Bub, Carolina Bonet

Abstract Background Rho(D) immune globulin (RhIg) is used to reduce RhD alloimmunization in pregnancy. This study describes potential causes for RhD alloimmunization after the development and implementation of RhIg. Study Design and Methods This retrospective descriptive study investigated RhD‐negative patients born in 1965–2005 with anti‐D newly identified during 2018–2022. Transfusion, pregnancy, intravenous drug abuse, and transplantation were considered potential alloimmunization sources. Results There were 1200 study patients (852 females; 348 males) at 30 institutions in 5 countries (USA, Canada, UK, New Zealand, Brazil). Most patients had a single potential source of alloimmunization identified (857/1200, 71%), most commonly pregnancy among females (537/852, 63%) and transfusion among males (180/348, 52%). When multiple potential sources were included, males were more likely than females to have a history of transfusion (235/348 [68%] vs. 149/852 [17%], p < .0001) and confirmed or suspected intravenous drug abuse (100/348 [29%] vs. 138/852 [16%], p < .0001). Among females with a history of pregnancy, 119/718 (17%) had healthcare access issues, 120/718 (17%) had pregnancy in a country where they may not have received RhIg, and 21/718 (3%) refused RhIg. Among patients with a history of transfusion, males were more likely than females to have received RhD‐positive red blood cells or whole blood (143/235 [61%] vs. 30/149 [20%], p < .0001) and/or platelets (84/235 [36%] vs. 19/149 [13%], p < .0001). Discussion Pregnancy was the most frequently identified potential source of RhD alloimmunization among females. Transfusion was most frequent in males. Intravenous drug abuse as a common potential source among patients with RhD alloimmunization merits further study.

BACKGROUNDABO‐incompatible platelet transfusions are common, and transfusions with ABO‐incompatible plasma are increasing with the use of group A plasma and group O whole blood (WB) in emergencies. Many centers screen blood products for anti‐A and/or anti‐B titers to help prevent hemolysis from ABO‐incompatible transfusions, yet titer methods and definition of high titers are not standardized.STUDY DESIGN AND METHODSThis international multicenter study collected data on anti‐A and anti‐B titer practices for plasma, apheresis platelet (AP), and WB units from January 2015 through December 2017 to determine the prevalence of high‐titer units using local definitions.RESULTSA total of 87,701 plasma, AP and WB units were screened for high‐titer anti‐A and/or anti‐B. High‐titer detection rates for group A plasma ranged 0%–13.6%; group A AP 2.7%–9.3%; group O AP 2.3%–65.7%; and group O WB 6.4%–20.7%. At the one center that collected group B AP, the high‐titer rate was 10.9%. High‐titer rates varied from month to month, as well as between years for a given month. There was no clear pattern of when high‐titer units were donated.CONCLUSIONThe prevalence of high‐titer plasma, AP, and WB units varies by titer method and local definition of high titer. Even at the lowest titer threshold of 50, a significant proportion of units had a high‐titer antibody, although the clinical relevance of this finding needs further investigation.