WB PR platform that allows manufacture of RBC for storage for up to 21 days.

Human lymphocyte antigen alloimmunization to filter leukoreduced (F-LR) platelets occurs in about 18% of immunosuppressed thrombocytopenic hematology/oncology patients and represents a significant challenge for effective chemotherapy. In a dog platelet transfusion model, we have evaluated other methods of preventing alloimmune platelet refractoriness and demonstrated that successful methods in our dog model are transferable to man. In the present study, donor/recipient pairs were dog lymphocyte antigen DR-B incompatible (88% of the pairs), and recipient dogs received up to 8 weekly treated transfusions from a single donor (a highly immunogenic stimulus), or until platelet refractoriness. Continued acceptance of F-LR platelets occurred in 6 of 13 recipients (46%), but neither γ-irradiation (γ-I; 0 of 5) nor Mirasol pathogen reduction (MPR; 1 of 7) treatment of donor platelets prevented alloimmune platelet refractoriness. Combining γ-I with F-LR was associated with only 2 of 10 (20%) recipients accepting the transfused platelets. Surprisingly, F-LR platelets that then underwent MPR were accepted by 21 of 22 (95%) recipients (P < .001 vs F-LR + γ-I recipients). Furthermore, 7 of 21 (33%) of these accepting recipients demonstrated specific tolerance to 8 more weekly donor transfusions that had not been treated. In addition, platelet concentrates prepared from F-LR + MPR whole blood were also nonimmunogenic; that is, 10 of 10 (100%) recipients accepted donor platelets. Overall, 31 of 32 (97%) recipients accepted F-LR + MPR platelets; none developed antibodies to donor lymphocytes. These data are the highest rate of acceptance for platelet transfusions reported in either animals or man. This approach to platelet transfusion may be particularly important when supporting patients with intact immune systems, such as in myelodysplastic syndromes.

BACKGROUND: A systematic review of randomized controlled trials and observational studies assessing platelet (PLT) transfusion therapy identified gaps in the descriptions of trial design, variables of the PLT products transfused, and outcomes. We aimed to systematically develop a reporting guideline to aid in designing, reporting, and critiquing PLT trials. STUDY DESIGN AND METHODS: With the use of expert opinion, a preliminary checklist of 23 items was created. The Delphi method, an iterative forecasting method, was used to achieve consensus among experts to systematically improve upon the preliminary checklist. Items were ranked for inclusion using a 7-point Likert scale from “definitely should not” to “very important to” include. Criteria were established a priori based on the mean score: at least 5.5 accept, 2.6 to 5.4 intermediate, and not more than 2.5 eliminate. Intermediate items were edited and sent out in subsequent rounds for review. Three rounds were undertaken to determine the final checklist. RESULTS: Initially 33 experts participated, decreasing to 25 by the third round. The preliminary checklist consisted of 23 items spread over four sections: methods and intervention, PLT-specific outcomes, PLT-specific results, and PLT-specific adverse events. After three rounds of the Delphi method, the checklist was expanded and refined to include 30 items. The final checklist was further enhanced by adding an explanatory guide. CONCLUSION: Use of the Delphi method was successful in finding consensus on items to include in reports of a clinical PLT transfusion study. The final checklist and explanatory guide will be useful for authors and editors to improve the reporting of PLT transfusion trials.

Age-group analyses were conducted of patients in the prophylactic platelet dose trial (PLADO), which evaluated the relation between platelet dose per transfusion and bleeding. Hospitalized patients with treatment-induced hypoproliferative thrombocytopenia were randomly assigned to 1 of 3 platelet doses: 1.1 × 1011, 2.2 × 1011, or 4.4 × 1011 platelets/m2 per transfusion, given for morning counts of ≤ 10 000 platelets/μL. Daily hemostatic assessments were performed. The primary end point (percentage of patients who developed grade 2 or higher World Health Organization bleeding) was evaluated in 198 children (0-18 years) and 1044 adults. Although platelet dose did not predict bleeding for any age group, children overall had a significantly higher risk of grade 2 or higher bleeding than adults (86%, 88%, 77% vs 67% of patients aged 0-5 years, 6-12 years, 13-18 years, vs adults, respectively) and more days with grade 2 or higher bleeding (median, 3 days in each pediatric group vs 1 day in adults; P < .001). The effect of age on bleeding differed by disease treatment category and was most pronounced among autologous transplant recipients. Pediatric subjects were at higher risk of bleeding over a wide range of platelet counts, indicating that their excess bleeding risk may be because of factors other than platelet counts. This trial was registered at www.clinicaltrials.gov as #NCT00128713.

Platelet characteristics, such as platelet dose, platelet source (apheresis vs pooled), platelet donor-recipient ABO compatibility, and duration of platelet storage, can affect posttransfusion platelet increments, but it is unclear whether these factors impact platelet transfusion efficacy on clinical bleeding. We performed secondary analyses of platelet transfusions given in the prospective randomized Platelet Dose Study, which included 1272 platelet-transfused hematology-oncology patients who received 6031 prophylactic platelet transfusions. The primary outcome of these analyses was time from first transfusion to first World Health Organization ≥ grade 2 bleeding. Platelet transfusion increments were assessed at 0.25 to 4 hours and 16 to 32 hours after platelet transfusion. There were 778 patients evaluable for analysis of time to bleeding. Adjusted models showed that randomized dose strategy, platelet source, ABO compatibility, and duration of storage did not predict this outcome. Platelet increments were generally higher for transfusions of apheresis platelets, ABO-identical platelets, and platelets stored 3 days versus 4 to 5 days. Thus, although platelet source, ABO compatibility, and duration of storage exert a modest impact on both absolute and corrected posttransfusion platelet increments, they have no measurable impact on prevention of clinical bleeding. This trial was registered at www.clinicaltrials.gov as #NCT00128713.

BACKGROUND: The Food and Drug Administration (FDA) requires that red blood cells must be refrigerated within 8 hours of whole blood collection. Longer storage of whole blood at 22°C before component preparation would have many advantages. STUDY DESIGN AND METHODS: Two methods of holding whole blood for 20 to 24 hours at room temperature were evaluated, refrigerated plates or a 23°C incubator. After extended whole blood storage, platelet (PLT) concentrates were prepared from PLT-rich plasma on Day 1 postdonation, and the PLTs were stored for 6 more days. On Day 7 of PLT storage, blood was drawn from each subject to prepare fresh PLTs. The stored and fresh PLTs were radiolabeled and transfused into their donor. RESULTS: Eleven subjects' whole blood was stored using refrigerated butanediol plates (Compocool, Fresenius), and 10 using an incubator. Poststorage PLT recoveries averaged 47 ± 13% versus 53 ± 11% and survivals averaged 4.6 ± 1.7 days versus 4.7 ± 0.9 days for Compocool versus incubator storage, respectively (p = NS). With all results, poststorage PLT recoveries averaged 75 ± 10% of fresh and survivals 57 ± 13% of fresh; PLT recoveries met FDA guidelines for poststorage PLT viability but not survivals. CONCLUSION: Seven-day poststorage PLT viability is comparable when whole blood is stored for 22 ± 2 hours at 22°C using either refrigerated plates or an incubator to maintain temperature before preparing PLT concentrates.

Background and Objectives Platelet alloimmunization and refractoriness to platelet transfusion are complications of platelet transfusion therapy. The platelet dose (PLADO) trial, as the largest prospective randomized trial of prophylactic platelet therapy to date, afforded an opportunity to analyse these two issues. Materials and Methods PLADO patient records were examined for evidence of platelet alloimmunization, defined as an increase in HLA Class I panel-reactive antibodies (PRA) to ≥20%, and clinical refractoriness, defined as two consecutive ≤4 h posttransfusion corrected platelet count increments (CCI) of

In the Trial to Reduce Alloimmunization to Platelets (TRAP) study, 101 of 530 subjects became clinically refractory (CR) to platelets (PLTs) without lymphocytotoxicity assay (LCA)-detectable anti-HLA antibodies. The LCA only detects complement-binding antibodies and is less sensitive than newer assays. Utilizing a more sensitive bead-based assay that does not distinguish between complement-binding versus non-complement-binding antibodies, we have previously shown that while many LCA-negative (LCA-) patients do have anti-HLA antibodies, these low- to moderate-level antibodies do not predict refractoriness. As complement can contribute to PLT rejection, we assessed if previously undetected complement-binding antibodies account for refractoriness among LCA- patients.Samples from 169 LCA- (69 CR, 100 non-CR) and 20 LCA-positive (LCA+; 10 CR, 10 non-CR) subjects were selected from the TRAP study serum repository. Anti-Class I HLA immunoglobulin (Ig)G and C1q-binding antibodies were measured in serum or plasma with bead-based detection assays. Levels of C1q-binding antibodies were compared between CR and non-CR subjects and correlated with corrected count increments (CCIs).While some of the LCA- subjects had detectable C1q-binding anti-Class I HLA antibodies, and some LCA+ subjects did not, levels were significantly higher among LCA+ subjects. C1q-binding anti-Class I HLA antibody levels did not differ significantly between CR and non-CR among either the LCA- or the LCA+ subjects. Furthermore, there was no significant correlation observed between CCIs and either C1q-binding or any anti-HLA IgG antibodies.This work confirms that low- to moderate-level anti-Class I antibodies do not drive PLT rejection, suggesting a role for antibody-independent mechanisms.

In April 2010, a working group sponsored by the National Heart, Lung, and Blood Institute was assembled to identify research strategies to improve our understanding of alloimmunization caused by the transfusion of allogeneic blood components and to evaluate potential approaches to both reduce its occurrence and manage its effects. Significant sequelae of alloimmunization were discussed and identified, including difficulties in maintaining chronic transfusion of red blood cells and platelets, hemolytic disease of the newborn, neonatal alloimmune thrombocytopenia, and rejection of transplanted cells and tissues. The discussions resulted in a consensus that identified key areas of future research and developmental areas, including genetic and epigenetic recipient factors that regulate alloimmunization, biochemical specifics of transfused products that affect alloimmunization, and novel technologies for high-throughput genotyping to facilitate extensive and efficient antigen matching between donor and recipient. Additional areas of importance included analysis of unappreciated medical sequelae of alloimmunization, such as cellular immunity and its effect upon transplant and autoimmunity. In addition, support for research infrastructure was discussed, with an emphasis on encouraging collaboration and synergy of animal models biology and human clinical research. Finally, training future investigators was identified as an area of importance. In aggregate, this communication provides a synopsis of the opinions of the working group on the above issues and presents both a list of suggested priorities and the rationale for the topics of focus. The areas of research identified in this report represent potential fertile ground for the medical advancement of preventing and managing alloimmunization in its different forms and mitigating the clinical problems it presents to multiple patient populations.

BACKGROUND: A recent review concluded that there was inadequate evidence to show a difference between buffy coat (BC) and platelet (PLT)-rich plasma (PRP) PLT concentrates prepared from whole blood. We hypothesized that 7-day-stored BC-PLTs would have superior autologous recoveries and survivals compared to PRP-PLTs and that both would meet the Food and Drug Administration (FDA) criteria for poststorage viability. STUDY DESIGN AND METHODS: This was a randomized, crossover study design in healthy subjects who provided informed consent. Each participant donated a unit of whole blood on two occasions. In random order, either BC-PLTs or PC-PLTs were prepared after a 20 ± 2°C overnight hold of the whole blood. PLTs were stored under standard conditions. On Day 7, fresh PLTs were prepared from 43 mL of autologous whole blood. The fresh PLTs paired with either BC-PLTs or PRP-PLTs were alternately labeled with 111In or 51Cr and simultaneously reinfused to determine recoveries and survivals. In vitro assays were performed on Days 1 and 7. RESULTS: Fourteen subjects completed the study at two sites. No differences in poststorage PLT viabilities were observed between BC-PLTs and PRP-PLTs; recovery differences averaged 3.7 ± 2.4% (±SE, p = 0.15) and survival differences averaged 0.48 ± 0.56 days (p = 0.41). Neither type of PLTs met the current FDA criteria for either poststorage PLT recoveries or survivals. CONCLUSION: We were unable to demonstrate that single-unit BC-PLTs stored for 7 days have superior poststorage viability compared to PRP-PLTs. Failure to meet the minimum FDA criteria for poststorage PLT viability raises questions regarding the acceptance thresholds of these metrics.

Functional white blood cells (WBCs) in blood components may be responsible for a number of adverse transfusion effects, including transfusion-associated graft-versus-host disease (TA-GVHD), alloimmunization, and alloimmune platelet (PLT) refractoriness. TA-GVHD occurs when functional lymphocytes are transfused into a patient who is unable to mount an immune response to the human leukocyte antigen (HLA) due to HLA compatibility or immunosuppression. Alloantibodies against HLA antigens on donor WBCs and PLTs are the major cause of refractoriness to PLT transfusions in patients receiving repeated blood transfusions. Attempts to reduce these undesirable effects have included leukoreduction filters and gamma irradiation. Studies have shown that exposure of PLT concentrates to riboflavin and light (Mirasol pathogen reduction technology [PRT], CaridianBCT Biotechnologies) causes irreparable modifications of nucleic acids that result in inactivation of a wide range of pathogens as well as inhibition of the immunologic responses mediated by WBCs present in PLT concentrates. This article summarizes these studies and also reports on additional findings from the Trial to Reduce Alloimmunization to Platelets (TRAP) and Mirasol Clinical Evaluation (MIRACLE) trials. Data from in vitro studies and this clinical trial suggest that PRT treatment may be as effective as gamma irradiation in preventing TA-GVHD and more effective than leukoreduction in preventing alloimmunization.

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.

Background Using bacterial detection or pathogen reduction, extended platelet storage may be licensed if platelet viability is maintained. FDA's post-storage platelet acceptance guidelines are that autologous stored platelet recoveries and survivals should be ≥66% and ≥58%, respectively, of each donor's fresh platelet data.

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.

Objectives Three leucoreduction filters were evaluated – when used alone or combined with centrifuge leucoreduction (C-LR) – to prevent alloimmune platelet refractoriness in a dog platelet transfusion model. Materials and Methods Donor platelet-rich plasma (PRP) or buffy coat (BC) platelets were either filter leucoreduced (F-LR) or F-LR/C-LR, 51Cr radiolabelled and transfused. Weekly transfusions were given for up to 8 weeks or until platelet refractoriness. Recipients who accepted treated transfusions were then given non-leucoreduced (non-LR) platelets to determine whether donor-specific tolerance had been induced. Results Acceptance of F-LR PRP transfusions ranged from 29% to 66%. F-LR/C-LR transfusions prepared from PRP were accepted by 92%, from BC by 63% and from pooled PRP by 75% of recipients (p=NS); overall acceptance rate of F-LR/C-LR transfusions was 83%. Tolerance to subsequent non-LR transfusions occurred in 45% of the F-LR-/C-LR-accepting recipients unrelated to DR-B compatibility between donors and recipients (P = 0·18). Conclusion In a dog platelet transfusion model, acceptance of donor platelets required combining F-LR with C-LR as apparently each process removes different immunizing WBCs.

BACKGROUND The pH environment of stored platelet (PLT) products is recognized as an important factor and is generally used as a key surrogate measure of PLT viability. It is the only in vitro measurement that has been translated into industry standards and regulatory rules or specifications for storage of PLT products. The objective of this study was to evaluate the effect of in vitro pH on the in vivo recovery and survival of autologous PLT products. STUDY DESIGN AND METHODS Data from individual autologous radiolabeled PLT kinetic studies were solicited from independent laboratories. PLTs stored for at least 5 days in 100 percent autologous plasma with a pH(22 degrees C) of at least 6.2 were analyzed. Data were fit to a mixed-effects regression model with fixed effects of pH(22 degrees C), time of storage, and preparation method-storage bag combination. RESULTS Eight research laboratories reported 476 individual recovery and survival results with associated pH before labeling from a variety of autologous, radiolabeled PLT kinetic studies from September 1999 to March 2005. These results are from 254 individual subjects who donated a total of 386 PLT units, with up to nine collections per subject reported. The effect of pH on either PLT recovery (p = 0.86) or survival (p = 0.55) was not significant. Time of storage and the method-bag combination both had significant effects on these outcomes (p < 0.0001). CONCLUSION These data suggest that there is no relationship between in vitro pH at a pH(22 degrees C) of at least 6.2 and in vivo PLT viability as measured by radiolabeled recovery and survival of autologous PLTs.

Outlined is the background and rationale for the initiation of a randomized prospective platelet transfusion trial to evaluate the effects of platelet dose on hemostasis and platelet utilization rates. This clinical trial is being performed by the newly established Transfusion Medicine/Hemostasis Clinical Trial Network supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health. The trial will randomize 1,350 patients into three platelet transfusion arms based on body surface area (BSA). The lower dose will be 1.1 × 1011 platelets/m2, the medium dose will be 2.2 × 1011 platelets/m2, and the higher dose will be 4.4 × 1011 platelets/m2. The primary outcome measure will be the incidence of Grade 2 bleeding; i.e., gross hemorrhage without the need for red cell transfusion. Major secondary outcome measures will be the total number of platelets transfused, the total number of platelet transfusion events, the highest grade of bleeding, and bleeding severity. It is expected that this clinical trial will change platelet transfusion practice by identifying whether low-dose platelet transfusion therapy provides adequate hemostasis and what is the most cost-effective strategy for providing platelet transfusions. J. Clin. Apheresis 21: 78–84, 2006. © 2006 Wiley-Liss, Inc.

BACKGROUND: The SPRINT trial examined efficacy and safety of photochemically treated (PCT) platelets (PLTs). PCT PLTs were equivalent to untreated (control) PLTs for prevention of bleeding. Transfused PLT dose and corrected count increments (CIs), however, were lower and transfusion intervals were shorter for PCT PLTs, resulting in more PCT than control transfusions. PLT dose was analyzed to determine the impact of the number of PLTs transfused on transfusion requirements. STUDY DESIGN AND METHODS: Transfusion response was compared for patients with all doses of ≥3.0 × 1011 and the complementary subset of patients with any dose of fewer than 3.0 × 1011. Analyses included comparison of bleeding, number of PLT and red blood cell (RBC) transfusions, transfusion intervals, and CIs between PCT and control groups within each PLT dose subset. RESULTS: Mean PLT dose per transfusion in the PCT group was lower than in the control group (3.7 × 1011 vs. 4.0 × 1011; p

A variety of patientand product-related factors influenced the outcome of 6379 transfusions given to 533 patients in the Trial to Reduce Alloimmunization to Platelets (TRAP). Responses measured were platelet increments, interval between platelet transfusions, and platelet refractoriness. Patient factors that improved platelet responses were splenectomy and increasing patient age. In contrast, at least 2 prior pregnancies, male gender, splenomegaly, bleeding, fever, infection, disseminated intravascular coagulation, increasing height and weight, lymphocytotoxic antibody positivity, an increasing number of platelet transfusions, or receiving heparin or amphotericin were associated with decreased posttransfusion platelet responses. Platelet factors that were associated with improved platelet responses were giving ABO-compatible platelets, platelets stored for 48 hours or less, and giving large doses of platelets while ultraviolet B (UV-B) or gamma irradiation decreased platelet responses. However, in alloimmunized lymphocytoxic antibody-positive patients, the immediate increment to UV-B-irradiated platelets was well maintained, whereas all other products showed substantial reductions. Refractoriness to platelet transfusions developed in 27% of the patients. Platelet refractoriness was associated with lymphocytotoxic antibody positivity, heparin administration, fever, bleeding, increasing number of platelet transfusions, increasing weight, at least 2 pregnancies, and male gender. The only factors that reduced platelet refractoriness rates were increasing the dose of platelets transfused or transfusing filtered apheresis platelets.

The effectiveness of different methods of leukoreduction in preventing alloimmune platelet refractoriness was evaluated in a canine model. Platelets from a random donor dog were administered for up to 8 weeks or until platelet refractoriness. Standard (STD; unmodified) platelets were accepted by 14% of recipients (n = 7) compared with 14% for centrifuge leukoreduced (C-LR) platelets (n = 21) and 31% for filter leukoreduced (F-LR) platelets (n = 13; no significant differences). Surprisingly, using both F-LR and C-LR platelets was highly effective (87% acceptance, n = 15). Transfusing F-LR/C-LR red blood cells (n = 4) or F-LR/C-LR plasma (n = 4), along with F-LR/C-LR platelets, did not affect platelet acceptance (100% acceptance). Overall acceptance of F-LR/C-LR platelets was 91% (n = 23; P ≤ .05 versus STD, C-LR, or F-LR platelets). F-LR/C-LR transfusions also induced tolerance to subsequent STD platelet transfusions from the same donor (82% acceptance, n = 19) as well as to donor skin grafts without recipient immunosuppression (57% acceptance, n = 7). To evaluate mechanisms of tolerance induction, F-LR/C-LR platelets were γ-irradiated. Although the γ-irradiated F-LR/C-LR platelets were uniformly accepted (n = 6), tolerance to STD platelets was lost. These data suggest that some allostimulatory white cells are filter adherent, whereas others escape filtration but can be removed by centrifugation and tolerance requires a residual functioning white cell.

BACKGROUND: During the Trial to Reduce Alloimmunization to Platelets (TRAP Trial), data were prospectively collected for 8769 PLT transfusions regarding the frequency of moderate to severe PLT transfusion reactions. STUDY DESIGN AND METHODS: At seven centers, 598 patients were randomly assigned to receive unmodified pooled random-donor PLT concentrates (PCs), UV-B-irradiated PCs, filtered PCs, or filtered random-donor apheresis PLTs. RESULTS: Moderate to severe transfusion reactions were an increase in temperature of at least 2°C, chills with rigors, extensive urticaria, dyspnea, cyanosis, or bronchospasm. These reactions occurred with 2.2 percent of the transfusions in 22 percent of the patients. Transfusion reactions were associated with WBC counts of more than 5 × 106 per transfusion (p = 0.002) and transfusions stored for more than 48 hours (p = 0.02). PLT counts before transfusion were significantly lower for transfusions associated with reactions (p = 0.005). Neither UV-B irradiation nor apheresis PLTs independently influenced reaction rates. The PLT increment at 1 hour after transfusion was lower for transfusions associated with reactions (p = 0.004), and the frequency of reactions was higher in PLT refractory patients (p < 0.001). CONCLUSIONS: The provision of either fresh and/or WBC-reduced PLTs may decrease the frequency of PLT transfusion reactions and improve PLT transfusion efficacy.

To characterize recombinant human macrophage-colony stimulating factor (rhM-CSF)-associated thrombocytopenia (TCP), in vivo studies were performed in dogs, including the biodistributions and recoveries of radiolabelled autologous and allogeneic platelets. rhM-CSF induced a reversible, dose-dependent decrease in platelet counts. The number of megakaryocytes in spleen and marrow of rhM-CSF-treated dogs was increased two to threefold. Recoveries of allogeneic platelets transfused from rhM-CSF-treated donors into tolerized recipients (n = 3) were not significantly different from allogeneic baseline studies (93 +/- 10% of baseline values at 24 h and 90 +/- 1% at 40 h), whereas autologous platelets infused back into rhM-CSF-treated donors had decreased recoveries (45 +/- 2% of baseline values at 24 h, P = 0.03 and 20 +/- 4% at 40 h, P = 0.001). Platelet biodistribution studies showed increased accumulation of radiolabelled platelets over the spleens and livers of rhM-CSF-treated dogs. Histochemistry showed increased levels of platelet-specific antigen (CD41; glycoprotein IIb) associated with Kupffer cells. The sensitivity of platelets from rhM-CSF-treated dogs to activation from thrombin, as measured by expression of P-selectin (CD62P), was not significantly different when compared with baseline studies (P = 0.18; n = 4). These results support the concept that rhM-CSF induces an activation of the monocyte-macrophage system (MMS), which causes a reversible TCP in a dog model.

e12521 Background: T-DM1 treatment results in Grade 3-4 thrombocytopenia in 8%-13% (1.4% with clinically significant bleeding). Prior in vitro studies reported T-DM1 inhibition of megakaryocyte maturation as the cause of decreased platelet production. The current study was initiated to evaluate the cause of thrombocytopenia in patients. Methods: Patients with HER2-positive metastatic breast cancer (N = 10) were enrolled in this Phase 1 study. 111In radiolabeled autologous platelet recoveries and survivals as well as serial platelet counts, bleeding time assays, platelet aggregation responses to epinephrine, adenosine diphosphate, collagen, arachidonic acid, ristocetin, and thromboxane were performed at baseline and during two consecutive cycles (C) of the drug (3.6mg/kg IV q3weeks). Results: Platelet nadir occurred on days (D) 7, 8, or 9 post-T-DM1 in C1 and at D5-6 in C2. Average nadir counts (% baseline) in C1 and C2 were 116,000/µl (52 ±22%) and 117,000/µl (48 ±31%), respectively, with return to baseline by D15 in both cycles. Autologous 111In-labeled platelet recoveries averaged 64 ±10%, 65 ±12%, and 65 ±12% at baseline, C1 and C2, respectively. Baseline platelet survival averaged 8.8 (±1.1) days but progressively shortened to 5.4 (±1.6) days during C1 and 4.6 (±1.0) days during C2 (p < 0.001 compared to baseline for both cycles). Bleeding times were appropriate for the corresponding platelet count throughout both cycles. Aggregation responses to all agonists decreased during the study, more in C2 than in C1. Conclusions: Following T-DM1 administration, platelet kinetic measurements demonstrated statistically significant progressive decreases in platelet survivals from normal baseline values (decreased survivals were observed in all patients treated on study). In distinction to published in vitro studies, these unexpected results indicate a direct toxic effect of T-DM1 on patients’ autologous circulating platelets. In addition, autologous aggregation responses were decreased, suggesting drug-induced platelet dysfunction. Clinical trial information: NCT01816035.

This grant pertains to finding novel approaches for storage of platelets for transfusion. Our project proposes to determine the efficacy of using a pathogen inactivation technique (Mirasol) coupled with a platelet additive solution (PAS) to extend the life of stored platelets. Our project also aims to determine how long acceptable platelet viability can be maintained in platelets stored at 4C.