whether or not they have certain molecules or proteins — called antigens — on the surface of their red blood cells, according to the National Institutes of Health.
Two of the main antigens used for blood typing are known as “A antigen” and “B antigen.” People with type A blood only have A antigens on their red blood cells and those with type B blood have only B antigens. Individuals with type AB blood have both; people with type O blood have neither.
Another protein, the “Rh factor” – also known as the “Rhesus” system – is also present or absent on red blood cells.
A person’s blood type is designated as “positive” if they have the Rh protein on their red blood cells, and “negative” if they don’t have this protein.
Even still, a second smaller study also published this week seems to boost those findings. Researchers in Canada looked at data on 95 Covid-19 patients in Vancouver from February to April.
All were sick enough to be hospitalized in intensive care units.
Again, researchers found differences in blood types. This time, certain types appeared to be associated with worse outcomes.
“A higher proportion of Covid-19 patients with blood group A or AB required mechanical ventilation and had a longer ICU stay compared with patients with blood group O or B,” the study authors wrote.
Types A and AB were also more likely to need a type of dialysis that helps the kidneys filter blood without too much pressure on the heart.