Alloimmunization of patients by blood units harboring distinct DEL variants.

The alloimmunization potential of many RHD variants is unknown, and it can be explored by lookback and traceback studies. Hema-Quebec (HQ) investigated the RHD status of 3980 D- repeat blood donors. Thirteen were found to be RHD positive: 4 RHD1p, and 1 RHD487delACAG, which show a Dphenotype;and 1 RHD885T and 7 RHD(93-94insT) causing a DEL phenotype when C antigen is present. Look back studies were done to verify the alloimmunization potential of these eight DEL donors. Coincidentally, Canadian Blood Services (CBS)performed a trace back study by investigating the RHD status of donors after aD- recipient developed anti-Dafter 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-Din 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 trace back 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 DtoD+ to protect against the potential alloimmunization risk.