Reversibility of severe metabolic stress in stored platelets after in vitro plasma rescue or in vivo transfusion: restoration of secretory function and maintenance of platelet survival

Reduction of ristocetin-induced platelet aggregation (RIPA) during storage despite plasma renewal: evidence for hemostatic importance of GPIbα shedding

BACKGROUND

Platelet storage is complicated by deleterious changes, among which reduction of ristocetin-induced platelet aggregation (RIPA) has a poorly understood mechanism. The study elucidates the mechanistic roles of all the possible players in this process.

RESEARCH DESIGN AND METHODS

PRP-platelet concentrates were subjected to RIPA, collagen-induced platelet aggregation (CIPA), and flowcytometric analysis of GPIbα and PAC-1 binding from days 0 to 5 of storage. Platelet-poor plasma was subjected to colorimetric assays for glucose/LDH evaluation and automatic analyzer to examine VWF antigen and activity.

RESULTS

From day three of platelet storage, reducing CIPA but not RIPA was correlated with the reduction of both metabolic state and integrin activity. RIPA reduction was directly related to the decreased levels of total-content/expression of GPIbα, and inversely related to its shedding levels during storage. Re-suspension of 5-day stored platelet in fresh plasma compensated CIPA, but not RIPA. VWF concentration and its activity did not change during storage while they had no correlation with RIPA.

CONCLUSIONS

This study identified the irreversible loss of platelet GPIbα, but not VWF status, as the primary cause of the storage-dependent decrease of RIPA. Unlike CIPA, this observation was not compensated by plasma refreshment, suggesting that some evidence of PSL may not be recovered after transfusion.

Effects of a Single Rapid Infusion System on Platelet Function in Stored Whole Blood: An Ex Vivo Study

Introduction

Rapid infusion systems (RIS) are used to warm and rapidly infuse crystalloids and blood products. Current guidelines do not approve of platelet transfusion through a RIS, but data supporting these guidelines are scarce. Our hypothesis was that an infusion of whole blood through a RIS would degrade platelet quantity, impede viscoelastic clot strength, and inhibit platelet aggregation response to adenosine diphosphate pathway (ADP) activation.

Methods

Ten iterations of a simulated scenario of transfusing whole blood via a single brand and make of RIS (Belmont Fluid Management System 2000, Belmont Medical Technologies, Billerica, MA) were performed. Units of whole blood, which were two to nine days old, were leukoreduced prestorage. Blood was used to prime the RIS and then warmed and infused at 100 mL/min into a reservoir. Blood samples were collected before and immediately after infusion. Samples were tested for platelet count, size, and viscoelastic clot strength using thromboelastographic and aggregation assays.

Results

The study sample (n = 10) included platelets with an average age of 5.3 days. The infusion through the RIS had a detrimental effect on all the maximal amplitudes (MA) of viscoelastic testing: MA ADP (mean difference = −18.7 mm; 95% CI: −24.1 to −13.3, P = 0.004), MA rapid thromboelastography (MA rTEG) (mean difference = −6.0; 95% CI: −10.0 to −2.0, P = 0.008), MA TEG (mean difference = −7.1; 95% CI: −10.9 to −3.4, P = 0.004), mean platelet volume (MPV) (mean difference = −0.3; 95% CI: −0.6 to −0.1, P = 0.02), and platelet count (mean difference = −68.3 × 10³/µL; 95% CI: −86.9 to −49.7, P = 0.004).

Conclusions

Platelet quantity, viscoelastic clot strength, and platelet aggregation response to ADP each decline after infusion through a RIS. Further studies regarding microaggregates and platelet activation are required.

Human platelets labeled at two discrete biotin densities are functional in vitro and are detected in vivo in the murine circulation: A promising approach to monitor platelet survival in vivo in clinical research

BACKGROUND

The production of platelet concentrates (PCs) is evolving, and their survival capacity needs in vivo evaluation. This requires that the transfused platelets (PLTs) be distinguished from those of the recipient. Labeling at various biotin (Bio) densities allows one to concurrently trace multiple PLT populations, as reported for red blood cells.

STUDY DESIGN AND METHODS

A method is described to label human PLTs at two densities of Bio for future clinical trials. Injectable-grade PLTs were prepared in a sterile environment, using injectable-grade buffers and good manufacturing practices (GMP)-grade Sulfo-NHS-Biotin. Sulfo-NHS-Biotin concentrations were chosen to maintain PLT integrity and avoid potential alloimmunization while enabling the detection of circulating BioPLTs. The impact of biotinylation on human PLT recirculation was evaluated in vivo in a severe immunodeficient mouse model using ex vivo flow cytometry.

RESULTS

BioPLTs labeled with 1.2 or 10 μg/ml Sulfo-NHS-Biotin displayed normal ultrastructure and retained aggregation and secretion capacity and normal expression of the main surface glycoproteins. The procedure avoided detrimental PLT activation or apoptosis signals. Transfused human BioPLT populations could be distinguished from one another and from unlabeled circulating mouse PLTs, and their survival was comparable to that of unlabeled human PLTs in the mouse model.

CONCLUSIONS

Provided low Sulfo-NHS-Biotin concentrations (<10 μg/ml) are used, injectable-grade BioPLTs comply with safety regulations, conserve PLT integrity, and permit accurate in vivo detection. This alternative to radioisotopes, which allows one to follow different PLT populations in the same recipient, should be valuable when assessing new PC preparations and monitoring PLT survival in clinical research.

Platelet in vitro assays: their correspondence with their in vivo hemostatic potential

Developments during the past few years have resulted in multiple kinds of platelet products for transfusion. This involves different collection methods, containers, preservative solutions, modifications of storage temperatures and durations, and additional treatments such as pathogen reduction. Much experience has been obtained testing these processes in vitro to seek indications of in vivo effectiveness. Availability of an in vitro method that correlated with in vivo effectiveness would be extremely valuable for these different kinds of platelet products and as more innovation in platelet preparation occurs in the future. This report reviews the methods for in vitro platelet testing with a view to their in vivo implications and whether such testing could be helpful in projecting the clinical effectiveness of different platelet products.

Comparison of platelet function tests for the in vitro quality assessment of platelet concentrates produced under real-life conditions

Platelet quality in different platelet concentrates (PCs) has been the subject of several studies. Nonetheless, there is a lack of robust data on the correlation and agreement among platelet function tests as a prerequisite for the association of PC functionality in vitro with platelet function in vivo post PC transfusion. The purpose of our study was to correlate a larger panel of platelet function assays in PCs and to assess whether the methods agree sufficiently and can be used interchangeably. Twelve apheresis platelet concentrates in plasma (APC), 16 pooled platelet concentrates in plasma (PPC), and 12 PPC in T-sol (PPCA) were examined on days 1 and 4 after production. PCs were tested for platelet count, light transmission aggregation (LTA) induced by ADP, collagen, or TRAP; platelet ATP release induced by collagen; and spontaneous and ADP and TRAP-induced increase in CD62P and PAC1 expression measured by flow cytometry. All tests were performed in undiluted platelet-rich plasma, recalcified and mixed with an inhibitor of factor Xa and thrombin. Most platelet function parameters correlated significantly with each other, but agreement among methods was insufficient. A proper inverse correlation was observed between ADP-induced LTA and spontaneous platelet activation assessed by CD62P expression (r = -0.61, p < 0.0001). Spontaneous CD62P correlated also significantly with spontaneous PAC1 (r = 0.69, p < 0.0001) and inversely with TRAP-induced CD62P expression (r = -0.86, p < 0.0001). We found significant correlations among all flow cytometric assays measuring platelet CD62P and PAC1 expression induced by ADP or TRAP. Subsequent Bland Altman analysis revealed insufficient agreement between methods. With one exception (collagen-induced LTA compared with TRAP-induced LTA, percentage error = 16%) the limits of agreement expressed as percentage error exceeded the chosen acceptable difference of 30%. In APC, platelet count was 41% and 44% higher, respectively, than in PPC and PPCA (p < 0.0001). Spontaneous CD62P and PAC1 expression were significantly greater, and ADP-induced aggregation and agonist-induced increase in CD62P and PAC1 were significantly lower in PPCA compared to APC and PPC on day 4 of storage. ADP and TRAP-induced CD62P and PAC1 activatability fell significantly during storage between day 1 and day 4 in APC and PPCA, but not in PPC. In conclusion, different platelet function tests capture different aspects of platelet function and do not correlate and agree sufficiently to be used interchangeably.

Ultraviolet-Based Pathogen Inactivation Systems: Untangling the Molecular Targets Activated in Platelets

Transfusions of platelets are an important cornerstone of medicine; however, recipients may be subject to risk of adverse events associated with the potential transmission of pathogens, especially bacteria. Pathogen inactivation (PI) technologies based on ultraviolet illumination have been developed in the last decades to mitigate this risk. This review discusses studies of platelet concentrates treated with the current generation of PI technologies to assess their impact on quality, PI capacity, safety, and clinical efficacy. Improved safety seems to come with the cost of reduced platelet functionality, and hence transfusion efficacy. In order to understand these negative impacts in more detail, several molecular analyses have identified signaling pathways linked to platelet function that are altered by PI. Because some of these biochemical alterations are similar to those seen arising in the context of routine platelet storage lesion development occurring during blood bank storage, we lack a complete picture of the contribution of PI treatment to impaired platelet functionality. A model generated using data from currently available publications places the signaling protein kinase p38 as a central player regulating a variety of mechanisms triggered in platelets by PI systems.

Comparison of haemostatic function of PAS-C-platelets vs. plasma-platelets in reconstituted whole blood using impedance aggregometry and thromboelastography

BACKGROUND AND OBJECTIVES

There are concerns about the haemostatic function of platelets stored in platelet additive solution (PAS). Aim of this study was to compare the haemostatic function of PAS-C-platelets to plasma-platelets in reconstituted whole blood.

MATERIALS AND METHODS

In our experiment, whole blood was reconstituted with red blood cells, solvent-detergent (SD) plasma and either PAS-C-platelets or plasma-platelets (n = 7) in a physiological ratio. On storage days 2, 5, 8 and 13, the agonist-induced aggregation (multiple electrode aggregometry), clot formation (thromboelastography) and agonist-induced CD62P responsiveness (flow cytometry) were measured.

RESULTS

Samples with PAS-C-platelets showed significantly lower aggregation than plasma-platelets when induced with adenosine diphosphate, -6 U (95% confidence interval: -8; -4) or thrombin receptor-activating protein, -15 U (-19; -10). Also when activated with collagen and ristocetin, the PAS-C-platelets showed less aggregation, although not statistically significant. All samples with PAS-C-platelets showed significantly lower agonist-induced CD62P responsiveness than samples with plasma-platelets. However, there was no difference regarding all TEG parameters.

CONCLUSION

Our findings demonstrate that the function - aggregation and CD62P responsiveness - of PAS-C-platelets in reconstituted whole blood is inferior to that of plasma-platelets, which may have implications in the setting of massive transfusions.

Acid sphingomyelinase mediates murine acute lung injury following transfusion of aged platelets

Pulmonary complications from stored blood products are the leading cause of mortality related to transfusion. Transfusion-related acute lung injury is mediated by antibodies or bioactive mediators, yet underlying mechanisms are incompletely understood. Sphingolipids such as ceramide regulate lung injury, and their composition changes as a function of time in stored blood. Here, we tested the hypothesis that aged platelets may induce lung injury via a sphingolipid-mediated mechanism. To assess this hypothesis, a two-hit mouse model was devised. Recipient mice were treated with 2 mg/kg intraperitoneal lipopolysaccharide (priming) 2 h before transfusion of 10 ml/kg stored (1–5 days) platelets treated with or without addition of acid sphingomyelinase inhibitor ARC39 or platelets from acid sphingomyelinase-deficient mice, which both reduce ceramide formation. Transfused mice were examined for signs of pulmonary neutrophil accumulation, endothelial barrier dysfunction, and histological evidence of lung injury. Sphingolipid profiles in stored platelets were analyzed by mass spectrophotometry. Transfusion of aged platelets into primed mice induced characteristic features of lung injury, which increased in severity as a function of storage time. Ceramide accumulated in platelets during storage, but this was attenuated by ARC39 or in acid sphingomyelinase-deficient platelets. Compared with wild-type platelets, transfusion of ARC39-treated or acid sphingomyelinase-deficient aged platelets alleviated lung injury. Aged platelets elicit lung injury in primed recipient mice, which can be alleviated by pharmacological inhibition or genetic deletion of acid sphingomyelinase. Interventions targeting sphingolipid formation represent a promising strategy to increase the safety and longevity of stored blood products.

Aging of platelets stored for transfusion

A goal of platelet storage is to maintain the quality of platelets from the point of donation to the point of transfusion - to suspend the aging process. This effort is judged by clinical and laboratory measures with varying degrees of success. Recent work gives encouragement that platelets can be maintained ex vivo beyond the current 5 -7 day shelf life whilst maintaining their quality, as measured by posttransfusion recovery and survival. However, additional measures are needed to validate the development of technologies that may further reduce the aging of stored platelets, or enhance their hemostatic properties.

Functional recovery of stored platelets after transfusion

BACKGROUND

Platelet (PLT) concentrates are prophylactically given to prevent major bleeding complications. The corrected count increment (CCI) is currently the only tool to monitor PLT transfusion efficacy. PLT function tests cannot be performed in patients with thrombocytopenia. Therefore, an optimized agonist-induced assay was used to determine PLT function, in patients with severe thrombocytopenia before and after transfusion.

STUDY DESIGN AND METHODS

PLT reactivity toward adenosine diphosphate (ADP), thrombin receptor-activating peptide SFLLRN (TRAP), and convulxin (CVX) was assessed by flow cytometry. P-selectin expression was measured on PLTs from 11 patients with thrombocytopenia before and 1 hour after transfusion, on stored PLTs, and on stored PLTs incubated for 1 hour in whole blood from patients ex vivo.

RESULTS

The mean (±SEM) CCI after 1 hour was 11.4 (±1.5). After transfusion, maximal agonist-induced PLT P-selectin expression was on average 29% higher for ADP (p = 0.02), 25% higher for TRAP (p = 0.007), and 24% higher for CVX (p = 0.0008). ADP-induced reactivity of stored PLTs increased with 46% after ex vivo incubation (p = 0.007). These PLTs also showed an overall higher P-selectin expression compared to PLTs 1 hour after transfusion (p = 0.005). After normalization for this background expression, a similar responsiveness was observed.

CONCLUSIONS

Our study shows recovery of PLT function after transfusion in patients with thrombocytopenia. The majority of functional PLTs measured after transfusion most likely represents stored transfused PLTs that regained functionality in vivo. The difference in baseline P-selectin expression in vivo versus ex vivo suggests a rapid clearance from circulation of PLTs with increased P-selectin expression.

Resveratrol preserves the function of human platelets stored for transfusion

Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for 5 d released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol's beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function.

Automated cold temperature cycling improves in vitro platelet properties and in vivo recovery in a mouse model compared to continuous cold storage

BACKGROUND

Platelets (PLTs) stored at cold temperatures (CTs) for prolonged time have dramatically reduced bacterial growth but poor survival when infused. A previous study demonstrated that human PLTs stored with manual cycling between 4 °C (12 hr) and 37 °C (30 min) and infused into severe combined immunodeficient (SCID) mice had survivals similar to or greater than those stored at room temperature (RT). In this study, the in vitro and in vivo properties of PLTs stored in an automated incubator programmed to cycle between 5 °C (11 hr) and 37 °C (1 hr) were evaluated.

STUDY DESIGN AND METHODS

A Trima apheresis unit (n = 12) was aliquoted (60 mL) in CLX bags. One sample was stored with continuous agitation (RT), a second sample was stored at 4-6 °C without agitation (CT), and a third sample was placed in an automated temperature cycler with 5 minutes of agitation during the warm-up period (thermocycling [TC]). PLTs were assayed for several relevant quality variables. On Day 7, PLTs were infused into SCID mice and in vivo recovery was assessed at predetermined time points after transfusion.

RESULTS

The glucose consumption rate, morphology score, hypotonic shock recovery level, and aggregation levels were increased and mitochondrial reactive oxygen species accumulations were decreased in TC-PLTs compared to those of CT-PLTs. The pH and Annexin V binding were comparable to those of RT-PLTs. All TC-PLTs had greater recovery than CT-PLTs and were comparable to RT-PLTs.

CONCLUSION

PLTs stored under automated TC conditions have improved in vivo recovery and improved results for a number of in vitro measures compared to CT-PLTs.

Evaluation of store lesion in platelet obtained by apheresis compared to platelet derived from whole blood and its impact on the in vitro functionality

Platelet units for transfusion purposes are obtained manually from whole blood or by apheresis, in an automated process. In both methods, platelets during storage present a characteristics grouped under the name "storage lesion" that are associated with adverse effects on platelet units. Oxidative stress has been claimed to be one of major causes, leading to activation and apoptosis processes affecting their post transfusion functionality. In this work, we observed an association between apheresis and a reduced presence of oxidative stress and better results in functional markers in stored platelets, compared to manually obtained platelets. Then, apheresis which would ensure a greater number of functional platelets during the 5 days of storage, compared to concentrates obtained from whole blood.

Review of in vivo studies of dimethyl sulfoxide cryopreserved platelets

A literature review was conducted to assess the efficacy and safety of dimethyl sulfoxide (DMSO) cryopreserved platelets for potential military use. In vivo DMSO cryopreserved platelet studies published between 1972 and June of 2013 were reviewed. Assessed were the methods of cryopreservation, posttransfusion platelet responses, prevention or control of bleeding, and adverse events. Using the Department of Defense's preferred 6% DMSO cryopreservation method with centrifugation to remove the DMSO plasma before freezing at -65°C and no postthaw wash, mean radiolabeled platelet recoveries in 32 normal subjects were 33% ± 10% (52% ± 12% of the same subject's fresh platelet recoveries), and survivals were 7.5 ± 1.2 days (89% ± 15% of fresh platelet survivals). Using a variety of methods to freeze autologous platelets from 178 normal subjects, mean radiolabeled platelet recoveries were consistently 39% ± 9%, and survivals, 7.4 ± 1.4 days. More than 3000 cryopreserved platelet transfusions were given to 1334 patients. There were 19 hematology/oncology patient studies, and, in 9, mean 1-hour corrected count increments were 11 100 ± 3600 (range, 5700-15 800) after cryopreserved autologous platelet transfusions. In 5 studies, bleeding times improved after transfusion; in 3, there was either no improvement or a variable response. In 4 studies, there was immediate cessation of bleeding after transfusion; in 3 studies, patients being supported only with cryopreserved platelets had no bleeding. In 1 cardiopulmonary bypass study, cryopreserved platelets resulted in significantly less bleeding vs standard platelets. In 3 trauma studies, cryopreserved platelets were hemostatically effective. No significant adverse events were reported in any study. In summary, cryopreserved platelets have platelet recoveries that are about half of fresh platelets, but survivals are only minimally reduced. The platelets appear hemostatically effective and have no significant adverse events.

Extended storage of autologous apheresis platelets in plasma

BACKGROUND AND OBJECTIVES

The purpose of our studies was to determine the effects of extended platelet storage on poststorage platelet viability.

MATERIALS AND METHODS

Normal subjects were recruited to donate platelets using two different apheresis systems: either the COBE Spectra (n = 58) or the Haemonetics MCS+ (n = 84). Platelet recovery and survival data from the two systems were compared with each other and with in vitro measurements of the stored platelets.

RESULTS

There were no significant differences in either platelet recoveries or survivals between the two machines between 1 and 8 days of storage. Combining the data from both machines, platelet recoveries decreased by 2.6% and survivals by 0.3 days/storage day. In vitro assays did not predict either platelet recoveries or survivals during storage for 5-8 days. After 9 days of storage, pHs were unacceptable (≤ 6.1), suggesting that 8 days will be the longest possible storage time.

CONCLUSIONS

These data suggest that, if stored platelet bacterial contamination issues are resolved, significant extension of platelet storage times is possible.

Glucose ameliorates the metabolic profile and mitochondrial function of platelet concentrates during storage in autologous plasma

BACKGROUND

It is essential that the quality of platelet metabolism and function remains high during storage in order to ensure the clinical effectiveness of a platelet transfusion. New storage conditions and additives are constantly evaluated in order to achieve this. Using glucose as a substrate is controversial because of its potential connection with increased lactate production and decreased pH, both parameters triggering the platelet lesion during storage.

MATERIALS AND METHODS

In this study, we analysed the morphological status and metabolic profile of platelets stored for various periods in autologous plasma enriched with increasing glucose concentrations (13.75, 27.5 and 55 mM). After 0, 2, 4, 6 and 8 days, high energy phosphates (ATP, GTP, ADP, AMP), oxypurines (hypoxanthine, xanthine, uric acid), lactate, pH, mitochondrial function, cell lysis and morphology, were evaluated.

RESULTS

The data showed a significant dose-dependent improvement of the different parameters in platelets stored with increasing glucose, compared to what detected in controls. Interestingly, this phenomenon was more marked at the highest level of glucose tested and in the period of time generally used for platelet transfusion (0-6 days).

CONCLUSION

These results indicate that the addition of glucose during platelet storage ameliorates, in a dose-dependent manner, the biochemical parameters related to energy metabolism and mitochondrial function. Since there was no correspondence between glucose addition, lactate increase and pH decrease in our experiments, it is conceivable that platelet derangement during storage is not directly caused by glucose through an increase of anaerobic glycolysis, but rather to a loss of mitochondrial functions caused by reduced substrate availability.

Acquired cytochrome C oxidase impairment in apheresis platelets during storage: a possible mechanism for depletion of metabolic adenosine triphosphate

BACKGROUND

Intracellular adenosine triphosphate (ATP) levels decline significantly during storage of platelet (PLT) products, in part due to PLT degranulation. However, metabolic ATP stores also become depleted during storage through an unclear mechanism. Since both anaerobic glycolysis and oxidative phosphorylation are important for PLT ATP production, it is possible that the reduction in metabolic ATP reflects impaired oxidative phosphorylation. To assess this, we evaluated the kinetic activity and protein expression of cytochrome C oxidase (CcOX) in stored apheresis PLTs.

STUDY DESIGN AND METHODS

Apheresis PLTs were collected and stored with agitation at 22 ± 2°C for 7 days. In vitro measurements of PLT metabolic state, function, and activation were performed on Days 0, 2, 4, and 7 of storage. Total PLT ATP content, steady-state CcOX kinetic activity, and protein immunoblotting for CcOX Subunits I and IV were also performed using isolated PLT mitochondria from simultaneously collected samples.

RESULTS

Intra-PLT ATP and steady-state PLT CcOX activity declined significantly and in a progressive manner throughout storage while steady-state levels of CcOX I and IV protein remained unchanged. Time-dependent decline in CcOX activity correlated with progressive ATP depletion over time.

CONCLUSION

During storage of apheresis PLTs for 7 days, the parallel decline in CcOX function and intra-PLT ATP suggests development of an acquired impairment in PLT oxidative phosphorylation associated with perturbed ATP homeostasis in stored PLTs.

Cell quality of apheresis-derived platelets treated with riboflavin-ultraviolet light after resuspension in platelet additive solution

BACKGROUND

Previously, we evaluated the Mirasol pathogen reduction technology (PRT) system on platelet (PLT) function before resuspension. We now evaluated this system in the presence of PLT additive solution (PAS).

STUDY DESIGN AND METHODS

Double-dose PLTs (n = 15) were generated using a commercially available apheresis system (Trima, Version 5.2, CaridianBCT) allowing for the resuspension in SSP+ (MacoPharma) immediately after collection. Paired units (n = 30) were PRT treated (M) or remained untreated (C) and analyzed for metabolism (pH, pO(2) , glucose, lactate, adenosine triphosphate [ATP]), swirl, hypotonic shock response (HSR), turbidometric aggregation, CD62P expression, annexin A5 and lactate dehydrogenase (LDH) release, mitochondrial enzymatic reduction activity (MTS), transmembrane mitochondrial potential (Δψ), and surface coverage (SC) during shear-induced adhesion throughout 8 days of storage.

RESULTS

As seen previously, PRT treatment of PLT units, containing a mean of 3.9 × 10(11) ± 0.3 × 10(11) PLTs in 397 ± 10 mL with a 32% to 34% plasma carryover, was associated with significantly (p < 0.001) increased cell activation, acidity, and glycolytic flux. PRT treatment appeared to up regulate both oxidative pathway and adhesional properties as evidenced by significantly higher MTS reduction, oxygen consumption, and shear-induced SC on Day 1 (p ≤ 0.016). While no significant differences were found for LDH release and ATP content (except for Day 8), M units were significantly inferior (p ≤ 0.021) for aggregation (TRAP-6); for Δψ and annexin A5 release (by Day 5); and for swirl, HSR, and MTS reduction (by Day 7).

CONCLUSION

PRT treatment in the presence of PAS was comparable to PRT treatment before resuspension preserving ATP content and mitochondrial function.

Storage age of transfused platelets and outcomes after cardiac surgery

BACKGROUND

The relationship between duration of platelet (PLT) storage, currently limited to 5days, and surgical outcomes has not been established. We tested the hypothesis that PLT storage age was associated with adverse outcomes.

STUDY DESIGN AND METHODS

A retrospective cohort of aortocoronary bypass (CABG) surgery patients from January 1996 to January 2005 receiving one or more PLT transfusions was selected for study. The composite primary ("short-term") outcome was 30-day mortality or prolonged hospital stay. Secondary outcomes included complications and survival to annual follow-up. Multivariable logistic regression models and Cox proportional hazards regression analysis evaluated the association between PLT storage age and outcomes, expressed as an odds ratio (OR) or hazard ratio with 95% confidence intervals (CIs), respectively.

RESULTS

PLT transfusion was administered to 3272 of 10,275 CABG patients and 2578 received units of known storage age, which ranged between 2 and 5days (median, 4days; 25th percentile, 3days; 75th percentile, 5 days). The mortality rate for the 1637 patients receiving a single plateletpheresis transfusion was 3.8%, while 21.6% experienced a prolonged hospital stay or death. After adjusting for the number of PLT and red blood cell (RBC) units transfused, RBC storage age, and preoperative mortality risk, there was no association between PLT storage age and short-term outcome (OR, 1.01; 95% CI, 0.90-1.14), survival (hazard ratio [HR], 1.04; 95% CI, 0.96-1.13), or postoperative infections.

CONCLUSIONS

PLT storage age was not associated with adverse short-term outcomes, decreased long-term survival, or infections after cardiac surgery.

Effects of storage duration and volume on the quality of leukoreduced apheresis-derived platelets: implications for pediatric transfusion medicine

BACKGROUND

Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis-derived PLTs (LR-ADP). However, limited data exist regarding the impact of storage on residual small-volume LR-ADP.

STUDY DESIGN AND METHODS

Standard metabolic testing was performed on residual volumes of LR-ADP after aliquot removal and PLT aggregometry using a dual agonist of ADP and collagen was performed on stored, small-volume aliquots (10-80mL) created from an in vitro model of PLT storage.

RESULTS

Seventy-seven LR-ADP underwent metabolic (n=67) or metabolic and aggregation (n=10) studies. All products maintained a pH value of more than 6.89 throughout storage. Lactate and pCO(2) increased proportionally with longer storage time. Regardless of acceptable metabolism during storage, aggregation in 10- to 20-mL aliquots was impaired by Day 4 and aliquots less than 40 mL demonstrated the most dramatic decrease in aggregation from baseline.

CONCLUSIONS

Despite maintenance of acceptable metabolic conditions, residual volumes of LR-ADP develop impaired aggregation in vitro that may adversely affect PLT survival and function in vivo. At volumes below 40mL, LR-ADP revealed reduced aggregation. As a result, it is recommended to monitor and record volumes of LR-ADP used for pediatric transfusion. Moreover, once LR-ADP attain a volume of 50mL or less on Day 4 or Day 5 of storage, consider discarding these products until their in vivo efficacy can be studied.

The platelet storage lesion

The gradual loss of quality in stored platelets as measured collectively with various metabolic, functional, and morphologic in vitro assays is known as the platelet storage lesion. With the advent of pathogen reduction technologies and improved testing that can greatly reduce the risk for bacterial contamination, the platelet storage lesion is emerging as the main challenge to increasing the shelf life of platelet concentrates. This article discusses the contribution of platelet production methods to the storage lesion, long-established and newly developed methods used to determine platelet quality, and the significance for clinical transfusion outcome. Highlighted are the novel technologies applied to platelet storage including platelet additive solutions and pathogen inactivation.

Platelet apoptosis and activation in platelet concentrates stored for up to 12 days in plasma or additive solution

BACKGROUND

Several studies suggest that apoptosis of platelets occurs during storage of platelet concentrates (PC). We sought to determine whether storage of PC in additive solution alters levels of apoptosis during storage beyond the current shelf life (5-7 days).

STUDY DESIGN AND METHODS

Pooled buffy coat PC (n = 7) were prepared in either 100% plasma or 70% Composol and stored at 22 °C for 12 days. A third arm of the study stored PC in 100% plasma at 37 °C, which is thought to induce apoptosis. PC were tested for mitochrondrial membrane potential, annexin V binding, microparticles, caspase-3/7 activity and decoy cell death receptor 2, as well as standard platelet quality tests.

RESULTS

Composol units remained ≥pH 6·88, with 36% lower lactate and higher pH vs plasma by day 12 (P < 0·001). Platelet function was better maintained, and activation and apoptotic markers tended to be lower in Composol units towards the end of storage. However, levels of all apoptosis markers assessed were not significantly different in units stored in Composol. Storage at 37 °C saw stronger correlation of apoptotic markers with standard quality tests compared to 22 °C, but loss of correlation of caspase-3/7 activity with other apoptosis markers.

CONCLUSION

We conclude that storage of platelets in 70% Composol vs 100% plasma does not increase the rate of platelet apoptosis. Our data agree with other studies suggesting that platelet apoptosis is sequential to high levels of activation, but share a significant degree of overlap.

Usefulness of delta value of platelet parameters on ADVIA 120 for the functional reactivity of stored platelets

An agonist-induced expression of CD62P by flow cytometry analysis for evaluating platelet functional reactivity has some disadvantages. We investigated the usefulness of platelet parameters by ADVIA 120 to predict an agonist-induced expression of CD62P in stored platelets. The CD62P expression by flow cytometry and the platelet parameters by ADVIA 120 were studied in samples from 27 platelet pheresis products. Delta (Delta) values were calculated as the degree of change of the platelet parameters studied with or without adenosine 5'-diphosphate sodium (ADP) stimulation. The CD62P expression of the ADP-activated platelets were correlated with the Delta platelet count (r=0.517) in the short-term storage group (within 10 hr from preparation), with the platelet component distribution width (PCDW) without ADP (r=-0.744) and the DeltaPCDW (r=-0.755) in the long-term storage group (after 10 hr from preparation). Therefore, the delta values of platelet parameters on ADVIA 120 analysis in platelets between with and without ADP stimulation could be useful as a simple predictor for the functional reactivity of stored platelets.

The platelet storage lesion

The continuous increase in the demand for platelet transfusion has necessitated the need to establish standards for determining the quality of platelets during storage. Bacterial contamination of platelet products and deleterious changes in structure and function referred to as the platelet storage lesion (PSL), have restricted the platelet shelf life to 5 days. The PSL and platelet health variables have been well studied and documented. The precise correlation between in vitro assays and in vivo platelet recovery and survival is yet to be established. This review presents an overview of the current understanding of PSL and the novel approaches being developed to negate the storage lesion.

Effects of anticoagulant on pH, ionized calcium concentration, and agonist-induced platelet aggregation in canine platelet-rich plasma

OBJECTIVE-To compare effects of 3.8% sodium citrate and anticoagulant citrate dextrose solution National Institutes of Health formula A (ACD-A) on pH, extracellular ionized calcium (iCa) concentration, and platelet aggregation in canine platelet-rich plasma (PRP). SAMPLE POPULATION-Samples from 12 dogs. PROCEDURES-Blood samples were collected into 3.8% sodium citrate (dilution, 1:9) and ACD-A (dilution, 1:5). Platelet function, pH, and iCa concentration were evaluated in PRP. Platelet agonists were ADP, gamma-thrombin, and convulxin; final concentrations of each were 20microm, 100nM, and 20nM, respectively. Washed platelets were used to evaluate effects of varying the pH and iCa concentration. RESULTS-Mean pH and iCa concentration were significantly greater in 3.8% sodium citrate PRP than ACD-A PRP. Platelet aggregation induced by ADP and gamma-thrombin was markedly diminished in ACD-A PRP, compared with results for 3.8% sodium citrate PRP. Anticoagulant had no effect on amplitude of convulxin-induced platelet aggregation. In washed platelet suspensions (pH, 7.4), there were no differences in amplitude of platelet aggregation induced by convulxin or gamma-thrombin at various iCa concentrations. Varying the pH had no effect on amplitude of aggregation induced by convulxin or gamma-thrombin, but the aggregation rate increased with increasing pH for both agonists. CONCLUSIONS AND CLINICAL RELEVANCE-Aggregation of canine platelets induced by ADP and gamma-thrombin was negligible in ACD-A PRP, which suggested an increase in extraplatelet hydrogen ion concentration inhibits signaling triggered by these agonists but not by convulxin. Choice of anticoagulant may influence results of in vitro evaluation of platelet function, which can lead to erroneous conclusions.

Membrane array-based differential profiling of platelets during storage for 52 miRNAs associated with apoptosis

BACKGROUND

Enucleated platelets (PLTs) utilize posttranscriptional gene (mRNA) regulation (PTGR) for their normal morphologic and physiologic functions, which are altered in their ex vivo storage, also collectively referred to as storage lesions. While cellular micro-RNAs (miRNAs) play a significant role in posttranscriptional gene (mRNA) regulation by binding to their target mRNAs, comprehensive analysis of apoptosis-associated miRNAs and global changes in their profiles during PLT storage have not been evaluated to date.

STUDY DESIGN AND METHODS

In this report room temperature-stored PLTs of Days 0, 2, and 9 were analyzed by differential profiling for 52 apoptosis-associated human miRNAs. After total RNA extraction from the samples, a membrane array-based miRNA analysis was carried out. Prediction of target genes was performed by bioinformatics-based approaches.

RESULTS

Our analysis revealed that during storage, Let-7a, -7c, -7e, -7f, -7g, and -7i miRNA profiles of the PLTs were barely detectable, while levels of miR-150, -151, -152, -184, -188, -196a, -197, and -202 remained at high levels in PLTs. The rest of the miRNA levels were in between. However, two miRNAs, Let-7b and miR-16, distinctly demonstrated an increasing trend while miR-7 and miR-145 showed a decreasing profile during PLT storage. For these four miRNAs, we also identified their potential target mRNAs.

CONCLUSIONS

Overall, these results confirm the fact that miRNAs do exist in PLTs, and among 52 apoptosis-specific miRNAs studied, only a few selected miRNAs did perturb during PLT storage. Future experimental evaluation of these miRNA-target mRNA interactions will provide new insights into the molecular mechanisms of PLT storage-associated lesions.

Cell integrity and mitochondrial function after Mirasol-PRT treatment for pathogen reduction of apheresis-derived platelets: Results of a three-arm in vitro study

BACKGROUND

Mirasol pathogen reduction technology (PRT) treatment uses riboflavin (vitamin B(2)) in combination with ultraviolet light (UV) to inactivate pathogens in platelet concentrates (PCs). This treatment has been reported to increase glycolytic flux, which could result from damage to mitochondria and/or increased ATP demand.

DESIGN

Triple-dose PCs were collected by the Trima Accel device. Immediately after splitting, single units were designated to Mirasol-PRT treatment (M), gamma irradiation (X) or remained untreated (C). Platelet (PLT) mitochondrial transmembrane potential (Deltapsi) was evaluated (JC-1 assay) as well as mitochondrial enzymatic activity (MTS assay). LDH release, p selectin expression, glucose/oxygen consumption and lactate production rates were quantified and compared among study groups during 7days of storage.

RESULTS

Immediately after PRT treatment, no significant changes were found in JC-1 signal, MTS activity, and LDH release indicating that PRT treatment did not alter functional/structural cell or mitochondrial integrity as evidenced by LDH release comparable to untreated study groups. In parallel to significantly higher p selectin expression, treated PLTs exhibited significantly accelerated oxygen and glucose consumption rates associated with increased acidity due to higher lactate production rates throughout storage. Despite larger cell populations with depolarized Deltapsi particularly at days 5 and 7, mitochondrial reduction activity of M units as measured by the MTS assay was maintained and appeared to be up-regulated relative to untreated and irradiated controls.

CONCLUSION

Mirasol-PRT treated PLTs increased both glycolytic flux as well as respiratory/enzymatic mitochondrial activity. An increased demand for ATP due to increased alpha granule degranulation may be the driving force for these observations.

Measurement of phosphatidylserine exposure during storage of platelet concentrates using the novel probe lactadherin: a comparison study with annexin V

BACKGROUND

Annexin V binding to platelets (PLTs) is considered the gold standard for monitoring phosphatidylserine (PS) exposure. However, recent comparison of annexin V with the new calcium-independent PS probe lactadherin revealed that annexin V requires a certain threshold of PS exposure (2%-8%) for binding to occur. The aim of this study was to compare annexin V and lactadherin labeling of PLTs in PLT concentrates (PCs).

STUDY DESIGN AND METHODS

Optimal labeling conditions for lactadherin and annexin V were established and then compared in either resting or calcium ionophore (CI)-activated PLTs from normal whole blood. Furthermore, 40 PCs (20 apheresis-derived and 20 pooled buffy coat-derived) were stored under standard blood bank conditions and PLT activation was monitored by measuring PS exposure with annexin V and lactadherin along with CD42b, CD61, and CD62P by flow cytometry on Days 1, 3, 5, and 7.

RESULTS

Lactadherin reported a higher exposure of PS than did annexin V in normal PLTs at submaximal doses of CI. PLTs from both types of concentrate, as expected, demonstrated evidence of increased activation during storage using annexin V, lactadherin, CD42b, or CD62P. However, a significantly higher percentage of PS-positive PLTs was found with lactadherin than annexin V.

CONCLUSION

PS exposure on the surface of stored PLTs has been previously underestimated due to the wide use of annexin V. Lactadherin provides a truer reflection of the degree of PS exposure and offers a new calcium-independent approach to studying PLT activation and/or apoptosis.

[Platelet-leukocyte aggregates as a marker for platelet activation in platelet concentrates]

OBJECTIVES

Several in vitro laboratory tests to assess the quality control of platelet concentrates (PC) are available. Some of them have a good correlation with the platelet recovery index. To assess the quality control of standard PC prepared in our blood bank, we measured the blood gas and the degree of platelet activation.

MATERIALS AND METHODS

SPC were prepared by the PRP method. Fifty-five SPC (45 SPC at day one of storage and 20 SPC at day five of storage) were analysed. Blood gas (pH, PO(2), PCO(2) and bicarbonate concentration) in the SPC were measured by blood gas automate. Platelet activation profile were determined by measuring the percentage of platelet expressing the CD62p (% CD62) and the percentage of platelet-leukocyte aggregate (% PLA).

RESULTS

The pH values of all studied SPC were comprised between 7.0 and 7.6. SPC at day 1 of storage have a significantly higher pH than those at day 5 of storage (7.5+/-0.05 versus 7.3+/-0.14; p<0.001). The % CD62p were higher in SPC at day five compared to the SCP at day one without reaching a statistical significance (28.4+/-15% versus 24.3+/-9.7%, p=0.052). The percentage of PLA were higher in SPC at day one compared to SCP at day five although this difference is not statistically significant (22.2+/-7.5% versus 17.9+/-8.0%; p=0.23).

CONCLUSION

Preparation and storage procedure adopted in our centre did not significantly affect the quality SPC. Our study is the first to assess the PLA in PC. Studies assessing the PLA are warranted to appreciate the clinical impact of this parameter.

Hemostatic and signaling functions of transfused platelets

Metabolic studies have revealed a gradual impairment in platelet integrity during storage, a process termed the platelet storage lesion. Recent evidence shows that stored platelets also lose signaling responses to physiological agonists with impaired integrin activation, secretion, and aggregation of the cells. On the other hand, storage leads to a gain in platelet activation properties, such as release of microparticles and appearance of surface epitopes for their clearance by macrophages. New techniques for measuring flow-induced thrombus formation and platelet-dependent coagulation provide evidence that the hemostatic activity of platelets decreases during storage. Besides pharmacological inhibition, novel storage strategies, like metabolic suppression, should be considered to better preserve platelet functionality while limiting the expression of clearance markers. Understanding the changes that occur in association with the platelet storage lesion and the use of updated storage methods will help to generate platelets for transfusion with optimal hemostatic function and a long circulation time after transfusion.

Past and Future Approaches to Assess the Quality of Platelets for Transfusion

No automated test exists to routinely measure platelet quality. Currently, the short, 5-day shelf life of platelet concentrates is largely dictated by the risk associated with bacterial contamination and not by platelet quality. With the implementation of bacterial testing and pathogen inactivation, platelet quality will become the major determinant for the shelf life of platelet concentrates. However, extended use of platelet concentrates stored beyond 5 days will require quality testing. In addition, high platelet quality would be expected to result in improved clinical efficacy, determined by count increment, improved hemostasis, and lower risk for adverse reactions in recipients. No in vitro quality test has yet demonstrated a good correlation with clinical efficacy or improved hemostasis. This review focuses on those tests of platelet quality that are based on platelet morphology. These include visual inspection of swirling, microscopic morphology score, measurement of light transmission through platelet concentrates, and platelet light scattering techniques. Recently, a new test for platelet quality has been introduced that uses dynamic light scattering. The advantages and remaining challenges for dynamic light scattering before it can become a routine platelet quality test are discussed.

Platelet function under high-shear conditions from platelet concentrates

BACKGROUND

Platelet (PLT) collection and storage affect the functional capacity of PLTs in PLT concentrates (PCs). Therefore, PLTs' functional quality should be studied before transfusion.

STUDY DESIGN AND METHODS

PCs (n = 15) were collected by a standard apheresis procedure (Trima, Gambro BCT) and were stored for 7 days. Samples were taken to assess PLT adhesion and aggregate formation by a cone and plate analyzer (Impact-R, DiaMed) on Days 1, 3, 5, and 7 after harvesting. This device allows testing PLT function under high-shear stress close to physiologic conditions. Concomitantly, P-selectin expression and the residual responsiveness to TRAP-6 were determined by flow cytometry.

RESULTS

PLT adhesion, as measured by surface coverage, decreased during the entire observation period; likewise, the size of aggregates was significantly lower on Days 5 and 7 compared to Day 1 (p < 0.02). P-selectin expression increased from Day 5 to Day 7 (p < 0.04), whereas TRAP-6-inducible expression remained stable until Day 5 of storage and decreased significantly on Day 7 (p = 0.04).

CONCLUSIONS

Our results show that high-shear-induced PLT adhesion and aggregation on the polystyrene surface deteriorate upon storage, suggesting decreased PLT function in vivo. Thus, the Impact-R may be a useful tool to assess the functional capacity of PLTs under various PLT harvesting and storage procedures.

In vitro evaluation of metabolic changes and residual platelet responsiveness in photochemical treated and gamma-irradiated single-donor platelet concentrates during long-term storage

BACKGROUND

Photochemical treatment (PCT) prevents replication of pathogens in platelet concentrates (PCs) by cross-linking nucleic acids and thus affects all cells containing DNA or RNA.

STUDY DESIGN AND METHODS

Fourteen double-dose single-donor PCs were divided into two study arms. The double-dose PCs were split in two identical units, PCT and conventional control PCs. Study Arm A consisted of seven PCT PCs with corresponding untreated controls, whereas Study Arm B consisted of seven PCT PCs with corresponding gamma-irradiated control. Metabolic changes and agonist-induced platelet (PLT) response were evaluated during storage for up to 12 days.

RESULTS

Higher rate of PLT destruction, illustrated by reduced PLT content, increased lactate dehydrogenase levels, and higher CD61+ microparticle formation rate, were observed after PCT. Generally PCT accelerated metabolic changes in PCs and reduced agonist-induced (collagen or thrombin receptor activator peptide [TRAP]) aggregation responses. Flow cytometric analysis of CD62P and CD42b (GPIbalpha) expression showed higher spontaneous PLT activation in PCT PCs from 5 days of storage. Correspondingly, a reduced capacity for up regulation of CD62P expression and down regulation of CD42b was observed in PCT PLTs after stimulation by the agonists ADP or TRAP.

CONCLUSION

Generally reduced in vitro PLT quality was observed after PCT during storage for up to 12 days, with marked reduction from 5 days of storage. Compared to conventional PCs, reduced agonist-induced aggregation and glycoprotein expression were observed after PCT during storage, corresponding to significantly higher level of spontaneous PLT activation in PCT PCs. Clinical studies of efficacy and safety of PCT PCs stored for more than 5 days are recommended.

In vitro function and phagocytosis of galactosylated platelet concentrates after long-term refrigeration

BACKGROUND

Short-term refrigeration of platelets (PLTs) in the absence of plasma results in their rapid clearance after transfusion. Blocking beta-N-acetylglucosamine (beta-GlcNAc) residues of glycoprotein Ibalpha (GPIbalpha) with galactose prevents binding of refrigerated human and mouse PLTs to macrophages and prolongs the circulation times of refrigerated mouse PLTs. PLT-associated galactosyltransferase efficiently galactosylates chilled PLTs in the presence of its substrate UDP-galactose is added to PLT-rich plasma.

STUDY DESIGN AND METHODS

To characterize the hemostatic function of refrigerated and galactosylated human PLTs processed in the blood bank, PLT aggregation was studied in vitro under static and flow conditions and expression of integrin beta3 (CD61), CD62P (P-selectin), GPIbalpha (CD42b), annexin V binding, and integrin alphaIIbeta3 activation with flow cytometry. Affinity of macrophages for galactosylated refrigerated PLTs was evaluated with THP-1 cells, which recognize and phagocytize refrigerated PLTs.

RESULTS

PLTs refrigerated and galactosylated for 14 days 1) maintained their ability to aggregate when exposed to agonists in a standard aggregometry assay, 2) showed less pronounced changes in surface expression of GPIbalpha compared with room temperature (RT)-stored PLTs, 3) increased P-selectin expression, and 4) were poorly phagocytized by differentiated THP-1 cells in vitro. In addition, it is shown that refrigeration of PLTs does not affect their adhesive properties under in vitro flow conditions.

CONCLUSION

It is shown that refrigerated human PLTs retain in vitro function better than RT PLTs during storage and demonstrate that galactosylation prevents recognition of stored refrigerated PLTs by macrophages in vitro.

Platelet ADP response deteriorates in synthetic storage media

BACKGROUND

During storage under blood bank conditions, platelets (PLTs) are known to secrete ADP. PLT stimulation by ADP results in refractoriness to restimulation, making this response one of the most unstable PLT reactions. The goal of this study was to evaluate the ADP-induced responses of PLTs stored in full plasma or in plasma and additive solution (AS).

STUDY DESIGN AND METHODS

Surface expression of P-selectin, ADP-induced aggregation, and reconstituted whole-blood thrombus formation were determined on collagen surfaces in a perfusion model with PLTs that were stored for 4 days either in plasma or in the presence of plasma with PAS-II or Composol.

RESULTS

After 4 days of storage in PAS-II but not in Composol, the percentage of PLTs that had secreted granule contents (P-selectin) was increased, when compared to PLTs stored in full plasma. Maximal aggregation in response to ADP was reduced for PLTs stored in PAS-II or Composol. Resuspension of these PLTs in plasma at 37 degrees C for 1 hour caused partial recovery of the aggregation response. Addition of apyrase to PLTs in AS preserved the responsiveness toward ADP. Titration experiments indicated that this response gradually decreased with decreasing plasma concentration. The functional significance of these findings was demonstrated by perfusion experiments. Thrombus formation on collagen was significantly higher for PLTs stored in full plasma than for PLTs stored in PAS-II or Composol.

CONCLUSIONS

Storage of PLTs in the presence of AS under blood bank conditions induces deterioration of the PLT responsiveness to ADP compared to PLT concentrates in 100 percent plasma. Higher plasma-to-AS ratios result in better preserved responses.

Platelets: testing, dosing and the storage lesion--recent advances

The demand for platelet transfusions continues to grow. Several complementary approaches that may help meet this demand in the future are reviewed. First, platelet bacterial testing is beginning to allow the extension of platelet storage beyond 5 days. Studies are also underway aimed at better preserving viability and function during ex vivo platelet storage: additive solutions and other approaches are being developed to try to negate the "platelet storage lesion." Finally, new approaches to dosing platelets may help extend the limited supply.

Assessment of the correlation of platelet morphology with in vivo recovery and survival

BACKGROUND

There is continuing interest in the development of in vitro tests evaluating the in vivo function, recovery, and survival of platelets stored for transfusion. A recent forum concluded that no completely reliable test exists, although discoid morphology indicates a platelet's good health. We evaluated a novel device, the NAPSAC (Noninvasive Assessment of Platelet Shape and Concentration), designed to determine noninvasively the proportion of discoid platelets in a stored concentrate, as well as platelet concentration.

STUDY DESIGN AND METHODS

Twenty-eight plateletapheresis concentrates stored 24 hours in PL-146 were evaluated. Percent discoid platelet results were correlated with radiolabeled autologous recovery and survival performed using 111Indium oxyquinoline and calculated using linear (L) and multiple-hit (M) models. pH of 8 concentrates was raised at the end of storage with 6N NaOH. Platelet concentration measured by NAPSAC and Coulter Thrombocounter C was compared in 256 plateletapheresis products.

RESULTS

Percent discoid platelets at 24 hours did not correlate significantly with platelet recovery or survival (recovery L = 0.29, M = 0.28; survival L = 0.16, M = 0.03). Raising the pH (mean 6.38 to 6.94) resulted in a significant increase in percent discoid platelets (21% to 41%). Platelet concentration values for both methods studied were linearly correlated with a slope of 1.01 +/- 0.03, r = 0.81.

CONCLUSION

Percent discoid platelets was not predictive of posttransfusion platelet recovery or survival. The results suggest that non-discoid platelets may survive posttransfusion and even revert to discoid shape, since raising the pH approximately doubled the percent of discoid platelets. The NAPSAC was shown to be a reliable instrument for noninvasively determining platelet concentration in PL-146 concentrates.