Effect of donor sex on recipient mortality in transfusion
Transfusion is the most widely used medical therapy in modern medicine. It’s estimated that over 110 million units of red cells are transfused each year.
With the sheer number of transfusions, it’s inevitable that some recipients experience adverse reactions or poorer than expected outcomes. Although we can reduce the likelihood of many reactions, there are some outcomes due to recipient and/or donor factors which we can’t necessarily predict.
Each blood donation represents a unique snapshot of the donor’s blood and reflects a combination of genetic and non-genetic donor attributes such as demographic factors (e.g. sex, age, ethnicity, lifestyle), genetic red cell abnormalities (e.g. haemoglobinopathies, enzyme deficiencies), medications and donation interval. Once collected, the blood processing methods and storage conditions will also shape the final product and may also be affected by these donor factors.
The recipient’s response to transfusion is inevitably shaped by similar genetic and non-genetic characteristics although it’s not always clear to what extent. For example, there have been observational studies which suggest the donor’s sex plays a part in the recipient’s survival post-transfusion, for example reports of red cells from female donors, whether previously pregnant or not, resulting in a higher risk of mortality.
A recent article in the New England Journal of Medicine1 reported no significant difference in recipient survival between those receiving red cells exclusively from either male or female donors. In this large Canadian study, data from 8,719 transfusion recipients at 3 Canadian academic medical centres (both inpatients and outpatients) was analysed, with the primary outcome being the patient’s survival as compared to survival in the male donor group.
During the trial, patients were randomised to receive blood from either male donors or female donors, with 5,190 patients (60%) assigned to the male donor group, and 3,529 (40%) to the female donor group. The recipient characteristics (including age, sex, treatment setting, patient type, haematology parameters etc) of both groups were similar.
Following transfusion, the maximum follow-up period was just over 2 years (29 months) with an average of 11.2 months. Over the timespan of the trial 1,141 patients who received female donor blood and 1,712 patients receiving male donor blood died. It was concluded there was no statistically significant difference in overall survival between the two trial groups.
The study’s findings were generally consistent across the analyses of secondary outcomes. However, one interesting finding was that recipients of female donor red cells experienced a 2-times higher incidence of MRSA infection.
The major benefit of this study was the ability to access and analyse large volumes of patient data using electronic medical records, saving incredible amounts of time (and money) spent otherwise manually trawling through patient charts and other records.
However as with all trials, some limitations were noted. Being a Canadian study, the findings may not apply to other countries where donor selection, blood component manufacturing processes or blood banking practices are different. The authors also note that the study only relates to red cell transfusion and so the potential influence of other types of blood component is not determined.
This study of course won’t be the final word of the effect of donor sex on recipient mortality and so we can only await results from further studies.
1. Chassé M, Fergusson DA, Tinmouth A, et al. Effect of donor sex on recipient mortality in transfusion. N Engl J Med. 2023; 388:1386-1395. DOI: 10.1056/NEJMoa2211523.