A new, preliminary study has found correlations between blood type and the likelihood of being hospitalized with COVID-19. According to the authors, people with type A blood might be more at risk than those with other blood types.

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A new, preliminary study asks whether blood type might help predict COVID-19 risk.

Researchers from the Southern University of Science and Technology, in Shenzhen, China — in collaboration with colleagues from other Chinese institutions — have recently conducted a study assessing the potential relationship between blood type and hospitalization due to SARS-CoV-2 infection.

Their study is preliminary and has yet to be published in a peer-reviewed journal, which means that other experts have not yet had a chance to assess the researchers’ methodology and findings.

However, they have made their study paper available online in preprint form.

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The researchers looked at blood group distribution among 2,173 individuals admitted to hospitals with COVID-19, the disease caused by the new coronavirus. The people each received care at one of three hospitals in Wuhan, China, or Shenzhen.

The team then compared the patients’ blood group distribution to that of a group representative of the general population — totaling 3,694 people — in Wuhan.

The researchers found that the proportion of people with blood type A was significantly higher among the group hospitalized with COVID-19 than among the general population.

They also found that the proportion of people with blood type O was significantly lower among the group with COVID-19 than among the general population.

Based on these findings, co-first study author Jiao Zhao and colleagues report that “People with blood group A have a significantly higher risk for acquiring COVID-19, compared with non-A blood groups, whereas blood group O has a significantly lower risk for the infection, compared with non-O blood groups.”

It is important to stress, however, that the researchers refer to the risk of needing hospitalization because of COVID-19, rather than the risk of contracting the virus that can lead to the disease.

This is because the team only looked at data from individuals whose symptoms were severe enough to require hospitalization, not those with mild symptoms that responded to home care.

But does this really mean that people with type A blood have added cause for concern, while those with type O can exhale in relief?

Experts not involved with the research have commented on the findings, explaining that the study does not demonstrate a causal relationship between blood type and susceptibility to being hospitalized with COVID-19.

Sakthi Vaiyapuri, Ph.D., an associate professor of cardiovascular and venom pharmacology at the University of Reading, in the United Kingdom, emphasizes that people with type A blood should not worry because of this preliminary study’s results.

“There is little evidence to substantiate any claim that there [is] any more than a coincidental correlation between blood group ABO and susceptibility of contracting COVID-19,” he says.

“There are far too many parameters that cast doubt over the credibility of [the researchers’] claims, which — worse still — are not mentioned in a non-peer reviewed preprint study,” Vaiyapuri cautions.

“Without establishing causal links between [the coronavirus] and ABO blood group antigens, it’s difficult to understand this conclusion, which might be purely coincidental. Importantly, people should not panic about these results, as, clearly, further scientific research is required to substantiate these claims.”

– Sakthi Vaiyapuri, Ph.D.

Moreover, the current study, which included data only from very specific populations in China, did not account for some confounding factors, such as that blood group distribution varies by country.

However, if further research confirms the study’s findings, they could help medical professionals identify people most at risk of requiring hospitalization due to infection with the new virus.

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