Bath time for blood cells: improving the red blood cell washing process

As the metabolites are the same ones normally produced in the body, they pose no risk to the majority of transfusion recipients. However, for some patients the metabolites can be harmful. For example, newborns are particularly sensitive to potassium, a metabolite that can affect heart function. In addition, certain metabolites and proteins can be harmful to patients who need regular blood transfusions or those who have a history of bad transfusion reactions. Other at-risk recipients are those who lack IgA-type antibodies. These patients could have severe reactions if they receive blood containing IgA. For all these patients, Canadian Blood Services or Canadian hospitals perform an additional processing step on the red blood cells: they are washed!

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During washing, most of the metabolites and proteins that accumulated in the bag during storage are removed resulting in a safer product. Up until late 2013, Canadian Blood Services used an ‘open’ system to wash red blood cells. After washing with the ‘open’ system, the products are at greater risk of becoming contaminated with bacteria and must be used within 24 hours. This can cause issues in getting these special products to patients. In 2011, Canadian Blood Services began investigating a new process to wash the cells within a ‘closed’ system and store them in a solution containing nutrients as this allows the cells to be stored for longer after washing.

• The quality characteristics of red blood cells washed with the new system were equal to, or better than, those washed using the old system, and were best maintained in a nutrient solution called saline-adenineglucose-mannitol (SAGM).
• Washing red blood cells within the first two weeks of storage and storing the washed red blood cells for a maximum of one week after washing was the best way to maintain an acceptable level of quality.
• Quality was best maintained in ‘washed and irradiated’ red blood cells when they were irradiated within a week of washing, and used within two days of irradiation.
• Under these conditions, both washed and ‘washed and irradiated’ red blood cell products met requirements for all uses except for transfusion to IgA-deficient recipients. Levels of IgA remaining after washing were too high to be safe for these recipients.
• Washing the red blood cells twice could reduce IgA levels to less than 0.05 mg/dL making them suitable for transfusion to IgA-deficient recipients.
• Once the new washing system was implemented adverse transfusion reaction rates did not change, occurring in 0.15 per cent of transfusions both before and after implementation of the new system.
• The longer storage time after washing reduced the number of red blood cell units that were discarded due to expiry, from approximately 4 per cent of all washed units before implementation to less than 1 per cent after implementation. Utilization of washed red blood cell units by the hospitals improved.

This research was conducted in the laboratory of Dr. Jason Acker, a senior development scientist with Canadian Blood Services’ centre for innovation and a professor in the department of laboratory medicine and pathology at the University of Alberta in Edmonton. Based at Dr. Acker’s laboratory, Adele Hansen is project lead with Canadian Blood Services’ centre for innovation, and Tracy Turner and Jayme Kurach are research assistants. Dr. Qi-Long Yi is a senior biostatistician with Canadian Blood Services centre for innovation in Ottawa. Dr. Barbara Hannach is a Canadian Blood Services medical officer based in Toronto. Nayana Sondi is an applications specialist and Dr. Christine Cserti-Gazdewich and Dr. Jacob Pendergrast are physicians and transfusion medicine specialists at the University Health Network in Toronto.