Pilot Study of Sex-matched vs. Sex-mismatched Red Blood Cell Transfusion

  • End date
    Sep 11, 2022
  • participants needed
  • sponsor
    McMaster University
Updated on 11 March 2022
red blood cell transfusion


Blood transfusion is common for patients in hospital, especially for those in intensive care. Patients receive blood that is matched to them based on their blood group (A, B, AB, O), but not based on sex. This means male or female patients may receive male or female blood. There is some evidence to suggest that giving male patients female blood and female patients male blood (sex-mismatched blood) may be harmful. The investigators think giving males only male blood and females only female blood (sex-matched blood) will be better for the patients and improve their survival. To test this, the study team will randomly give 50% of intensive care patients who require blood only sex-mismatched blood and 50% of intensive care patients only sex-matched blood for their entire hospital stay. Then, health data of patients will be collected to see if either group does better after transfusion. Before this is done as a large study with thousands of patients, it will be attempted as a smaller pilot study with a few hundred patients to be sure the processes suggested make sense and are possible for hospitals and for the blood supplier to follow.


Blood transfusion is one of the most common procedures performed during hospitalization. Approximately 85 million red blood cell (RBC) units are transfused globally each year. RBC units are matched for blood groups but matching for other donor characteristics such as sex, is not considered. By the current standard of care, female or male patients can receive RBCs from male or female donors. However, accumulating data suggests that sex-mismatched transfusions may be harmful.

Sex-mismatched transfusions and transplantations have been associated with poor outcomes. Plasma from female donors is associated with an increased risk of transfusion related acute lung injury (TRALI); sex-mismatched heart transplantation is associated with increased transplant-associated mortality; and stem cell transplants from female donors are associated with worse outcomes.

Anemia is common during critical illness and 20-40% of critically ill patients require a mean of two to five RBC units during admission to the intensive care unit (ICU). Once a patient receives more than six RBC units, virtually all patients (>97%) will have received at least one sex-mismatched RBC. The population of transfused ICU adult patients is already at high risk of death, with a demonstrated 90-day all-cause mortality of 35-37% based on the ABLE study, and in-hospital mortality of 24-34% (institutional data). Thus, new supportive care strategies are needed to improve outcomes of this highly vulnerable patient group.

Transfusion data linked to donor sex spanning a 6-year period was previously analyzed. Using a careful analysis that controlled for covariates and stratified on time-dependent and fixed variables, 25,219 transfusion recipients were retrospectively analyzed and a significant association between male to female RBC transfusions and death [hazard ratio (HR) 1.31, 95% confidence interval (CI) 1.02-1.69] was found. A trend towards higher mortality was also noted with female to male RBCs (HR 1.13: 95% CI 0.92-1.39), and with sex-mismatched vs. sex-matched RBCs overall (HR 1.23: 95% CI 1.04-1.45). These findings suggest that matching RBC transfusions for sex can reduce mortality in ICU patients.

The investigators hypothesize that donor-recipient sex-matched RBC transfusions are associated with improved survival in hospital compared to sex-mismatched RBC transfusions. Sex-matched RBC transfusions may represent an important, readily implementable advance in supportive care of critically ill patients.

Condition Blood Transfusion
Treatment Red blood cells
Clinical Study IdentifierNCT04814264
SponsorMcMaster University
Last Modified on11 March 2022


Yes No Not Sure

Inclusion Criteria

Adults (age ≥18)
Admitted to the intensive care unit
Requiring a red blood cell transfusion

Exclusion Criteria

Requiring a specific red blood cell unit (e.g., rare blood, washed, complex red blood cell antibodies, etc.)
Massively bleeding (i.e. ≥4 units of blood ordered, or Massive Hemorrhage Protocol initiated)
Biological sex unknown
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