The development and evanescence of red blood cell antibodies after transfusion: A multi‐institutional prospective study in Japan

Abstract Background Despite several reports on red blood cell (RBC) alloimmunization, the actual prevalence and factors contributing to RBC alloimmunization in transfused patients remain poorly investigated. We examined the association between clinical factors and the development and evanescence of RBC antibodies after transfusion. Study Design and Methods Each participating institution performed antibody screens before and after RBC transfusion. A survey including patient characteristics, results of antibody screen and identification, antibody screen methods, total amount of RBC transfused, and adverse reactions, was conducted. Results Between October 2018 and March 2023, 1194 patients were registered at five institutions. Overall, 958 patients underwent at least one follow‐up RBC antibody screen after transfusion, revealing new antibody development in 44 (4.6%). Anti‐E was identified in 25 patients, anti‐Jk a in 5, and anti‐c in 4. The number of RBC units transfused was significantly associated with antibody development after transfusion ( p < .001). Among 55 patients in whom antibodies were identified after transfusion, including historical antibodies, antibodies evanesced in 18 (33%); anti‐E in 7, anti‐Jk a in 4, and anti‐Le a in 2. Evanescent antibodies were identified more frequently by saline and/or enzyme methods than persistent antibodies ( p = .012). Discussion The number of RBC units transfused can impact antibody development, and antibodies identified only by saline and/or enzyme methods, deemed clinically insignificant, are likely to have a high evanescence rate. Antibody screen should be carefully performed, especially in those receiving a large number of RBC units. Confirming previous antibody screen results should be performed to prevent omitting evanesced antibodies regardless of clinical relevance.