Yes, donor-recipient sex is associated with transfusion-related outcomes in critically ill patients

TO THE EDITOR:

Wood and Morton¹ express their opinion that the interpretation of the data in our article is misleading and should not be used to guide patient care. They argue that analyses of much larger databases have not found an association between donor sex and mortality and that the much smaller cohort in our study is therefore not of any further value.

We do not agree and have several reasons to explain why our data should not be ignored. Instead of a general population, this is an analysis of critically ill patients. This subset is known to differ from the ward or out-clinic patients in terms of the outcome of transfusion. More importantly, our analysis is narrowed to those who received unisex transfusions alone, meaning that only patients receiving blood from 1 sex were analyzed. This analysis is less subjected to the effects of transfusions that are unrelated to sex.

We aimed to improve the outcome of transfusion. Suggestions of potential ways to improve clinical care often come from observations, and these are always subjected to bias. Therefore, as we explicitly acknowledge, analysis of observational data should be interpreted with caution, ours included. In our study, there were baseline mortality differences between sexes. This is in line with other observations reporting higher baseline mortality in critically ill male patients. We acknowledge that this difference hampers any comparison between sexes; however, those comparisons may be relevant and should therefore be undertaken. We are transparent about our methodology.

We believe that in clinical care, observations should not be ignored. They can inform trial design, which will hopefully answer the question of whether sex should be taken into consideration while matching donors with critically ill recipients.

Contribution: A.A. and N.P.J. wrote the manuscript.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Abdulrahman Alshalani, Laboratory of Experimental Intensive Care and Anesthesiology, Amsterdam University Medical Centra, AMC Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; e-mail: aalshalani@ksu.edu.sa.