Data mining 2: Digging for deeper understanding of donors and transfusion outcome
What is this research about?
Red blood cell transfusions are the most common procedure in contemporary medicine, and are used to treat a wide variety of conditions from anaemia to massive blood loss after trauma. There are many guidelines on when to give a red blood cell transfusion, but less is known about whether differences in red blood cell donors affect the outcomes of transfusion recipients. Although the donation and red blood cell preparation processes are standardized, there are inherent differences in every red blood cell unit because they come from unique, individual donors
This is the first study to suggest a link between the age and sex of the blood donor and red blood cell transfusion outcomes.
What did the researchers do?
This study linked large databases of patient data with red blood cell donor records to see if donor characteristics (age and sex) had an impact on recipient outcome. This type of analysis is called retrospective because it looks back at events that have already taken place. The researchers collected data relating to blood transfusions in four hospitals in the Ottawa area from Oct. 2006 to Dec. 2013.
Data on each blood donors’ sex and age, collected at the time of donation, were obtained from Canadian Blood Services and were not linked to any other information about the blood donor. Information on red blood cell unit characteristics including the production method and how long the cells were stored was also gathered. Data on the patients who received transfusions, including survival for shorter and longer periods of time, was obtained from hospital databases and the Institute for Clinical Evaluative Sciences of Ontario, respectively.
The study linked red blood cell donor characteristics with recipient outcomes. The primary study looked at the survival outcomes of recipients measured from the date of their first red blood cell transfusion. Death from any cause was included. The complex analysis accounted for recipients who may have received multiple red blood cell transfusions from multiple donors with unique, individual blood characteristics, and that these transfusions occurred at different times. Recipients may also have received other blood products such as platelets or plasma.
All of the recipients were in need of transfusion, but had different illnesses and some were sicker than others. The results were adjusted to take into account each recipient’s age, sex and comorbidities (other illnesses). The analysis compared the survival rate of recipients who received red blood cells with a particular donor characteristic (e.g. red blood cells from a male donor) to those without (e.g. red blood cells from a female donor).
What did the researchers find?
The researchers analyzed data relating to 80,755 donors and their 30,503 recipients. The average age of the recipients was 66.2 years. A total of 187,960 transfusions were administered. Recipients were followed for an average of 2.3 years and the maximum follow-up time was 7.2 years.
Red blood cell transfusion from young donors and from female donors, particularly cumulative transfusions from these donors, showed an association with poorer survival rates in recipients.
How can you use this research?
This type of study is “hypothesis-generating”; in some ways it provides questions rather than answers. The findings of this study show there is still much to understand about the relationship between blood donors, blood products and transfusion outcomes. This is an emerging area of research and this study is the first to link donor characteristics with recipient outcomes. All of the patients in this study needed and received transfusions. This study does not address the question of whether transfusion with blood associated with poorer outcomes is worse than not receiving a transfusion. More research is required before definitive conclusions can be drawn.
The findings relating to donor age are different to preliminary data from animal studies that suggest benefit rather than harm from blood from young donors. However, the findings of this study do reassure current practice regarding older donors: there is no upper age limit on donation in Canada. In recent years, the use of female plasma for transfusion has been discontinued because of an increased risk of transfusion-associated acute lung injury, a potentially life-threatening adverse transfusion event. However, there is little plasma in red blood cell units for transfusion, so the effect seen in this study is unlikely to be caused by a similar mechanism. Further studies are needed to understand the biological basis for the associations found in this study.
The next step is for the results of this study to be confirmed independently, preferably in randomized, controlled clinical trials. Despite the large number of donors and recipients studied, a limitation is that the study took place in a single geographical region in one country. It would be valuable to repeat this type of analysis elsewhere to see if the findings can be generalized. If the results of this study are independently confirmed with rigorous evaluations, this opens up a whole new era of research in blood transfusion. Ultimately, independent confirmation and a better understanding of mechanisms of the effects seen in this study will help inform next steps.
About the research team
The team was led by Dr. Dean Fergusson, senior scientist and director of the clinical epidemiology program at the Ottawa Hospital and Dr. Michaël Chassé, a clinical research fellow also at the Ottawa Hospital and an assistant professor in the department of anaesthesiology and critical care at Université Laval. The work was conducted in collaboration with Dr. Jason Acker, a senior development scientist at the Canadian Blood Services’ Centre for Innovation and a professor at the department of laboratory medicine and pathology at the University of Alberta, Edmonton. Other researchers included colleagues from the clinical epidemiology program and other departments at the Ottawa Hospital, including Dr. Alan Tinmouth, a clinical scientist and the head of general hematology and transfusion medicine at the Ottawa Hospital, an assistant professor in the departments of medicine, and laboratory medicine and pathology at the University of Ottawa, and a medical consultant to Canadian Blood Services, and Dr. Nadine Shehata, a Canadian Blood Services medical officer and scientist based at Mount Sinai Hospital, Toronto.
This research unit is derived from the following publication(s)
Acknowledgements: This research was funded by Canadian Blood Services, the federal government (Health Canada), the provincial and territorial ministries of health and the Canadian Institutes of Health Research. The views herein do not reflect the views of the federal, provincial or territorial governments in Canada. This work was made possible through extensive collaboration between Canadian Blood Services, the Ontario Institute for Clinical Evaluative Sciences and The Ottawa Hospital Data Warehouse.
Canadian Blood Services is grateful to the blood donors and patients who made this research possible.
Keywords: red blood cell, transfusion, outcomes, donor, sex, age