The other parts of the blood group alphabet: meeting the diverse requirements of our changing population

Blood donation programs must change in response to population ageing and becoming more ethnically diverse

Lifeblood, a branch of the Australian Red Cross, has supplied clinically critical blood products for more than 90 years and continues to maintain the highest standards of quality and safety. In this issue of the MJA, Lifeblood researchers Hirani, Weinert and Irving report their findings on the prevalence of ABO RhD blood groups in the community, including the increasing proportion of RhD‐positive first‐time blood donors, reflecting the changing ethnic make‐up of the Australian population.1

The ABO blood group system is the most important for transfusion safety. Demand for group O RhD‐negative red blood cells, which can be used in emergency or life‐threatening situations involving mass blood loss, remains high. Demand for red cells in Australia increased during the coronavirus disease 2019 (COVID‐19) pandemic, while blood donations declined. The demand for O RhD‐negative stock accounted for 17.4% of total red cells supplied during 20191 and for 16.4% during the 2021 calendar year (personal communication, Joanne Pink, Red Cross Lifeblood, February 2022). Only 8.7% of first‐time donors in 2019 were group O RhD‐negative.1 This discrepancy between supply and demand places enormous pressures on our blood supply, and could affect care planning, including for the provision of emergency stocks in rural and remote areas.

Australia also has an ageing population.2 Some conditions requiring chronic red cell transfusion support are more frequent among older people, and people with such conditions are living longer. The change in the population age distribution increases the ratio of the number of people needing red cell transfusion support, now or in the future, to the number of younger people eligible to donate blood. Despite much research into antigenically modified red blood cells and cell‐free haemoglobin solutions,3 no readily available, safe, and effective alternatives to allogeneic red cell transfusion are available for many chronic clinical conditions.

People who require chronic red cell transfusion support must be provided with ABO‐compatible blood, placing pressure on ensuring that supply matches the required blood groups, as highlighted by Hirani and colleagues.1 Red cells also express a variety of non‐ABO antigens; 43 distinct human blood group systems are recognised (including the Rh, Kell, Kidd, Duffy, and MNS systems), and more than 300 antigens.4 People receiving chronic transfusion support for conditions such as sickle cell disease, thalassaemia major, and myelodysplastic syndromes, and patients undergoing haematopoietic stem cell transplantation can produce allo‐antibodies against several of these non‐ABO antigens.5,6 These antibodies are often associated with increased risk of transfusion‐induced haemolysis.7 Avoiding reactions caused by non‐ABO red cell allo‐antibodies requires that patients receive ABO‐compatible red cells that also lack the non‐ABO antigens that can elicit their production.

Australia has a multi‐ethnic population, but blood donors are still predominantly European in background (personal communication, Joanne Pink, Red Cross Lifeblood, February 2022). This increases the risk of supply and demand mismatches beyond ABO/RhD group compatibility, of discrepancies between the non‐ABO antigenic profiles (“extended phenotypes”) of the red cells needed for patients of non‐European backgrounds and those of traditional donors of red cells. Australia is now home to people from many parts of Asia and Africa, where some diseases requiring chronic transfusion, such as sickle cell anaemia, are more prevalent,8 and the prevalence of non‐ABO antigens may differ markedly from that in European populations. For example, Duffy antigens are expressed much less frequently in African than in European populations,9 and a person of African origin with sickle cell disease may produce anti‐Duffy antibodies in response to transfusion, possibly leading to haemolysis. After clinical or laboratory recognition of the problem, red cells without the relevant Duffy antigens must be supplied for future transfusions.

The growing and increasingly ethnically diverse Australian population, the rising proportion of older people, the climbing prevalence of chronic conditions that require ongoing red cell transfusion support, and differences between the supply of and demand for specific ABO blood groups and red cell stocks with certain non‐ABO antigen profiles together pose considerable problems for securing our future blood supply. The proportion of blood donors whose red cells are genotyped or who undergo extended phenotyping to support complex transfusion requirements is increasing; 154 new donors with rare blood groups were identified across Australia during 2020–21 (personal communication, Joanne Pink, Red Cross Lifeblood, February 2022).

June 14 is World Blood Donor Day. Let’s celebrate and support Lifeblood achieve the necessary supply and diversity of blood stocks facilitated by their donor recruitment and red cell genotyping and phenotyping programs. As clinicians, we can help expand donation programs, promote educational activities, and encourage excellent patient blood management in transfusion decision‐making: right patient, right treatment, right time.