While we at ThromboLUX are mostly focused on improving the outcomes of platelet transfusions, we also strive to improve transfusion medicine as a whole. This is why we were excited to collaborate with Dr. Jason Acker and Ruqayyah Almizraq on a publication which investigated microparticles as a marker of Red Blood Cell quality.1 This blog post briefly summarizes the findings from that publication and provides additional commentary on how it fits in with existing Red Blood Cell Literature.
Screening of red blood cells for extracellular vesicle content as a product quality indicator
Quality control of Red Cell Concentrate (RCC) is currently performed on expired product due to the destructive nature of the current methods. This publication sought to add understanding to the current debate surrounding red cell quality and explore the possibility of using Extra Vesicle (EV) content as a quality measure by comparing it to other in vitro red cell quality measures. From the perspective of ThromboLUX detection, EV content and Microparticle content can be used interchangeably. For the rest of this post, we will mirror the publication and use the term “EV content”.
In the study, red cells were made using either the whole blood filtration (WBF) method which utilizes top-top blood collection sets or the red blood cell (RCF) filtration method which utilizes top-bottom blood collection sets. Two unique methods were used for assessing the EV content of red cell units from day 1 to day 43. The two methods were dynamic light scattering (ThromboLUX, LightIntegra Technology) and tunable resistive pulse sensing (qNano-, IZON Science). The two methods showed good correlation with each other. Both measurement systems showed correlations between EV content and product age as well as hemolysis. Inverse correlations were found between EV content and ATP as well as red cell deformability.
Additional testing on red cells stored in 10 mL aliquot bags showed EV content as measured by ThromboLUX correlated very strongly with hemolysis (R2 = 0.90, p<0.0001). Strong or very strong inverse correlations were found between EV content and ATP (R2 = 0.87, p<0.0001), red cell deformability (R2 = 0.79, p<0.0001), and glucose (R2 = 0.90, p<0.0001).
The conclusion of this publication was that EV content correlates with measures of hemolysis and other in vitro red blood cell quality indicators. This means EV content could be implemented as a routine screening tool for nondestructive QC monitoring of the effects of blood components manufacturing and storage on RCCs.
Placing the publication in context
Much of the debate on red cell quality has focused on the age of red blood cells. There have been numerous observational studies that reported worse outcomes with older red cell units.2 Animal models provide some additional support to the notion that older red cell transfusions are higher risk.3
However, a meta-analysis of 12 randomized control trials totaling 5,229 patients did not find fresh red blood cells superior to older red blood cells.4 More recently, a massive multi-center pragmatic controlled trial known as the INFORM trial analyzed over 20,000 patients who randomly received units that were either the shortest possible storage duration or the longest possible storage duration.5 The INFORM trial found no difference in mortality rates between the two arms. Even when the INFORM data set was reanalyzed to compare patients who exclusively received RCCs stored 7 days or less vs patients who received at least one unit stored over 35 days, no difference could be found.6
It is possible, as we have seen with platelets, that the age of a product is not the driving factor for patient safety and transfusion outcome and that alternative indicators of quality are required to improve patient care. EVs are an indicator of cellular activation or degradation and evidence suggests that like platelet-derived microparticles, red blood cell EVs may also have an impact on the recipient. Monitoring red blood cell EVs could provide information on the impact of donor variabilities, product processing, and length of storage—all of which have been linked to patient outcomes. This paper provides the proof of concept for using routine screening for EV content as a practical alternative to screening red cells by age.
Canadian Blood Services recently wrote a research summary based on this work which wonderfully summarized the importance of this research:
Monitoring EV content in stored RCCs shows promise as a measure of red blood cell quality. EVs are indicative of cellular activation or degradation and change with blood component storage. For blood operators, actively measuring EVs is a valuable quality control test for product and process development programs. This test is sensitive to differences in RCCs due to manufacturing or donor factors that have been linked to patient outcomes. It’s worth noting that the two technologies used in this study use two very different approaches to quantify the EVs in RCCs and give different information on the population of EVs in a sample, so the choice of analytical method used will be important.
The non-destructive sampling of products performed in this study is under investigation by the Centre for Innovation as a potential alternative to retaining RCCs for quality control testing at expiry. This approach could also provide a way to perform pre-transfusion testing. With more research into EVs, their relationship to manufacturing methods, and their link to patient outcomes, measuring EVs in RCC aliquots has the potential to be developed into a non-destructive RCC quality test that could be done in hospitals before a transfusion.
Share your views
We’d like to hear your views on the importance of in vitro quality metrics like hemolysis, ATP, glucose, and red cell deformability to transfusion outcomes. Does a measurement that correlates with all of these have promise as a quality indicator? What other factors are important to consider in terms of red cell quality? Leave a comment below to share your thoughts on this topic.
- Acker JP, Almizraq RJ, Millar D, Maurer-Spurej E. Screening of red blood cells for extracellular vesicle content as a product quality indicator. Transfusion 2018;58:2217-26.
- Wang D, Sun J, Solomon SB, Klein HG, Natanson C. Transfusion of older stored blood and risk of death: a meta-analysis. Transfusion 2012;52:1184-95.
- Klein HG. The red cell storage lesion(s): of dogs and men. Blood Transfus 2017;15:107-11.
- Alexander PE, Barty R, Fei Y, et al. Transfusion of fresher vs older red blood cells in hospitalized patients: a systematic review and meta-analysis. Blood 2016;127:400-10.
- Heddle NM, Cook RJ, Arnold DM, et al. Effect of Short-Term vs. Long-Term Blood Storage on Mortality after Transfusion. N Engl J Med 2016;375:1937-45.
- Cook RJ, Heddle NM, Lee KA, et al. Red blood cell storage and in-hospital mortality: a secondary analysis of the INFORM randomised controlled trial. Lancet Haematol 2017;4:e544-e52.