The dynamics of clot formation in fresh-frozen plasma

Increasing the time-to-freezing for clinical apheresis plasma meets quality specifications

BACKGROUND AND OBJECTIVES

In Australia, the vast distances between blood collection centres and processing facilities make it challenging to align supply with demand. Increasing the time to freezing for clinical plasma beyond 6 h would alleviate supply issues. This study aimed to determine the quality of clinical apheresis plasma frozen within 12 h of collection.

MATERIALS AND METHODS

Apheresis plasma (n = 20) collected at donor centres was immediately transported to a blood processing facility, stored at 26°C and sampled aseptically at 6, 8 and 12 h post collection. Frozen samples were thawed, and coagulation factors (F) II, V, VII, VIII and XIII, von Willebrand factor (vWF) and fibrinogen were measured using a coagulation analyser.

RESULTS

FVIII concentrations declined in plasma frozen at 6, 8 and 12 h post collection (1.22 ± 0.27, 1.21 ± 0.25 and 1.16 ± 0.24 IU/mL, respectively) but not significantly (p = 0.3338). Importantly, all components met the FVIII specification (>0.7 IU/mL) for clinical plasma. Fibrinogen concentrations were stable from 6 to 12 h (p = 0.3100), as were vWF concentrations (p = 0.1281). Coagulation factors II, V, VII and XIII were not significantly different (p > 0.05 for all factors).

CONCLUSION

Clinical apheresis plasma can be frozen within 12 h of collection, allowing collections from donor centres further from processing centres and increasing supply.

The effect of pathogen inactivation on cryoprecipitate: a functional and quantitative evaluation

BACKGROUND

As a pooled donor blood product, cryoprecipitate (cryo) carries risks of pathogen transmission. Pathogen inactivation (PI) improves the safety of cryoprecipitate, but its effects on haemostatic properties remain unclear. This study investigated protein expression in samples of pathogen inactivated cryoprecipitate (PI-cryo) using non-targeted quantitative proteomics and in vitro haemostatic capacity of PI-cryo.

MATERIALS AND METHODS

Whole blood (WB)- and apheresis (APH)-derived plasma was subject to PI with INTERCEPT^® Blood System (Cerus Corporation, Concord, CA, USA) and cryo was prepared from treated plasma. Protein levels in PI-cryo and paired controls were quantified using liquid chromatography-tandem mass spectrometry. Functional haemostatic properties of PI-cryo were assessed using a microparticle (MP) prothrombinase assay, thrombin generation assay, and an in vitro coagulopathy model subjected to thromboelastometry.

RESULTS

Over 300 proteins were quantified across paired PI-cryo and controls. PI did not alter the expression of coagulation factors, but levels of platelet-derived proteins and platelet-derived MPs were markedly lower in the WB PI-cryo group. Compared to controls, WB (but not APH) cryo samples demonstrated significantly lower MP prothrombinase activity, prolonged clotting time, and lower clot firmness on thromboelastometry after PI. However, PI did not affect overall thrombin generation variables in either group.

DISCUSSION

Data from this study suggest that PI via INTERCEPT^® Blood System does not significantly impact the coagulation factor content or function of cryo but reduces the higher MP content in WB-derived cryo. PI-cryo products may confer benefits in reducing pathogen transmission without affecting haemostatic function, but further in vivo assessment is warranted.

A 5-serum miRNA panel for the early detection of colorectal cancer

OBJECTIVE

The study aimed to screen microRNAs (miRNAs) that can be used for the early detection of colorectal cancer (CRC) based on differential expression of miRNA in serum.

MATERIALS AND METHODS

A three-stage study was designed with a total of 217 CRCs, 168 colorectal adenomas (CRAs), and 190 healthy controls (HCs). A quantitative reverse transcription polymerase chain reaction was performed in three stages. We screened 528 miRNA expression profiles in the sera of 40 patients (CRC n=20, CRA n=10, and HC n=10) for candidate miRNAs, then 210 serum samples (CRC n=90, CRA n=60, and HC n=60) were used for screening of candidate miRNAs. Three hundred and twenty-five independent individual samples (CRC n=107, CRA n=98, and HC n=120) were used to validate the most differentially-expressed miRNAs in the screening stage, and binary logistic regression was used in the validation stage. A receiver operating characteristic curve was drawn to evaluate the diagnostic accuracy.

RESULTS

A 5-serum miRNA panel (miRNA-1246, miRNA-202-3p, miRNA-21-3p, miRNA-1229-3p, and miRNA-532-3p) effectively distinguished CRCs from HCs with 91.6% sensitivity and 91.7% specificity. The area under the curve (AUC) was 0.960 (95% confidence interval [CI]: 0.937-0.983). In addition, the panel also accurately distinguished CRCs from CRAs with 94.4% sensitivity and 84.7% specificity. The AUC was 0.951 (95% CI: 0.922-0.980).

CONCLUSION

Our 5-serum miRNA panel accurately distinguished CRCs from CRAs and HCs with high sensitivity and specificity. The 5-serum miRNA panel may be a promising prospect for application as a nonintrusive and inexpensive method for the early detection of CRC.

Circulating MicroRNA-21, MicroRNA-23a, and MicroRNA-125b as Biomarkers for Diagnosis and Prognosis of Burkitt Lymphoma in Children

Background

The aim of this study was to investigate the diagnostic and prognostic value of microRNA (miRNA)-21, miRNA-23a, and miRNA-125b in Burkitt lymphoma (BL) in children.

Material/Methods

We recruited 41 children with BL for the case group, 56 children with lymph node inflammation for the positive control group, and 60 healthy children for the negative control group. Real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) was conducted for detection of circulating miRNA-21, miRNA-23a, and miRNA-125b. A receiver operating characteristic (ROC) curve was drawn to compare the diagnostic value of miRNA-21, miRNA-23a, and miRNA-125b. Kaplan-Meier method and log-rank test were used for prognostic analyses.

Results

MiRNA-21 and miRNA-23a had significantly higher expression in cases than in positive and negative controls (all P<0.05). Overexpression of miRNA-21 and miRNA-23a were associated with staging, WBC, upregulated serum lactate dehydrogenase (LDH) level, presence of lymphoma size ≥6 cm, and cluster of differentiation 10 (CD10) expression, while miRNA-125b expression had an association with staging and upregulated serum LDH level (both P<0.05). ROC curves of miRNA-21, miRNA-23a, and miRNA-125b presented an area under curve (AUC) of 0.759, 0.853 and 0.615, respectively. MiRNA-21 and miRNA-23a in combination had an AUC of 0.869. After treatment, both miRNA-21 and miRNA-23a expression were significantly decreased (both P<0.05). Advanced clinical stage, upregulated LDH, and lymphoma size of ≥6 cm were related to low complete remission rate (all P<0.05).

Conclusions

Patients with high expression of miRNA-21 and miRNA-23a had significantly lower complete remission rates and survival rates than those with low expression. Expression of miRNA-21 and miRNA-23a may serve as useful diagnostic and prognostic biomarkers in children with BL.

Comparative biochemical studies of fresh frozen plasma and pooled solvent/detergent-treated plasma (octaplasLG® ) with focus on protein S and its impact in different thrombin generation assay set-ups

BACKGROUND AND OBJECTIVES

The solvent/detergent treatment enables effective and robust inactivation of all lipid-enveloped viruses, but also inactivates partly sensitive plasma proteins such as protein S. The aim of this study was to investigate the thrombin generation capacity of octaplasLG^® , in particular focusing on the function of protein S in thrombin generation assay and the impact of assay settings.

MATERIALS AND METHODS

Sixteen octaplasLG^® batches and 32 units of single donor fresh frozen plasma (FFP) were investigated. For protein S, both functional activity and free antigen levels were measured. Thrombin generation assay was performed using two fluorogenic tests with different triggers. Finally, rotational thromboelastometry was performed.

RESULTS

Mean protein S levels were lower in octaplasLG^® , but a wider range of values was found for FFP. Clotting parameters and thrombin generation capacities overlapped between the two plasma groups as demonstrated using both thrombin generation assays and different triggers. Spiking studies with protein S-depleted plasma, human purified protein S or antibodies against protein S confirmed a correlation between protein S and thrombin generation capacity under specific assay conditions, especially in an assay with low tissue factor concentration.

CONCLUSION

Correlation between protein S and thrombin generation capacity was demonstrated in the TGA. Due to higher variability in protein S content in the FFP group, overlapping haemostatic potentials of the two plasma groups were found.

Microparticles variability in fresh frozen plasma: preparation protocol and storage time effects

BACKGROUND

Extracellular vesicles or microparticles exhibiting procoagulant and thrombogenic activity may contribute to the haemostatic potential of fresh frozen plasma.

MATERIALS AND METHODS

Fresh frozen plasma was prepared from platelet-rich plasma at 20 °C (Group-1 donors) or directly from whole blood at 4 °C (Group-2 donors). Each unit was aseptically divided into three parts, stored frozen for specific periods of time, and analysed by flow cytometry for procoagulant activity immediately after thaw or following post-thaw storage for 24 h at 4 °C. Donors' haematologic, biochemical and life-style profiles as well as circulating microparticles were analysed in parallel.

RESULTS

Circulating microparticles exhibited a considerable interdonor but not intergroup variation. Fresh frozen plasma units were enriched in microparticles compared to plasma in vivo. Duration of storage significantly affected platelet- and red cell-derived microparticles. Fresh frozen plasma prepared directly from whole blood contained more residual platelets and more platelet-derived microparticles compared to fresh frozen plasma prepared from platelet-rich plasma. Consequently, there was a statistically significant difference in total, platelet- and red cell-derived microparticles between the two preparation protocols over storage time in the freezer. Preservation of the thawed units for 24 h at 4 °C did not significantly alter microparticle accumulation. Microparticle accumulation and anti-oxidant capacity of fresh frozen plasma was positively or negatively correlated, respectively, with the level of circulating microparticles in individual donors.

DISCUSSION

The preparation protocol and the duration of storage in the freezer, independently and in combination, influenced the accumulation of microparticles in fresh frozen plasma units. In contrast, storage of thawed units for 24 h at 4 °C had no significant effect on the concentration of microparticles.

An overview of the role of microparticles/microvesicles in blood components: Are they clinically beneficial or harmful?

Blood cells and tissues generate heterogeneous populations of cell-derived vesicles, ranging from approximately 50 nm to 1 µm in diameter. Under normal physiological conditions and as an essential part of an energy-dependent natural process, microparticles (MPs) are continuously shed into the circulation from membranes of all viable cells such as megakaryocytes, platelets, red blood cells, white blood cells and endothelial cells. MP shedding can also be triggered by pathological activation of inflammatory processes and activation of coagulation or complement systems, or even by shear stress in the circulation. Structurally, MPs have a bilayered phospholipid structure exposing coagulant-active phosphatidylserine and expressing various membrane receptors, and they serve as cell-to-cell shuttles for bioactive molecules such as lipids, growth factors, microRNAs, and mitochondria. It was established that ex vivo processing of blood into its components, involving centrifugation, processing by various apheresis procedures, leucoreduction, pathogen reduction, and finally storage in different media and different types of blood bags, can impact MP generation and content. This is mostly due to exposure of the collected blood to anticoagulant/storage media and due to shear stresses or activation, contact with artificial surfaces, or exposure to various leucocyte-removal filters and pathogen-reduction treatments. Such artificially generated MPs, which are added to the original pool of MPs collected from the donor, may exhibit specific functional characteristics, as MPs are not an inert element of blood components. Not surprisingly, MPs' roles and functionality are therefore increasingly seen to be fully relevant to the field of transfusion medicine, and as a parameter of blood safety that must be considered in haemovigilance programmes. Continual advancements in assessment methods of MPs and storage lesions are gradually leading to a better understanding of the impacts of blood collection on MP generation, while clinical research should clarify links of MPs with transfusion reactions and certain clinical disorders. Harmonization and consensus in sampling protocols, sample handling and processing, and assessment methods are needed to achieve consensual interpretations. This review focuses on the role of MPs as an essential laboratory tool and as a most effective player in transfusion science and medicine and in health and disease.

Platelet-derived microparticles trigger THP-1 monocytic cell aggregation and release of pro-coagulant tissue factor-expressing microparticles in vitro

Microparticles (MPs) released by blood or endothelial cells are present in plasma for transfusion. They originate from the collected donor blood or are triggered by the variable steps taking place during collection and production/storage processes of blood components. While MPs may contribute to hemostasis, their presence in transfused plasma may lead to uncontrolled thrombin generation when transfused to susceptible cancer or hypercoagulable patients. Understanding the biochemical and cellular triggers of MP-mediated thrombogenesis is therefore crucial. We isolated platelet MPs (PMPs) present in platelet concentrate supernatant plasma (N-PMPs) or prepared by activation of isolated platelets using 0.1 IU/mL thrombin (T-PMPs). N-PMPs and T-PMPs were characterized by dynamic light scattering and counted by tunable resistive pulse sensing to determine population size and number. T-MPMs, but not N-PMPs, induced immediate, long-lasting, strong aggregation of THP-1 monocytic cells in vitro. In addition, co-cultures of THP-1 cells with both N-PMPs and T-PMPs triggered the generation of pro-coagulant tissue factor (TF)-bearing MPs from THP-1 cells. Therefore, some PMPs may induce THP-1 monocytic cell aggregation in vitro and trigger immune cell-mediated thrombogenicity linked to the release of pro-coagulant tissue factor-bearing MPs. Controlling the impact of the presence of PMPs in transfused blood components in certain patient population or critically ill patients deserves in-depth consideration.

Cellular microparticle and thrombogram phenotypes in the Prospective Observational Multicenter Major Trauma Transfusion (PROMMTT) study: correlation with coagulopathy

BACKGROUND

Trauma-induced coagulopathy following severe injury is associated with increased bleeding and mortality. Injury may result in alteration of cellular phenotypes and release of cell-derived microparticles (MP). Circulating MPs are procoagulant and support thrombin generation (TG) and clotting. We evaluated MP and TG phenotypes in severely injured patients at admission, in relation to coagulopathy and bleeding.

METHODS

As part of the Prospective Observational Multicenter Major Trauma Transfusion (PROMMTT) study, research blood samples were obtained from 180 trauma patients requiring transfusions at 5 participating centers. Twenty five healthy controls and 40 minimally injured patients were analyzed for comparisons. Laboratory criteria for coagulopathy was activated partial thromboplastin time (APTT) ≥ 35 sec. Samples were analyzed by Calibrated Automated Thrombogram to assess TG, and by flow cytometry for MP phenotypes [platelet (PMP), erythrocyte (RMP), leukocyte (LMP), endothelial (EMP), tissue factor (TFMP), and Annexin V positive (AVMP)].

RESULTS

21.7% of patients were coagulopathic with the median (IQR) APTT of 44 sec (37, 53), and an Injury Severity Score of 26 (17, 35). Compared to controls, patients had elevated EMP, RMP, LMP, and TFMP (all p<0.001), and enhanced TG (p<0.0001). However, coagulopathic PROMMTT patients had significantly lower PMP, TFMP, and TG, higher substantial bleeding, and higher mortality compared to non-coagulopathic patients (all p<0.001).

CONCLUSIONS

Cellular activation and enhanced TG are predominant after trauma and independent of injury severity. Coagulopathy was associated with lower thrombin peak and rate compared to non-coagulopathic patients, while lower levels of TF-bearing PMPs were associated with substantial bleeding.

Factor VIII and fibrinogen recovery in plasma after Theraflex methylene blue-treatment: effect of plasma source and treatment time

BACKGROUND

The quality of fresh-frozen plasma is affected by different factors. Factor VIII is sensitive to blood component storage processes and storage as well as pathogen-reduction technologies. The level of fibrinogen in plasma is not affected by the collection processes but it is affected by preparation and pathogen-reduction technologies.

MATERIALS AND METHODS

The quality of plasma from whole blood and apheresis donations harvested at different times and treated with a pathogen-reduction technique, methylene blue/light, was investigated, considering, in particular, fibrinogen and factor VIII levels and recovery.

RESULTS

The mean factor VIII level after methylene blue treatment exceeded 0.5 IU/mL in all series. Factor VIII recovery varied between 78% and 89% in different series. The recovery of factor VIII was dependent on plasma source as opposed to treatment time. The interaction between the two factors was statistically significant. Mean levels of fibrinogen after methylene blue/light treatment exceeded 200 mg/dL in all arms. The level of fibrinogen after treatment correlated strongly with the level before treatment. There was a negative correlation between fibrinogen level before treatment and recovery. Pearson's correlation coefficient between factor VIII recovery and fibrinogen recovery was 0.58.

DISCUSSION

These results show a difference in recovery of factor VIII and fibrinogen correlated with plasma source. The recovery of both factor VIII and fibrinogen was higher in whole blood plasma than in apheresis plasma. Factor VIII and fibrinogen recovery did not appear to be correlated.

Platelet microparticles: detection and assessment of their paradoxical functional roles in disease and regenerative medicine

There is increasing research on and clinical interest in the physiological role played by platelet microparticles (PMPs). PMPs are 0.1-1-μm fragments shed from plasma membranes of platelets that are undergoing activation, stress, or apoptosis. They have a phospholipid-based structure and express functional receptors from platelet membranes. As they are the most abundant microparticles in the blood and they express the procoagulant phosphatidylserine, PMPs likely complement, if not amplify, the functions of platelets in hemostasis, thrombosis, cancer, and inflammation, but also act as promoters of tissue regeneration. Their size and structure make them instrumental in platelet-cell communications as a delivery tool of platelet-borne bioactive molecules including growth factors, other signaling molecules and micro (mi)RNA. PMPs can therefore be a pathophysiological threat or benefit to the cellular environment when interacting with the blood vasculature. There is also increasing evidence that PMP generation is triggered during blood collection, separation into components, and storage, a phenomenon potentially leading to thrombotic and inflammatory side effects in transfused patients. Evaluating PMPs requires strict pre-analytical and analytical procedures to avoid artifactual generation and ensure accurate assessment of the number, size repartitioning, and functional properties. This review describes the physical and functional methods developed for analyzing and quantifying PMPs. It then presents the functional roles of PMPs as markers or triggers of diseases like thrombosis, atherosclerosis, and cancer, and discusses the possible detrimental immunological impact of their generation in blood components. Finally we review the potential function of PMPs in tissue regeneration and the prospects for their use in therapeutic strategies for human health.

Microparticle profile and procoagulant activity of fresh-frozen plasma is affected by whole blood leukoreduction rather than 24-hour room temperature hold

BACKGROUND

Microparticles (MPs) are small phospholipid-containing vesicles that have procoagulant properties. MPs are thought to contribute to the hemostatic potential of plasma. This study investigated the effects of whole blood (WB) hold time and leukoreduction (LR) on the MP profile and hemostatic potential of fresh-frozen plasma (FFP).

STUDY DESIGN AND METHODS

WB units (n=12) from healthy donors were divided into two pairs and each pair was held at 20 to 24°C for 6 or 24 hours. At the designated hold time, 1 unit from the pair was LR while the other unit was not LR. FFP was prepared by standard procedures, aliquoted, and frozen. The MP content was determined by flow cytometry using an absolute count assay and specific labels for red blood cells (CD235a), platelets (CD41), and phosphatidylserine (PS). The hemostatic potential was determined by thrombelastography (TEG) and coagulation factor assays.

RESULTS

Compared to non-LR-FFP, LR-FFP had significantly lower numbers of MPs, particularly CD41+ MPs and PS-positive MPs (p<0.03). LR-FFP, compared to non-LR-FFP, had a slower clot formation time (p=0.002); lower clot strength (p<0.001); and lower Factor (F)VIII, FXII, and fibrinogen levels (p<0.01). With longer WB hold time, the TEG profile was unchanged, although FVIII levels were decreased as expected (p<0.01). On average FFP units met quality requirements.

CONCLUSION

LR of WB resulted in lower hemostatic potential of FFP in conjunction with depletion of MPs and coagulation factors. Longer WB hold time did not significantly affect the hemostatic potential of FFP as measured by TEG. Acceptable hemostatic quality was maintained for all FFP processing conditions studied.

Evaluation of the hemostatic potential including thrombin generation of three different therapeutic pathogen-reduced plasmas

BACKGROUND AND OBJECTIVES

Several pathogen inactivation methods currently applied to therapeutic plasma may result in products with different hemostatic properties. This study aims at evaluating and comparing the hemostatic potential of different therapeutic plasma preparations currently available in France.

MATERIALS AND METHODS

We studied three types of pathogen-reduced plasma for transfusion (MB/light, Amotosalen/UVA, industrial S/D plasma). Quarantine, non-pathogen-reduced plasma, was used as a control. This study compared more specifically the content in FVIII, fibrinogen (clottable and antigen assays) and ADAMTS-13 and evaluated the intrinsic hemostatic properties using a thrombin generation test [Calibrated Automated Thrombogram (CAT)] at high and low concentrations of tissue factor to assess the maximum quantity of thrombin generated or the contribution of FVIII and FIX in the amplification phase of thrombin generation, respectively.

RESULTS

The median FVIII concentration was >70 IU/dl for each preparation. Endogenous thrombin potential values were significantly different among the methods of plasma preparation (P<0·001) but were all in the range of the values measured in donors' plasma. Control by the thrombomodulin-activated protein C system was preserved in all preparations (>50% inhibition of endogenous thrombin potential). Fibrinogen concentrations were all within normal range but fibrinogen levels were lower in the plasmas treated with photochemical methods. ADAMTS-13 levels were preserved.

CONCLUSION

The hemostatic potential appears well preserved in all therapeutic plasmas tested but there are some differences between preparations, the clinical relevance of which remains to be elucidated.

The effect of prion reduction in solvent/detergent-treated plasma on haemostatic variables

BACKGROUND

Octapharma PPGmbH has recently modified its manufacturing process for solvent/detergent-treated plasma to incorporate a prion reduction step, in which a 3 log reduction has been demonstrated. The current study was undertaken to assess the impact of this procedure on haemostatic variables in the new product OctaplasLG in comparison with standard Octaplas.

METHODS

Production batches of standard Octaplas (n=4) and OctaplasLG (n=16) were assessed for levels of coagulation factors, physiological protease inhibitors, markers of activation and procoagulant microparticles. Global haemostasis was assessed by a thrombin generation test (TGT) and rotational thromboelastometry (ROTEM).

RESULTS

Mean levels of factors: II, V, VII, IX, X, XI, XII and XIII, VWF:Ag, antithrombin, protein C and free protein S were all >75 u/dl. ADAMTS-13 activity levels were normal. Factor VIII and VWF:RCo were >55 u/dl. TGT and ROTEM were similar in both preparations, and microparticles were present at negligible levels. Two units of OctaplasLG had slightly elevated levels of Prothrombin Fragments 1+2, but D-Dimer and thrombin-antithrombin complexes were normal in all batches.

CONCLUSION

These studies indicate that the affinity chromatography procedure used in OctaplasLG does not appear to adversely affect the proven haemostatic quality of Octaplas, while offering a selective reduction in the concentration of pathological prion proteins.

Multiple levels of degradation diminish hemostatic potential of thawed plasma

BACKGROUND

Severe bleeding after injury requires transfusion of blood products, including fresh frozen plasma (FFP). Many centers are keeping thawed plasma (TP) ready for massively transfused patients. According to the American Association of Blood Banks Standards, TP is approved for transfusion up to 5 days after thawing, when stored at 1°C to 6°C. However, there are no clinical data analyzing the effects of the approved 5-day storage on plasma. We hypothesize that the hemostatic potential (HP) of freshly thawed (FFP-0) was superior to plasma stored for 5 days (FFP-5).

METHODS

FFP from 30 single donors were thawed at 37°C and kept at 1°C to 6°C for 5 days. HP was evaluated at day 0 and 5 by measuring kinetics of thrombin generation (TG), kinetics of clot formation by thromboelastography, clotting factors and inhibitors, and cell-derived microparticles (MPs) by flow cytometry.

RESULTS

When comparing FFP-5 to FFP-0, FFP-5 exhibited only 40% of the potential of FFP-0 for TG (6.2 nM/min vs. 14.3 nM/min, p<0.0001), a slower clotting response via thromboelastography (reaction time: 4.3 minutes vs. 3.2 minutes, p<0.0001) and a longer delay in reaching maximum thrombus generation (5.7 minutes vs. 4.6 minutes, p<0.01). Diminished HP was accompanied by a significant decline in multiple coagulation proteins, including FV, VII, VIII, von Willebrand factor, and free Protein S, by up to 30%, and a decrease of 50% in MP counts.

CONCLUSION

The HP and clot forming ability of TP significantly declined with storage. Hence, freshly TP may have a greater ability to restore hemostasis and correct coagulopathy compared with FFP-5. The clinical consequences for transfused patients deserve further exploration.

Thrombin Generation Capacity of Methylene Blue-Treated Plasma Prepared by the Theraflex MB Plasma System

BACKGROUND: Methylene blue (MB) / light treatment is a well-known procedure for the inactivation of pathogens in fresh frozen plasma (FFP). Aim of the current study was to investigate the thrombin generation (TG) characteristics and quality of MB plasma prepared by the Theraflex MB Plasma System. METHODS: Single donor plasma units (n = 18) were MB/light-treated, with sampling before and after processing. Preparation included leukocyte depletion, addition of MB pill prior to illumination, and depletion of MB and photoproducts by filtration. Different plasma parameters and TG were measured. TG additionally was determined in solvent/detergent plasma (n = 8). RESULTS: MB/light treatment significantly affected factors V, VIII and XI, which were decreased by 9-18%. While the antigen level was not affected, fibrinogen according to Clauss was decreased by 7%, correlating with a 12% prolongation of TT and RT. The total amount of free thrombin generated, given as 'area under the curve' (AUC), was comparable for untreated (93 +/- 18% of normal plasma) and MB/light-treated plasma (95 +/- 20%). Also peak thrombin concentration was not significantly affected by treatment (94 +/- 11% (untreated) vs. 96 +/- 12% (treated)). The 'time to peak' value (TTP) was 105% of normal plasma for untreated FFP and 89% for MB-treated plasma. CONCLUSION: For plasma treated with the Theraflex MB Plasma System no profound influence of MB/ light treatment on the characteristics of thrombin generation was detected. In concordance with data from the literature, coagulation factors V, VIII and XI were decreased due to MB/ light treatment. Decrease was less than 20%.

Microparticle sizing by dynamic light scattering in fresh-frozen plasma

BACKGROUND

We have previously shown that fresh-frozen plasma (FFP) contains red blood cell-derived procoagulant microparticles (MPs) that are removable by 0.2 microm filtration. Given the limitations of current methods for accurately sizing MPs, we have applied the novel approach of dynamic light scattering (DLS) to characterize the size distributions of these MPs within FFP.

METHODS

Fresh-frozen plasma was prepared from blood Group A and O donations (n = 10 of each) after an overnight hold of whole blood at 4 degrees C. On the day of analysis, plasma was thawed to 37 degrees C and daughter aliquots were studied pre- and post-filtration (0.2 microm filtration device, Ceveron MFU-500, Technoclone). MP size and dispersity was assessed using a Zetasizer Nano S (Malvern Instruments Ltd), which employs a 173 degrees backscatter detector and an N5 Submicron Particle Size Analyser (Beckman Coulter) using multi-angle measurements (30.1 degrees , 62.6 degrees and 90 degrees ). The analysers presented MP size distribution graphically as intensity plots, mean size, standard deviation and polydispersity index.

RESULTS

Of the instruments used, only the N5 utilizing a 30.1 degrees angle of measurement could detect MPs of the expected size distribution and demonstrate their removal by filtration. MPs (range of mean particle diameters: pre, 101-464 nm; post, 21-182 nm filtration) were significantly smaller post-filtration (P < 0.0001), but polydispersity index (median: pre, 0.746, post, 0.769) exhibited no significant change. There was no significant difference between the size of MPs from blood Group O (pre, 247 nm) and Group A (pre, 289 nm) samples (P = 0.44).

CONCLUSION

Our data demonstrates that DLS offers a novel approach to assessing MP size and distribution, a technique that could be easily adopted as a means of assessing MPs within either FFP or other blood products.