Who has ever heard of the groups “Bombay” or “Vel Negative”? These are not musical formations, but rare blood whose donors are essential to meet the diverse needs that go beyond groups A, B or O.
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Although the blood appears to be identical, blood types have many differences depending on the person and genetic background.
In addition to blood groups A, B, AB or O and the Rhesus sign + or -, there are 390 other “markers”, so-called antigens.
Some occur frequently, others a little less frequently. And some can be exceptional, such as the so-called “Bombay” (one person in a million in Europe), “Rhesus zero” (around fifty people in the world) or “Vel negative” (1 in 2,500 in France).
“A blood group is considered rare if it lacks one of the 390 markers present in 99% of the general population,” Thierry Peyrard, director of the national immune reference department, tells AFP. Hematology and rare blood at the French Blood Donor Facility (EFS).
A blood type is considered rare if it affects fewer than 4 people in 1,000.
Genetic diversity
How is this rarity explained? The specificity of a blood group for a particular geographical region is the result of man's adaptation to his environment, which has shaped his genetic characteristics over the centuries.
In Africa, the cradle of humanity, genetic diversity is the greatest in the world. Certain blood groups are therefore only found in people of African or Caribbean origin.
In China, fewer than one in 1,000 people are Rh negative, compared to 15% of people in Europe. For the 2008 Olympic Games in Beijing, it was necessary to stock up on Rh-negative blood to “ensure the transfusion safety of European athletes,” recalls Thierry Peyrard.
“99.96% of the population is Vel + (one of the 390 blood type markers) and there are exceptional individuals who are Vel -. If they are immunized with an anti-Vel antibody and we give them a transfusion, it is essential to find a compatible donor, otherwise there is a risk of death,” warns the medical biologist.
In France, between 700,000 and 1 million people carry rare blood without necessarily knowing it.
We may discover one of these carriers by chance during an examination prior to a transfusion or traditional donation.
In the event of a transfusion, these people must receive blood that is as close to the body as possible, as intolerance can lead to death.
“We need maximum donor diversity in order to be able to guarantee transfusion for all patients,” emphasizes Thierry Peyrard.
A national register of sponsors of these groups lists around 18,000 donors in France.
export
With around 8,300 frozen bags of rare blood, France is “lucky to have the largest and most diversified bank in the world,” notes Thierry Peyrard. “We are also regularly contacted by our European colleagues or would like to export blood to the USA, Canada or even Australia or Japan.”
The need is particularly urgent for sickle cell anemia, a blood disease that primarily affects people of African or West Indian descent and requires regular transfusions.
Laëtitia Defoi, 33, from Martinique, has it. For several months she has been treated through transfusion exchange, in which diseased red blood cells are replaced with healthy ones. “So far I've always had the opportunity to find a compatible donor, but every month I fear there won't be one,” she tells AFP.
Yasser Osman-Ali, 28, is one of them. The Marseillais, who comes from Morocco, Comoros and Yemen and was urged to donate blood by his father, made the gesture for the first time in 2020.
“I was told that I had rare blood and that it was in great demand, that motivated me even more,” assures the young man, who has become a regular donor.