More of the Australian population has a positive blood type today compared to the mid-90s, according to new figures.
Key points:
- The first Australia-wide study of its kind in nearly 30 years found the population's blood types are changing
- A larger proportion today has positive blood, and B and AB types increased by 2-4 per cent
- These changes reflect migration and the influx of diverse genes that comes with it
A trio of researchers from Australian Red Cross Lifeblood analysed blood types from more than a million people from across the country, and found rates of a couple of traditionally rarer blood types also jumped up a few percentage points.
The blood type audit results were published in the Medical Journal of Australia.
Rena Hirani, who led the study, says information about the nation's shifting blood types not only gives blood donation organisations a better idea of what they can collect from the community, but it may also affect how emergency blood transfusions are done down the track.
"Now we can start to make some plans for the future [such as] outreach programs to various different communities to diversify the cultural representation of our blood donors," Dr Hirani said.
"If Australia continues … becoming more positive, then I think we could possibly look at how positive blood could become the universal type that we use in some emergencies."
What's behind this blood type shift?
Like eye colour, your blood type is inherited, and it refers to the presence or absence of certain molecules, called antigens, scattered over the surface of your red blood cells.
When we see blood types written as, say, "O positive" or "AB negative", this provides information about two different blood group systems.
For the A, B, O and AB part, that's dictated by what your parents pass on: your mother and your father each gave you an A, B or O version of the gene.
A and B genes are dominant, while O is recessive. So if you get an A from your mother and an O from your father, your blood type is A.
If you get an A and a B, your blood type is AB, and you have both A and B antigens on your red blood cells. Type O blood has no A or B antigens.
The positive or negative bit is shorthand for the presence or absence of an antigen called Rhesus D.
Again, this is inherited from your parents. Each provides either a positive or negative version of the gene that decides whether the Rhesus D antigen is present on your red blood cells.
If your blood type is negative, you have no Rhesus D antigens.
Different populations have different proportions of blood types, and as people move around, so too do their blood type genes.
For Australia, the fraction of people born overseas has increased steadily since the turn of the millennium, and currently sits just shy of 30 per cent.
Most are English immigrants, but numbers of people moving from China, India and South-East Asia have steadily increased over the past decade.
To see if this was indeed the case, she and her Lifeblood colleagues analysed data from pathology labs and blood donation centres from across the country.
All in all, they included blood types of more than 1.3 million people.
Dr Hirani and her crew found the proportion of negative blood dropped across all A, B, AB and O types in the years since the last audit, which used data from 1993-94.
Meanwhile, the percentage of B and AB positive types substantially increased — which was expected, given these blood types are very common in people from India and China.
There were differences between states and territories too.
The highest proportion of positive blood was found in the Northern Territory, followed by Victoria and New South Wales, Dr Hirani said.
"We think that's because First Nations peoples' genetic background is Rhesus D positive, and [the Northern Territory] is where we find a large number of Indigenous communities.
"Overseas immigrants are moving mostly to the bigger cities like Sydney and Melbourne … and we are finding that Rhesus D positivity follows them too."
What does this mean for blood transfusions?
Erica Wood, a transfusion medicine specialist and head of the Transfusion Research Unit at Monash University, says the new stats highlight ongoing challenges in O negative blood supply.
If a person is transfused with an incompatible blood type — say, someone who's O positive gets A positive blood — there's a risk their immune system will spot the unfamiliar antigens on the red cells and kick off an immune response.
But O negative red blood cells have no A, B or Rhesus D antigens, so can be given to anyone, regardless of their blood type.
"[O negative red blood cells] are needed for O negative patients, but are also used in emergency transfusion settings, before the patient's own blood group is known," Professor Wood said.
Now, with the proportion of O negative population in the single digits, and positive types increasing overall, some people could get O positive blood in a bleeding emergency instead.
"Most patients will be Rhesus D positive so this is fine for them," Professor Wood said.
What about the smaller slice of the population with a negative blood type?
If they get a positive blood transfusion, they might make antibodies against the Rhesus D antigen — like how we make antibodies against the COVID-19 spike protein — but not all will, she added.
But women who may one day have kids will get matched blood or O negative wherever possible, Professor Wood said.
That's because if a woman with a negative blood type makes antibodies against the Rhesus D antigen, and later is pregnant with a baby with positive blood, some of her antibodies may slip through the placenta and into the foetus's bloodstream, where they destroy the developing baby's red blood cells.
And what about blood donors?
As Australia's population changes, the country's pool of blood donors should be representative of this -- but it has a way to go, Dr Hirani said.
"We've had such an influx of people from all around the world, but only one in five of our blood donors represents those communities."
A more diverse donor pool is important: not just to contribute to the Australian blood supply, but to also help people with rare blood types both here and overseas.
Because alongside ABO and Rhesus D types, there are dozens of additional blood group systems with hundreds of different antigens, Dr Hirani said.
"Some of those combinations can only be found in certain ethnic backgrounds.
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2022-03-20 18:30:00Z
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