The alloimmunization potential of many RHDvariants is unknown, and it can be explored by lookback and traceback studies. Héma-Québec (HQ) investigated the RHDstatus of 3980 D– repeat blood donors. Thirteen were found to be RHDpositive: 4 RHD*ψ,and 1 RHD*487delACAG,which show a D– phenotype; and 1 RHD*885Tand 7 RHD*(93–94insT)causing a DEL phenotype when C antigen is present. Lookback studies were done to verify the alloimmunization potential of these eight DEL donors. Coincidentally, Canadian Blood Services (CBS) performed a traceback study by investigating the RHDstatus of donors after a D– recipient developed anti-D after transfusion of two D– red blood cell (RBC) units. Donor genotyping was done either manually (HQ) or using the Progenika Bloodchip platform (CBS). Donations were traced through computer records. Letters were sent to hospital blood bank physicians to verify the presence of anti-D in recipients and to donors to request repeat samples. A total of 118 RBC units were transfused, 82 to D– recipients. Anti-D was found in three patients transfused with RHD*(93– 94insT)DEL red blood cells. One donor presenting the same DEL variant was involved in the traceback study. Even without strong evidence clearly demonstrating the alloimmunization potential of DEL variants, whenever HQ or CBS identifies a donor harboring a DEL phenotype, his or her D status will be changed from D– to D+ to protect against the potential alloimmunization risk. Immunohematology2013;29:136–140.
