Reducing the infectivity of blood components--what we have learned

The safety of the nation's blood supply has improved over the last several years as a result of more intensive donor screening and viral testing. Concurrently, there has been more judicious use of blood components. Although the risk is small, transmission of blood borne viruses, bacteria and parasites can occur. Investigators have studied a myriad of processes for pathogen depletion and/or inactivation, including the use of chemicals, extended storage, filtration, heating, irradiation, photochemicals and washing. Pasteurization, methylene blue and solvent-detergent processes have been introduced in parts of Europe for improving the safety of plasma used for transfusion. The FDA is reviewing a license application for the solvent-detergent process. For red cells, use of highly efficient leukodepletion filters is believed to be equivalent to antibody testing for the prevention of CMV disease transmission. Otherwise, no successful treatments have yet been identified for red cells or platelets. Several photochemicals, which may be useful for treating these components, are being studied. However, there appear to be trade-offs between the extent of pathogen inactivation, platelet or red cell damage, and genotoxicity. These as well as other biological parameters and operational issues will need to be further evaluated before implementation can be considered.