Affiliation: | 1. Transmissible Diseases Department, American Red Cross Holland Laboratory, , Rockville, Maryland;2. Mid‐American Blood Service Division, American Red Cross North‐Central Region, , St Paul, Minnesota;3. Northeast Division, American Red Cross Blood Services, , Farmington, Connecticut;4. Biostatistical Design & Analysis Center, Division of Biostatistics, University of Minnesota, , Minneapolis, Minnesota |