High platelet content can increase storage lesion rates following Intercept pathogen inactivation primarily in platelet concentrates prepared by apheresis

Background: Pathogen inactivation methods for platelet concentrates are increasingly being used in blood banks worldwide. In vitro studies have demonstrated its effects on storage lesion, but little routine quality control data on blood banking outcomes have been reported. Materials and Methods: Swirling of distributed products was monitored before and after implementation of Intercept pathogen inactivation. Metabolic parameters pH, glucose and lactic acid were determined in a random cohort of expired pathogen-inactivated products. Storage lesion indicators in apheresis concentrates with premature low swirling were compared to concentrates with normal swirling. Results: During validation for implementing Intercept pathogen inactivation, pH and glucose levels decreased faster in apheresis platelet concentrates with high platelet content than with low platelet content or than in pathogen-inactivated pooled buffy coat-derived products. In routine products, glucose exhaustion was more often found in apheresis compared to buffy coat-derived platelet concentrates despite 3-7% more plasma carryover in the former. Annual incidence of premature low swirling increased significantly by 50% following implementation of pathogen inactivation implementation for apheresis but not for pooled buffy coat platelet concentrates. In addition, apheresis concentrates with premature low swirling had a significantly higher median platelet count (50 x 10(11)) than unaffected products (35 x 10(11)). Conclusion: The risk of increased storage lesion rates following Intercept pathogen inactivation is higher for apheresis than for buffy coat-derived platelet concentrates, especially when platelet contents are higher than 50 x 10(11)

Factor XI/ADAMTS13 complexes are quantitatively insignificant in human plasma

Reportedly, complexes between factor XI and ADAMTS13 are detected with a commercial ADAMTS13/FXI ELISA kit in plasma and are decreased in thrombotic thrombocytopenic purpura (TTP). Using this kit, control and TTP patient plasma contained varying amounts of signal (25-670% of a reference plasma) but no signal was observed for mixtures of recombinant enzymes, suggesting little interaction. ADAMTS13/FXI complexes were undetectable by immunoprecipitation or gel filtration chromatography in control plasma or mixtures of recombinant proteins. These results suggest that ADAMTS13/FXI complexes are insignificant in plasma and unlikely to affect the function of either protein during normal hemostasis or in TTP

Major Changes of von Willebrand Factor Multimer Distribution in Cirrhotic Patients with Stable Disease or Acute Decompensation

Background There is an unstable balance between pro- and anti-haemostatic processes in patients with cirrhosis. We hypothesized, that in patients with acute decompensation (AD) the major alterations of von Willebrand factor (VWF) could contribute to the pro thrombotic situation as compared to patients with stable (ST) cirrhosis. Patients and Methods We analysed different parameters of VWF, including detailed multimer distribution by densitometry and platelet adhesion, together with a disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) activity and antigen and C-reactive protein (CRP) levels in patients with ST cirrhosis (n = 99), with AD (n = 54) and controls (n = 92). Results VWF antigen, ristocetin co-factor as well as collagen-binding activities were elevated in both cirrhotic groups in a stepwise manner. There was a decrease in high and an increase in low molecular weight multimer ratios in the majority of ST cirrhosis. However, in 24 out of 54 AD patients, ultra-large VWF multimers (ultra-large molecular weight multimers [ULMWM]) were found. ADAMTS13 activity in ST and AD patients without ULMWM was similar to controls (median [interquartile range; IQR]%: 98 [67-132] and 91 [60-110] vs. 106 [88-117], respectively). The presence of ULMWM in AD patients was associated with low ADAMTS13 activity [33 (24-49)%] and high CRP level [23 (7.1-83.6) mg/L]. Adhesion of normal platelets showed a stepwise increase in the presence of cirrhotic plasmas, reaching the highest level in AD patients with ULMWM. Conclusion Characteristic changes of VWF parameters are seen in ST cirrhosis. In AD patients, highly increased VWF and reduced ADAMTS13 activity could be found, along with the presence of ULMWM, which are possible markers and contributors of the disease progression

Blood platelet biochemistry

Defects in platelet function or formation increase the risk for bleeding or thrombosis, which indicates the crucial role for platelets in maintaining haemostasis in normal life. Upon vascular injury, platelets instantly adhere to the exposed extracellular matrix which results in platelet activation and aggregation and the formation a haemostatic plug that stops bleeding. To prevent excessive platelet aggregate formation that eventually would occlude the vessels, this self-amplifying process nevertheless requires a tight control. This review intends to give a comprehensive overview of the currently established main mechanisms in platelet function.status: publishe

Platelets at work in primary hemostasis

When platelet numbers are low or when their function is disabled, the risk of bleeding is high, which on the one hand indicates that in normal life vascular damage is a rather common event and that hence the role of platelets in maintaining a normal hemostasis is a continuously ongoing physiological process. Upon vascular injury, platelets instantly adhere to the exposed extracellular matrix resulting in platelet activation and aggregation to form a hemostatic plug. This self-amplifying mechanism nevertheless requires a tight control to prevent uncontrolled platelet aggregate formation that eventually would occlude the vessel. Therefore endothelial cells produce inhibitory compounds such as prostacyclin and nitric oxide that limit the growth of the platelet thrombus to the damaged area. With this review, we intend to give an integrated survey of the platelet response to vascular injury in normal hemostasis.status: publishe

Residues Arg568 and Phe592 contribute to an antigenic surface for anti-ADAMTS13 antibodies in the spacer domain

Background The majority of patients diagnosed with thrombotic thrombocytopenic purpura have autoantibodies directed towards the spacer domain of ADAMTS13. Design and Methods In this study we explored the epitope specificity and immunoglobulin class and immunoglobulin G subclass distribution of anti-ADAMTS13 antibodies. The epitope specificity of anti-spacer domain antibodies was examined using plasma from 48 patients with acute acquired thrombotic thrombocytopenic purpura by means of immunoprecipitation of ADAMTS13 variants containing single or multiple alanine substitutions. Using similar methods, we also determined the presence of anti-TSP2-8 and CUB1-2 domain antibodies in this cohort of patients. Results Antibody profiling revealed that anti-ADAMTS13 immunoglobulin G1 and immunoglobulin G4 predominate in plasma of patients with acquired thrombotic thrombocytopenic purpura. Analysis of anti-spacer domain antibodies revealed that Arg568 and Phe592, in addition to residues Arg660, Tyr661, and Tyr665, also contribute to an antigenic surface in the spacer domain. The majority of patients (90%) lost reactivity towards the spacer domain following introduction of multiple alanine substitutions at Arg568, Phe592, Arg660, Tyr661 and Tyr665. Anti-TSP2-8 and anti-CUB1-2 domain-directed antibodies were present in, respectively, 17% and 35% of the patients' samples analyzed. Conclusions Immunoglobulin G directed towards a single antigenic surface comprising residues Arg568, Phe592, Arg660, Tyr661 and Tyr665 predominates in the plasma of patients with acquired thrombotic thrombocytopenic purpur

Multinational Analysis of Children Transfused With Pathogen Inactivated Platelets

BACKGROUND: Pathogen inactivated (PI) platelets are a technological advancement in blood safety; however, the pediatric experience is not well characterized. We studied pediatric patients who received transfusions of PI platelets across several centers and countries to determine if transfusion reaction rates differed when compared with conventional platelets. METHODS: This is a retrospective multisite study conducted during 2 time periods. The study period started at the time each site began using PI platelets on a widespread basis, and the control period was a similar timespan before PI introduction. Suspected acute transfusion reactions were compared. RESULTS: The study included 3839 pediatric patients who were 0 to 18 years of age who received \u3e7930 platelet transfusions, in total, across 4 centers in 3 countries between 2013 and 2019. The age distribution of patients in the study and control period was not significantly different (P = .190). There was not a difference in the percentage of patients who had any type of transfusion reaction between the time periods (1.0% and 1.1%, P = .803). There were fewer patients with mild allergic reactions in the study period compared with the control period (0.2% and 0.7% of patients with reactions, respectively, P = .018). CONCLUSIONS: Pediatric patients have the same rate of acutely suspected transfusion reactions when receiving PI or conventional platelet transfusions. Subgroup analysis found fewer mild allergic reactions in the study period, which was contemporaneous to the addition of using platelet additive solution more broadly. Future studies of PI platelets should include children to better assess transfusion efficacy and hemostatic outcomes