Apheresis Platelet Units Research Articles

Paid platelet donors: Points to consider

Paid platelet donors: Points to consider

Indications for transfusion of blood components

Indications for transfusion of blood components

Assessment of Factor V Activity in Apheresis Platelet Units: Implications for Management of FV Deficiency

Abstract Introduction Factor V (FV) deficiency is a rare but significant disorder associated with potentially life-threatening bleeding. Management may involve plasma infusion to increase FV activity. Although the majority (~80%) of FV is present in the plasma, approximately 20% is stored in platelet (PLT) alpha granules. As such, allogeneic PLT infusion is another strategy that has been proposed in the literature to raise FV levels. Although the rationale for this approach is understandable, these recommendations are based largely on anecdotal reports. Since FV is the most labile coagulation factor from an in vitro standpoint and given that allogeneic PLTs are stored at room temperature for 5–7 days after collection, we hypothesized that there would be low FV activity in PLT units and tested our hypothesis by assessing FV levels across PLT products. Material and Methods PLTs were aliquoted from apheresis units only, including those with PLT additive solution (PAS) and from non-PAS units (N=26) on post-collection days 3–6. Supernatant was prepared from PLTS by centrifugation (5000 rpm X 5 min) and was stored at -80oC until analyzed. PLT lysate (PL) was prepared by freezing (-80oC) then thawing (370 C) followed by centrifugation (10,000 rpm X 10 min). FV activity was tested in the PLT unit supernatant and lysate using a clinical-grade assay based on prothrombin time correction of FV deficient plasma and expressed as percent activity; reference range for normal plasma FV levels at our facility is 50–150% activity. Statistical analysis was performed using student t test. The data were expressed as mean ± SD (P-value <0.05 considered significant). Results FV activity was markedly low in PAS PLT units, in both supernatant (3.70% ± 1.02%) as well as PL (3.26% ± 1.02%); N=16. FV activity in non-PAS PLT units (N= 10) was also somewhat low relative to reference range plasma levels in both supernatant (44.55% ± 6.46%) and PL (39.67% ± 6.33%); however, it was significantly higher (P < .001) when compared to PAS PLT units. FV activity from aliquots extracted from the same PAS PLT units and examined serially over storage time (N=3) showed FV levels on day 3 of storage (supernatant 5.03% ± 1.41%; PL: 3.89% ± 1.03%) to be not significantly different than levels measured on day 5 of storage (supernatant: 3.10% ± 0.57%; PL: 2.61% ± 0.41%; P=0.4). Conclusion FV is substantially depleted across PLT components, with particularly low levels observed in PAS PLTs. Given comparable supernatant and PL FV levels, there appears to be little FV reserve available in PLT lysate. Based on these data, plasma should be considered a first-line therapy for most non-complex FV deficiency-associated bleeds. If PLTs are considered for additional use, then non-PAS PLT units should be preferentially employed.

High-Volume Platelet Distribution: Who Makes the Clinical Decision?

Abstract Anecdotally, many clinicians expect blood components to arrive in standard volumes. Blood components do not come in uniform sizes, however, and institutional experience has revealed platelet units to vary considerably in volume. Since many clinicians are not the ones examining blood products and their volumes prior to transfusion, there is a potential to transfuse a high-volume unit inadvertently to a patient at risk of transfusion-associated fluid overload (TACO), a leading cause of transfusion-related fatalities. The intent of this study was to examine the allocation practices of high-volume platelet units at an academic medical center. Over a six-month period, blood bank technical staff prospectively logged the allocation of high-volume apheresis platelet units with volumes greater than or equal to 400 mL. The staff member who issued the product logged the reason(s), if any, why he or she selected the unit for a particular patient when more than one ABO type-specific product was available. No patient identifiers or data were logged or analyzed in this study. Eighty-seven high-volume platelet units were recorded during the study period. The volumes ranged from 395 to 872 mL, with an average and standard deviation of 571 mL and 92 mL, respectively. Blood bank staff listed the following reasons for their allocation of high-volume platelet unit as follows: the product expiration date in 23 cases (26%), patient age in 13 cases (15%), patient sex in 12 cases (14%), and intraoperative use in 10 cases (11%). This study enumerated the variability in platelet unit volume, with some units containing likely double or triple the volume of the ordering clinicians expectations. Blood bank technologists made clinical decisions in the allocation of high-volume units in three-quarters of the documented cases. This underscores a need to provide clearly-defined guidelines for allocating such units, as well as a mechanism for clinicians to request lower-volume units, particularly for patients at risk of TACO.

Platelet transfusion: The effects of a fluid warmer on platelet function.

Thirty-one units of hospital blood bank apheresis PLTs were obtained. PLT-rich plasma (PRP) aggregometry and thromboelastography (TEG) were performed on the unit samples before and after the units were infused through a Ranger blood/fluid warming device. There were no differences in any of the aggregometry results before and after infusion of the PLTs through the blood warmer (all P > .32). There was a significant reduction in the TEG maximum amplitude (MA) of 69.8 ± 7.9 mm before and 66.0 ± 8.8 mm after (P < .001) infusion of the PLTs through the blood warmer and α angle 61.8 ± 9.4° before and 59.3 ± 8.2° after (P = .044) infusion of the PLTs through the blood warmer, although both mean values were within normal range for the TEG and not clinically significant. There were very good correlations of aggregometry and TEG results before and after infusion of the PLTs through the blood warmer device. This study did not demonstrate significant deleterious effect on PLT function from infusing apheresis PLT units through a blood warming device by PRP aggregometry. We did detect a statistically significant-but not clinically significant-reduction in TEG MA and α angle. The prohibition of transfusing PLT units though the Ranger blood warming device is not indicated.

Expansion of hospital-based blood collections in the face of COVID-19 associated national blood shortage.

BACKGROUNDWhen the coronavirus pandemic caused widespread school and business closures in March 2020, blood drives were canceled and the supply of blood decreased suddenly in the United States (US). In response, hospital‐based transfusion medicine physicians instituted policies to conserve blood and decrease blood product usage. These efforts were aided by the US Surgeon General recommendation to cancel all elective procedures. Nevertheless, the duration, severity, and impact of the pandemic on the national blood supply was uncertain. Hospitals with in‐house donor programs had the opportunity not only to control demand, but also increase supply.STUDY DESIGN AND METHODSA hospital‐based blood donor center was rapidly mobilized to increase the supply of in‐house collected blood, in order to counteract a sudden but potentially long‐term depletion of the national blood supply during a pandemic.RESULTSCollections increased approximately five‐fold above baseline for whole blood units, while apheresis platelet units were maintained at the historical average for the blood donor center. Cancellation of elective procedures showed a modest, but not yet statistically significant decrease in average blood product usage per day, nevertheless the in‐house collection rate was sufficient to meet demand.CONCLUSIONA hospital‐based blood donor center can quickly increase collection volumes and capacity in the face of a national emergency or pandemic. The desire to collect units should be balanced with safety concerns, need for sustainability, and blood product demand.

Comparison of abo antibody levels in apheresis platelets suspended in platelet additive solution and plasma.

BackgroundTransfusion of platelets (PLTs) with high ABO antibody titres can pose a risk of hemolysis if the unit crosses the ABO type. The PLTs stored in the platelet additive solution (PAS) remove asubstantial fraction of plasma and replace it with an isotonicbuffered solution.We aimed to assess the difference in anti-A/B antibody levels in Groups O, A and B apheresis platelets (APs) suspended in plasma and PAS.MethodologyApheresis donors are categorized into two groups, Plasma (Group I) and PAS (Group II), each blood group (A, B and O) had 20 samples. The anti-A/B(IgM)antibody levels were recorded from the AP donor (Group II) and from the AP units for both groups. The reduction in the anti-A/B(IgM) antibody levels in the APs suspended in the PAS for each blood group was determined.ResultsThe median anti-A titres in blood Groups B (p = 0.009) and O (p = 0.005) was significantly lower in Group II. However, the difference in anti-B levels was not significant in the blood groups A (p = 0.057) and O (p = 0.205). The median level of reduction in IgM antibody titres across donor samples and the PAS-stored platelets was two-fold. The regression showed a level of reduction in antibody titres which can be explained by baseline donor antibody titres in blood groups A and B compared to blood group O.ConclusionThe medianABO antibody titres were lower in APs suspended in PAS than in plasma. Addition of the PAS significantly lowered the IgM antibody titres by twofold, compared to plasma.

Supplemental findings of the 2017 National Blood Collection and Utilization Survey.

This report provides supplemental results from the 2017 National Blood Collection and Utilization Survey on characteristics of the donor population, autologous and directed donations and transfusions, platelets, plasma and granulocyte transfusions, pediatric transfusions, severe donor-related adverse events, cost of blood units, hospitals policies and practices, and inventory, dosing, and supply. Weighting and imputation were used to generate national estimates including number of donors, donations, donor deferrals, autologous and directed donations and transfusions, severe donor-related adverse events, platelet and plasma collections and transfusions, number of cross-match procedures, irradiation and leukoreduction, and pediatric transfusions. Between 2015 and 2017, successful donations decreased slightly by 2.1% with a 10.3% decrease in donations by persons aged 16-18 years and a 14.4% increase in donations by donors aged >65 years. The median price paid for blood components by hospitals decreased from $211 to $207 for leukoreduced red blood cell units, from $523 to $517 for leukoreduced apheresis platelet units, and from $54 to $51 for fresh frozen plasma units. Plasma transfusions decreased 13.6%, but group AB plasma units transfused increased 24.7%. Between 2015 and 2017, blood donations declined slightly because of decreases in donations from younger donors, but the number of donations from older donors increased. The price hospitals pay for blood has continued to decrease. Plasma transfusions have decreased, but the proportion of plasma transfusions involving group AB plasma have increased.

Inactivation of yellow fever virus with amotosalen and ultraviolet A light pathogen-reduction technology.

BACKGROUNDThe reemergence of yellow fever virus (YFV) in Africa and Brazil, and massive vaccine campaigns triggered to contain the outbreaks, have raised concerns over blood transfusion safety and availability with increased risk of YFV transfusion‐transmitted infections (TTIs) by native and vaccine‐acquired YFV. Blood donor deferral for 2 to 4 weeks following live attenuated YFV vaccination, and deferral for travel to endemic/epidemic areas, may result in blood donor loss and impact platelet component (PC) stocks. This study investigated the efficacy of INTERCEPT Blood System pathogen reduction (PR) with use of amotosalen and ultraviolet A (UVA) light to inactivate high levels of YFV in PCs.MATERIALSFour units of apheresis platelets prepared in 35% plasma/65% platelet additive solution (PC‐PAS) and 4 units of PC in 100% human plasma (PC‐Plasma) were spiked with high infectious titers of YFV (YFV‐17D vaccine strain). YFV‐17D infectious titers were measured by plaque assay and expressed as plaque‐forming units (PFU) before and after amotosalen/UVA treatment to determine log reduction.RESULTSThe mean YFV‐17D infectious titers in PC before inactivation were 5.5 ± 0.1 log PFU/mL in PC‐PAS and 5.3 ± 0.1 log PFU/mL in PC‐Plasma. No infectivity was detected immediately after amotosalen/UVA treatment.CONCLUSIONThe amotosalen/UVA PR system inactivated high titers of infectious YFV‐17D in PC. This PR technology could reduce the risk of YFV TTI and help secure PC supplies in areas experiencing YFV outbreaks where massive vaccination campaigns are required.

Evaluation of Efficacy and Safety of Cold-Stored Platelets in Healthy Human Subjects Treated with Dual Antiplatelet Therapy

Background: Platelets are currently stored at 22°C (room temperature-stored) for clinical purposes. This approach has numerous downsides including limited storage time due to risk of bacterial growth, and increased costs caused by bacterial testing or pathogen reduction. Platelets stored at 4ºC (cold-stored) were the standard of care in the 1960s and 70s, and while they generally perform better than room temperature-stored platelets in in vitro assays, functional studies in vivo have yielded contradictory results. Methods: Eight healthy human participants were included in the analysis of this randomized, cross-over study. A double unit of apheresis platelets was collected from each subject for autologous transfusion. Platelets were stored for 5 days at either 4ºC, or 22ºC, based on randomization. On day 5, platelets were transfused 12-24 hours after participants received a loading dose of acetylsalicylic acid and clopidogrel. An array of platelet function testing was done at baseline, after loading dose, and after transfusion (1h, 4h, 24h). The first round was followed by a wash-out period of at least 10 days, and a second sequence of collection, antiplatelet loading dose, and transfusion with platelets stored under alternate conditions from the first sequence. The primary endpoint was defined as post-transfusion platelet αIIbβ3 integrin activation in response to agonists for pathways inhibited by dual antiplatelet therapy, measured by the VerifyNOW assay. Secondary endpoints included platelet function testing by bleeding time, VASP-phosphorylation, light transmission aggregometry, and flow cytometric analysis of platelet αIIbβ3 integrin activation and α-granule secretion. Results: All cold-stored platelet units passed quality control analyses, and no platelet aggregates were observed at the end of the storage period. One room temperature-stored unit had to be discarded due to quality control failure. Transfusion of a double unit with 5 day cold-stored platelets was tolerated well by all recipients. The absolute number of transfused platelets did not differ significantly between the cold-storage arm and the room temperature storage arm. The corrected count increment did not differ significantly at 1h after transfusion, but was significantly lower in the cold-stored group at the 4h, and 24h time points. The primary endpoint, platelet function testing by VerifyNOW, showed reversal of the effect of acetylsalicylic acid with both products at 1h and 4h post transfusion, but platelet inhibition re-appeared after 24h post transfusion in the cold-storage arm, presumably due to accelerated clearance of cold-stored platelets. No significant differences were observed between the two products in the VerifyNOW assay for clopidogrel. The bleeding time (a secondary endpoint) did not differ significantly at any time point between the cold-stored and room temperature-stored transfusion group. However, the bleeding time improved or remained unchanged in all recipients transfused with room temperature-stored platelets, whereas, transfusion of cold-stored platelets caused prolongation of the bleeding time in 50% of recipients. Surprisingly, platelets isolated from recipients of room temperature-stored platelets aggregated significantly better in response to collagen compared to platelets isolated from recipients of cold-stored platelets at 1h and 4h post transfusion. Other secondary endpoints, including VASP-phosphorylation, αIIbβ3 integrin activation and α-granule secretion by flow cytometry, and platelet aggregation in response to arachidonic acid and ADP did not differ significantly between the two treatment groups. Conclusion: We report the first safety and efficacy data of 5 day cold stored platelets in plasma. Unexpectedly, some endpoints demonstrate agonist- and assay-dependent inferiority of cold-stored platelets at early and late time points. Further studies are needed to determine the maximum storage time, and the efficacy of cold-stored platelets in actively bleeding patients and patients with platelet dysfunction. Disclosures No relevant conflicts of interest to declare.

Amotosalen and ultraviolet A light efficiently inactivate MERS-coronavirus in human platelet concentrates.

SUMMARYObjectiveThis study aimed to assess the efficacy of the INTERCEPT™ Blood System [amotosalen/ultraviolet A (UVA) light] to reduce the risk of Middle East respiratory syndrome‐Coronavirus (MERS‐CoV) transmission by human platelet concentrates.BackgroundSince 2012, more than 2425 MERS‐CoV human cases have been reported in 27 countries. The infection causes acute respiratory disease, which was responsible for 838 deaths in these countries, mainly in Saudi Arabia. Viral genomic RNA was detected in whole blood, serum and plasma of infected patients, raising concerns of the safety of blood supplies, especially in endemic areas.MethodsFour apheresis platelet units in 100% plasma were inoculated with a clinical MERS‐CoV isolate. Spiked units were then treated with amotosalen/UVA to inactivate MERS‐CoV. Infectious and genomic viral titres were quantified by plaque assay and quantitative real‐time reverse transcription polymerase chain reaction (RT‐qPCR). Inactivated samples were successively passaged thrice on Vero E6 cells to exclude the presence of residual replication‐competent viral particles in inactivated platelets.ResultsComplete inactivation of MERS‐CoV in spiked platelet units was achieved by treatment with Amotosalen/UVA light with a mean log reduction of 4·48 ± 0·3. Passaging of the inactivated samples in Vero E6 showed no viral replication even after nine days of incubation and three passages. Viral genomic RNA titration in inactivated samples showed titres comparable to those in pre‐treatment samples.ConclusionAmotosalen and UVA light treatment of MERS‐CoV‐spiked platelet concentrates efficiently and completely inactivated MERS‐CoV infectivity (>4 logs), suggesting that such treatment could minimise the risk of transfusion‐related MERS‐CoV transmission.

Desmopressin is a transfusion sparing option to reverse platelet dysfunction in patients with severe traumatic brain injury.

Platelet dysfunction (PD) is an independent predictor of mortality in patients with severe traumatic brain injury (sTBI). Platelet transfusions (PLTs) have been shown to be an effective treatment strategy to reverse platelet inhibition. Their use is contingent on availability and may be associated with increased cost and transfusion-related complications, making desmopressin (DDAVP) attractive. We hypothesized that DDAVP would correct PD similarly to PLTs in patients with sTBI. This retrospective study evaluated all blunt trauma patients admitted to an urban, level 1 trauma center from July 2015 to October 2016 with sTBI (defined as head abbreviated injury scale [AIS] ≥3) and PD (defined as adenosine diphosphate [ADP] inhibition ≥60% on thromboelastography) and subsequently received treatment. Per our institutional practice, patients with sTBI and PD are transfused one unit of apheresis platelets to reverse inhibition. During a platelet shortage, we interchanged DDAVP for the initial treatment. Patients were classified as receiving DDAVP or PLT based on the initial treatment. A total of 57 patients were included (DDAVP, n = 23; PLT, n = 34). Patients who received DDAVP were more severely injured (injury severity score, 29 vs. 23; p = 0.045), but there was no difference in head AIS (4 vs. 4, p = 0.16). There was no difference between the two groups in admission platelet count (244 ± 68 × 10/μL vs. 265 ± 66 × 10/μL, p = 0.24) or other coagulation parameters such as prothrombin time, partial thromboplastin time, or international normalized ratio. Before treatment, both groups had similar ADP inhibition as measured by thromboelastography (ADP, 86% vs. 89%, p = 0.34). After treatment, both the DDAVP and PLT groups had similar correction of platelet ADP inhibition (p = 0.28). In patients with severe traumatic brain injury and PD, DDAVP may be an alternative to PLTs to correct PD. Therapeutic, level IV.

RBC and Platelet Transfusion Requirements in the First 30 Days after Allogeneic Hemopoietic Cell Transplantation and Transfusion Independence: A Single Center Retrospective Study of 1803 Recipients

Background Allogeneic hematopoietic cell transplant (allo-HCT) recipients often require substantial but variable transfusion support. Few studies have quantified their transfusion burden, or identified prognostic factors for increased transfusions to guide patient counseling or inventory management. Data on haploidentical HCT (Haplo-HCT) patients are especially scarce. Objectives To identify factors associated with increased RBC and platelet (PLT) transfusions, and provide for the first time data on a large cohort of Haplo-HCT patients. Methods We retrospectively evaluated 1803 consecutive first time adult allo-HCT patients transplanted at our center in 2011-17. Multivariate linear regression and Fine-Gray subdistribution hazards models were used to examine the associations between baseline characteristics (age, sex, disease stage, graft type, donor type, ABO compatibility and conditioning regimen) and log-transformed transfusion units in the first 30 days after HCT and time to reach transfusion independence respectively. Results The median age of the cohort was 53(18-78); 56.2% were male. Most common diagnoses were AML (38.8%), ALL (19.6%), and lymphoma (14.8%); 50.2% had advanced disease. Patients received nonmyeloablative/reduced intensity (58.9%) or myeloablative conditioning regimens (MAC, 41.1%), followed by peripheral blood stem cell (88.4%), bone marrow (6.9%) or umbilical (UC, 4.7%) HCT. Most grafts were from matched related (MRD, 38.7%) or unrelated (MUD, 49.1%) donors, and 7.6% were haploidentical. ABO incompatibility (Major 15.8%, minor 18.6%, bi-directional 8.5%) was present in 42.9% of the cases (Table 1). Most of the 1764 patients who survived 30+ days received RBC (88.2%) or PLT (97.2%) transfusions during the first 30 days, with a median of 3 (0-37) RBC and 5(0-144) apheresis PLT units. RBC and PLT transfusion independence was reached in 28 (95%CI: 26-31) and 12 (95%CI: 12-13) days respectively. Multivariate analyses showed that Haplo-HCT and UC graft were independently associated with more RBC and PLT transfusions, as were advanced disease, ABO incompatibility, older age, and MAC (P Conclusions We identified patient and transplant factors strongly associated with increased transfusions in the first 30 days after allo-HCT, and quantified the transfusion burden of Haplo-HCT relative to other types of HCT.

Seasonal variability is not observed in the rates of high anti-A and anti-B titers in plasma, apheresis platelet, and whole blood units tested by different methods.

ABO-incompatible platelet transfusions are common, and transfusions with ABO-incompatible plasma are increasing with the use of group A plasma and group O whole blood (WB) in emergencies. Many centers screen blood products for anti-A and/or anti-B titers to help prevent hemolysis from ABO-incompatible transfusions, yet titer methods and definition of high titers are not standardized. This international multicenter study collected data on anti-A and anti-B titer practices for plasma, apheresis platelet (AP), and WB units from January 2015 through December 2017 to determine the prevalence of high-titer units using local definitions. A total of 87,701 plasma, AP and WB units were screened for high-titer anti-A and/or anti-B. High-titer detection rates for group A plasma ranged 0%-13.6%; group A AP 2.7%-9.3%; group O AP 2.3%-65.7%; and group O WB 6.4%-20.7%. At the one center that collected group B AP, the high-titer rate was 10.9%. High-titer rates varied from month to month, as well as between years for a given month. There was no clear pattern of when high-titer units were donated. The prevalence of high-titer plasma, AP, and WB units varies by titer method and local definition of high titer. Even at the lowest titer threshold of 50, a significant proportion of units had a high-titer antibody, although the clinical relevance of this finding needs further investigation.

Platelet-Derived Microvesicles Reverse the Lupus Anticoagulant Effect and Are More Potent then Synthetic Phospholipids in Supporting Thrombin Generation in Antiphospholipid Syndrome

Background:Antiphospholipid Syndrome (APS) is associated with clinical thrombosis manifestations. However, it is characterized as prolongation of lag time in phospholipid (PL) dependent laboratory coagulation assays, a reflection of the paradoxical lupus anticoagulant (LAC) effect. In contrast to clinical laboratory testing which almost exclusively utilize synthetic PL (sPL), activated platelets are a major source for PL for in vivo hemostasis. It was recently reported that platelet-derived microvesicles (P-MVs) release is mediated by a positive thrombin generation feedback loop in the process of platelet activation and membrane ballooning, which supports a physiological role for P-MVs in hemostasis (Agbani, et. al., 2017).Objective: To evaluate and compare thrombin generation (TG) supported by P-MVs, Erythroid MVs (E-MVs) and sPL in normal subjects and APS patients.Methods: MVs were prepared by gentle sonication or hypotonic-mechanical disruption of washed whole blood platelet pellets, platelet apheresis units or red blood units; sPL composition used was PS/PE/PC=20/20/60 (Bloemen, et. al., 2017). Particle size distribution and anionic phosphatidylserine (PS) expression on P-MV, E-MVs and sPL by Annexin 5-Oregan green (A5-OG) staining were analyzed by flow cytometry using Apogee A60-Micro Plus. TG measured by calibrated automated thrombinography (CAT) was used to evaluate a procoagulable capacity of sPL, P-MVs, and E-MVs after initiating with tissue factor (TF).Results: P-MVs and sPL were equivalent as a source of PL in supporting TG in normal platelet poor plasmas. TG in pooled normal plasma (PNP) in the presence of 1 pM TF showed that P-MVs in dose-dependent fashion support thrombin generation to a similar degree as standard sPLs dilutions including a dose of 4 µM, validated earlier as a saturated concentration in CAT assay (Gerotziafas GT, et. al., 2005). Increasing concentration of either P-MVs or sPLs had little effect on lag time in PNP. In APS patient plasma, lag time was dose-dependently shortened with P-MVs, from 20 minutes to less than 10 minutes, and peak height was dose-dependently increased to a nearly normal level with the highest P-MVs tested. When sPLs was used, TG more severely affected. Strong thrombin generation occurred only with high concentration sPLs (32 µM) after more than 20 min lag time (Figure 1B). E-MVs showed a similar pattern in generating thrombin as sPL in normal plasma and in APS patient with prolonged lag time. The reversal of LAC phenomenon with correction of lag time in APS patients with P-MVs in TG CAT assay was confirmed by testing another 6 (out of 10) APS patients. Microvesicles size, analyzed on A60-Micro Plus, using large angle light scatter (LALS) demonstrated that all three types of MV were consistently less than 1micrometer in diameter. E-MVs and sPL had a similar size distribution, and the majority were of a diameter comparable to 110nm polystyrene calibration beads. P-MVs had wider distribution ranging up to 500nm. All three types of vesicles showed a PS expression by A5-OG labeling with 88.8%, 69.3% and 43.9% MV positivity for sPL, P-MVs and E-MVs, respectively and equivalent mean fluorescent intensity.Summary: Platelet-derived microvesicles significantly promoted thrombin generation in APS patients. This is a revisiting of the “platelet neutralization effect” that was observed nearly 4 decades ago (Thiagarajan P, et. al., 1980). Our data demonstrate that P-MVs consistently increased TG in APS patient plasma compared to equivalent doses of sPL despite similar level of PS expression. In conclusion, cell-derived membranes from different source expressing PS might have different mechanisms to facilitate assembly of coagulation enzyme-substrate-cofactor complexes with resulting enzymatic activity than sPL and help explain LAC phenomenon. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Human T-cell lymphotropic virus: A simulation model to estimate residual risk with universal leucoreduction and testing strategies in Canada.

In Canada, transfusion transmission risk of Human T-cell lymphotropic virus -I/II (HTLV) is addressed by universal leucoreduction and universal antibody testing. We aimed to estimate the risk with the current policy, if testing only first-time donors and if testing were stopped. Monte Carlo simulation was employed to estimate the proportion of red cell concentrate, random donor platelet and apheresis platelet units that would be released into inventory in each scenario (10 billion donors each). The model estimated the number of HTLV-positive donations not intercepted by testing, randomly assigned the number of HTLV particles/100 leucocytes using proportions from published data and randomly selected a postleucoreduction leucocyte count from quality control data. Units were considered infectious if ≥9×104 copies of HTLV provirus. With universal leucoreduction in place, the residual risk of releasing an HTLV potentially infectious unit with universal testing was 1 in 1·2 billion units (0, 1 in 55·9 million), with testing only first-time donors 1 in 7·1 million (0, 1 in 1·05 million) and with no testing 1 in 1·0 million (0, 1 in 178600). The efficacy of leucoreduction was >99·5% (lower bound 95·7%) for all scenarios. With universal leucoreduction in place, switching from universal testing to testing first-time donors would incur very low risk.

Visualization of bacterial contamination in an apheresis platelet unit.

Visualization of bacterial contamination in an apheresis platelet unit.

The effects of storage on platelet function in different blood products

ABSTRACTObjectives: Reduced platelet (PLT) function during storage has been shown for buffy-coat-derived platelet concentrates (BCP) and apheresis platelet units (AP), while for whole blood (WB) it has not been well studied. The aim of this study was to investigate PLT function in these blood products throughout storage using a novel flow cytometric assay.Methods: Flow cytometric measurement of agonist-induced platelet aggregation, CD62P expression and PAC-1 binding during storage in BCP, AP (1–9 days at 20°C) and WB (1–21 days at 2–6°C).Results: PLT-aggregation capacity decreased from day 1 to day 7 for almost all product–agonist combinations (P = .004 to P = .029) with aggregation capacity of WB being similar to that of AP and BCP. WB aggregation capacity remained relatively unchanged from day 7 to day 21. For all blood products, the fraction of agonist-induced CD62P-expression remained high and the fraction of PAC-1 binding decreased during storage. WB PLTs underwent only small changes in CD62P expression and PAC-1 binding from day 7 to day 21.Conclusion: This study found PLT aggregation in WB stored at 4°C to be as least as good as for BCP and AP stored at 20°C. WB retained significant PLT-aggregation capacity to day 21.

Systems analysis of metabolism in platelet concentrates during storage in platelet additive solution.

Platelets (PLTs) deteriorate over time when stored within blood banks through a biological process known as PLT storage lesion (PSL). Here, we describe the refinement of the biochemical model of PLT metabolism, iAT-PLT-636, and its application to describe and investigate changes in metabolism during PLT storage. Changes in extracellular acetate and citrate were measured in buffy coat and apheresis PLT units over 10 days of storage in the PLT additive solution T-Sol. Metabolic network analysis of these data was performed alongside our prior metabolomics data to describe the metabolism of fresh (days 1-3), intermediate (days 4-6), and expired (days 7-10) PLTs. Changes in metabolism were studied by comparing metabolic model flux predictions of iAT-PLT-636 between stages and between collection methods. Extracellular acetate and glucose contribute most to central carbon metabolism in PLTs. The anticoagulant citrate is metabolized in apheresis-stored PLTs and is converted into aconitate and, to a lesser degree, malate. The consumption of nutrients changes during storage and reflects altered PLT activation profiles following their collection. Irrespective of the collection method, a slowdown in oxidative phosphorylation takes place, consistent with mitochondrial dysfunction during PSL. Finally, the main contributors to intracellular ammonium and NADPH are highlighted. Future optimization of flux through these pathways provides opportunities to address intracellular pH changes and reactive oxygen species, which are both of importance to PSL. The metabolic models provide descriptions of PLT metabolism at steady state and represent a platform for future PLT metabolic research.

Routine use of Day6 and Day7 platelets with rapid testing: two hospitals assess impact 1year after implementation.

In March 2016 the US Food and Drug Administration published a draft guidance to enhance the safety of platelets (PLTs) for transfusion. Options for hospital transfusion services include the use of rapid testing to extend apheresis PLT dating for up to 7 days. This report describes the impact of routine use of Day 6 and Day 7 PLTs at two hospital transfusion services 1 year after implementation of rapid testing for outdate extension. PLT transfusion and inventory data were obtained from two hospital-based transfusion services for 12months before and 12months after implementation of rapid testing to extend the outdate of apheresis PLTs to 7 days. The outdate rate decreased from 5% to 2% (p<0.0001) at Hospital 1 and 28% to 14% (p<0.001) at Hospital 2 after implementation of routine use of Day 6 and Day 7 PLTs. The proportion of apheresis PLT units that underwent secondary screening for bacterial contamination before transfusion in the postimplementation period increased from 33% to 54% at Hospital 1 and from 0% to 31% at Hospital 2. A significant decrease in outdate rate was observed after routine use of Day 6 and Day 7 PLTs. Use of rapid testing to extend PLT outdate also resulted in a larger proportion of PLTs that underwent secondary testing for bacterial contamination before transfusion. These observations demonstrate that use of rapid testing to extend apheresis PLT dating up to 7 days enhances the safety of PLTs for transfusion and decreases wastage of a limited resource.