Anaerobic storage of red blood cells: the need for caution regarding donor red cells with sickle cell trait.

Abstract

Dear Sir, We read with interest the review article entitled “Anaerobic storage of red blood cells” written by Yoshida and Shevkoplyas from the United States, which was published in a recent issue of Blood Transfusion1. The article extolled the virtues and potential advantages of anaerobic red cell storage over conventional storage with respect to mitigation of oxidative red cell damage thus allowing for extended storage with good post-transfusion red cell viability, which could be augmented by the addition of metabolite precursor supplements during storage as demonstrated by many studies1. However, despite an extensive review of the research literature, the authors did not take into consideration the implications of anaerobic storage on the viability of red blood cells from donors with sickle cell trait. Individuals with sickle cell trait have red cells with the HbAS genotype and contain about 40% HbS and 60% HbA2. The abundance of HbA prevents sickling in vivo under normal physiological conditions2. However, studies have shown that sickle cell trait blood stored under conventional conditions (i.e. not anaerobic) has poor filterability during leucodepletion procedures3. Furthermore, it has been demonstrated that the filterability of units of blood from donors with sickle cell trait can be improved by enhanced oxygenation, suggesting that some degree of red cell sickling could occur even during conventional storage and is responsible for the poor filterability indices associated with sickle cell trait3. If conventional storage causes some sickling of sickle cell trait red cells, it is easy to believe that anaerobic storage might trigger massive sickling of such cells as a result of the deliberate deoxygenation during storage. Both deoxygenation and sickling can cause membrane damage of HbS-containing red cells4. Hence, we infer that the deoxygenation associated with anaerobic storage would lead to sickling of sickle cell trait red cells and ultimately result in membrane damage that may adversely affect the cells’ post-transfusion viability. From a clinical perspective, transfusing sickled red cells could be harmful, especially to recipients with sickle cell disease or cardiopulmonary insufficiency. There is, therefore, an urgent need to investigate the impact of anaerobic storage on sickle cell trait red cells. Until this is fully investigated, we believe that the advantages of anaerobic red cell storage may be outweighed by the adverse risk of inducing massive sickling. This is particularly important in African nations that have a high prevalence of sickle cell trait among their donor populations5. Hence, anaerobic red cell storage must be considered with caution and scepticism among ethnic populations with a high prevalence of sickle cell haemoglobinopathy.