Quality control testing ensures manufacturers continue to provide the highest quality products. For blood product manufacturers, quality control testing ensures patients receive a safe and effective product. For example, for red blood cell concentrates (RCCs), a blood product given to patients who have low iron or hemoglobin levels due to injury or illness, quality control includes sterility testing, and determining the integrity and quality of the red blood cells.
Monitoring extracellular vesicle content in stored red cell concentrates shows promise as a rapid, non-destructive measure of red blood cell quality.
While current quality control tests ensure products meet safety and quality criteria set by regulatory agencies, they have several limitations. The way the RCC is sampled for testing leaves the product unsuitable for transfusion. Because of the “destructive” nature of the sampling, it cannot be done on an RCC before transfusion. Instead, a small percentage of RCC units is retained for quality control testing at the end of their shelf life (42 days after production). If RCC quality could be accurately tested by a non-destructive sampling method, these units could remain available for transfusion.
The tests are also not sensitive enough to assess subtle changes in RCCs, such as those that recent research has shown can be caused by component manufacturing processes, storage, and donor factors, such as age and sex. Although subtle, these changes may influence product quality and patient outcomes. A screening method that combines non-destructive sampling with ease of use, and can accurately determine RCC quality would help advance our understanding about the potential clinical impacts of subtle differences in RCCs.
In this study, the researchers investigated a quality test based on extracellular vesicles (EVs). EVs are very small membrane-bound blebs shed by cells. Measuring EVs in RCCs may provide information on how product manufacturing impacts quality.
What did the researchers do?
The researchers tested whether measuring EV content in RCCs is a quality indicator that is sensitive to differences in RCCs manufacturing methods and the length of RCC storage. In the first part of this study, they compared two different methods to measure EVs:
Dynamic light scattering using a ThromboLUX device;
Tunable-resistive pulse sensing using a qNano device.
Over the 42-day shelf life of RCCs, they investigated differences in the EV content of RCCs from different donors. They also looked at RCCs prepared by the two different manufacturing methods in use at Canadian Blood Services: whole blood filtration and red cell filtration.
In the second part of this study, the researchers investigated whether small volume portions (aliquots) taken from a RCC and stored in small bags have EV content and red blood cell quality variables comparable to the parent unit. To do this, they measured levels of burst red blood cells (hemolysis) and how well the red blood cells can deform (deformability).
What did the researchers find?
Both EV measurement methods showed that the concentration of EVs increased with storage time in RCCs produced by either manufacturing method
There were differences between the size and number of EVs in RCCs produced by the red cell filtration and whole blood filtration methods:
RCCs prepared by whole blood filtration method showed much larger variability in EV content on all storage days compared to the red cell filtration method.
The size distribution of EVs in RCCs was different between the two methods and changed during storage time.
After controlling for time, EV content measured by dynamic light scattering was significantly associated with some traditional measures of RCC quality, including hemolysis and deformability.
Small aliquot bags appear to contain representative samples of the parent unit. The EV content increased with storage time in both the parent and the small aliquot bags. The EV content was consistent in the six aliquot bags on each testing day.
However, a difference in the EV content between the parent unit and the aliquots developed after 21 days of storage. This suggests that the red blood cells in the aliquots may experience additional stress.
How can you use 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.
About the research team
This work was a collaboration between Canadian Blood Services scientist, Jason Acker, and Canadian Blood Services adjunct scientist, Elisabeth Maurer. Dr. Acker is also a professor in the department of laboratory medicine and pathology at the University of Alberta. Dr. Maurer is also a clinical associate professor at the University of British Columbia and the chief technology officer at LightIntegra Technology Inc., a company that she founded in 2008 to develop the ThromboLUX dynamic light scattering device.
This research unit is derived from the following publication(s)
 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; doi:10.1111/trf.14782.
Acknowledgements: This work received funding from a Canadian Blood Services Intramural Grant, funded by the federal government (Health Canada) and the provincial and territorial ministries of health. The views herein do not reflect the views of the federal government of Canada, or provincial or territorial governments. RA is supported by the Saudi Arabian Cultural Bureau in Canada. Infrastructure funding from the Canada Foundation for Innovation and the Michael Smith Foundation for Health Research for the UBC Centre for Blood Research are acknowledged. Canadian Blood Services is grateful to blood donors for making this research possible.
Keywords: Red blood cell, quality control, extracellular vesicles, hemolysis.