Evanescence and persistence of red blood cell antibodies over time: a single-center experience

Alloantibodies may develop after exposure to foreign red blood cell (RBC) antigens. Evanescence occurs when an antibody falls below the sensitivity threshold of methods used in pretransfusion testing. An alloantibody that has evanesced may go undetected, resulting in possible delayed hemolytic transfusion reactions, which lead to increased morbidity and mortality. A survey was conducted to analyze evanescence of alloantibodies over time. A total of 544 patients with 656 alloantibodies were evaluated. Median follow-up was 294 days (range 3-3852 days). Analysis showed that patient age at detection of alloantibody (p = 0.037), sex (p < 0.001), results of initial RBC antibody screen (p < 0.001), RBC transfusion (p < 0.001), length of follow-up period (p < 0.001), and alloantibody specificity (p = 0.004) significantly influenced the time of evanescence. Evanescence rate was the highest for anti-Jk^a, anti-C, and anti-M and the lowest for anti-Fy^a and anti-D specificities. Evanescence of alloantibodies represents a significant problem in routine pretransfusion testing. Beyond improving testing by implementing more sensitive methods, there is a place for preventive usage of extended antigen-matched RBC units or the application of post-transfusion protocols. Sharing of antibody information across centers can also improve transfusion safety in these centers.