The prevalence of clinically significant red blood cell antigens beyond ABO and RhD is changing, reflecting the increasingly multicultural nature of the Australian population.

A study of 490,491 blood donors including 103,798 (21.2%) first-time donors during the calendar year 2019 comprised extended Rh (D, C, E, c and e), Kell (K), Duffy (Fy) and Kidd (Jk) typing as well as S and s antigens in the MNS blood group system.

Australian Red Cross Lifeblood (Lifeblood) has performed routine phenotype testing of Rh and Kell in blood donors since 2006.

Additionally, with increasing demand for phenotyped red cell units particularly for patients with frequent transfusion needs, Lifeblood introduced automated analysers in March 2019 to phenotype selected blood donors for other clinically significant blood group antigens.

The study, published in Pathology [link here], found the prevalence of R1R1 phenotype (D+ C+ E– c– e+) was 20.6% in the total blood donor group and 24.0% in first-time donors.

Yet previous estimates showed the prevalence of R1R1 was 17.3%, the researchers said.

“Overall, the study indicates that the R1R1 phenotype has increased in proportion from previous estimates and that this phenotype is more common in individuals that are group B or AB,” the study said.

“As previously reported group B and AB are more prevalent in people from countries such as China and India, where Australia has experienced relatively high immigration.”

The study also found the prevalence of rr (D– C– E– c+ e+) was slightly higher for the total donor panel compared to previous estimates (19.8% v 16.4%) “as these individuals are preferentially recruited”, but lower in first-time donors (15.2%).

“Therefore, in cases where rr blood is transfused into R1R1 recipients, anti-c antibodies may subsequently form. The formation of this antibody may not be significant in all transfusion settings, but in cases where an R1R1 person requires emergency obstetric transfusion and rr blood is used, the patient could require monitoring for possible development of haemolytic disease of the fetus and newborn (HDFN) during pregnancy.”

In other clinically significant blood group antigens, Fy (a–b–) was most commonly found in donors from Africa (e.g., Zimbabwe, Egypt, Sudan) or Asia (e.g., Iran, Saudi Arabia) and Jk (a–b–) was most commonly found from donors from Asia (Philippines) or donors with a Polynesian background (Tonga, Samoa, New Zealand).

Dr Rena Hirani, a Senior Research Fellow from Australian Red Cross Lifeblood, told the limbic that the new data pairs with ABO and RhD data from 2019 previously published in The MJA [link here].

“So we have very high level ABO information. Now we’re drilling down into the next level of some clinically significant antigen prevalences.”

She said the information will be used for precise forecasting of blood supply needs.

“Now that we’ve put it all together, that’s a national reference resource that we have available for anyone to access. And if we need to target a particular type of phenotype, we at least know what the likelihood of being able to obtain that population is at the moment.”

“It can be used to educate the clinical community about what’s available and what they need to think about when they’re transfusing.”

She said the next step will be to get more information on the types of antibodies that are being formed in patients.

“Western Australia does have an antibody register where patients with antibodies are actually popped into a database so that we can see what types of antibodies are being formed. But Western Australia is a very different population to say New South Wales. We might need to look at doing some more studies in New South Wales to have a more diverse representation of the community.”

The study said the formation of RBC antibodies can have important patient-related consequences. 

“In haematopoietic stem cell transplantation, the presence of RBC alloantibodies may have implications for product infusion or stem cell donor RBC engraftment success,” it said.

“In solid organ transplantation settings, alloantibodies against antigens that are expressed not only on RBCs but also on the transplanted organ, such as those in the Jk family present on renal endothelial cells, may impact transplant outcomes.”