Packed red cells and blood products from persons with no known risks for exposure to transfusion-transmissible microorganisms (TTM; e.g., malaria, HIV), which have been fully tested and are negative for TTM by a direct assay of viral products (e.g., HBV surface antigen), by an indirect assay of exposure to viruses (e.g., antibodies to HCV and HIV-1) and by ‘surrogate’ assays (e.g., measurement of transaminases, which are nonspecific indicators of hepatic inflammation)