Why do people still make anti-D over 50 years after the introduction of Rho(D) immune globulin? 

Recently published is a large retrospective descriptive study by the Biomedical Excellence for Safer Transfusion (BEST) Collaborative which describes the epidemiology of RhD alloimmunisation in high and high-middle income countries following the development and implementation of RhIg as the standard of care. 

RhD negative adult patients born between 1965–2005 with anti-D alloantibodies identified for the first time during the study period of 2018–2022 were included in the analysis. Data was extracted from laboratory and electronic medical records (EMR) across 30 institutions in 5 countries (United States, Canada, United Kingdom, New Zealand, Brazil). 

There were a total of 1,200 patients (852 females*; 348 males*) with the majority from the United States (921/1200, 77%). The most common single potential source of alloimmunisation in females was pregnancy (537/852, 63%) and a history of transfusion amongst males (180/348, 52%).  

*Patient sex assigned at birth. 

Upon independent analysis of each potential source (including patients with a single potential source or multiple potential sources), males were more likely than females to have a history of transfusion (235/348 [68%] vs. 149/852 [17%], p < .0001) as well as confirmed or suspected intravenous drug abuse (100/348 [29%] vs. 138/852 [16%], p < .0001).  

In females with a history of pregnancy as a source of RhD alloimmunisation, 119/718 (17%) had healthcare access issues, 120/718 (17%) had pregnancy in another country where they may not have received RhIg, and 21/718 (3%) refused RhIg.  

Moreover, one third of patients (393/1200) had other alloantibodies identified in addition to anti-D, most frequently, anti-C (310/393, 79%) and anti-E (115/393, 29%). 

Overall, this large study revealed that the most frequent potential source of RhD alloimmunisation in high and high-middle income countries was a history of pregnancy in females (despite widespread availability of RhIg) and a history of transfusion in males. This study forms an important baseline for monitoring the impact of evolving practices and improvement strategies.  

Reference: 

• DelBaugh RM, Murphy MF, Staves J, Fachini RM, Wendel S, Hands K, et al. Why do people still make anti-D over 50 years after the introduction of Rho(D) immune globulin? A Biomedical Excellence for Safer Transfusion (BEST) Collaborative study. Transfusion. 2025. https://doi.org/10.1111/trf.18202