Blood groups may be a key factor in making people susceptible to developing severe respiratory problems during a Covid-19 infection, according to a study of 1,600 patients in hot spot cities in Italy and Spain that suggested those with blood group A positive were most at risk while those with O were protected to some degree.
The study, published on preprint server medRxiv, is yet to be peer reviewed. The researchers carried out a genome-wide association analysis to determine what genes were common among those that developed a severe respiratory illness after being infected by Sars-Cov-2.
The researchers detected at least a couple of significant “associations”, including one that “located at the ABO blood group locus and a blood-group-specific analysis showed higher risk for A-positive individuals and a protective effect for blood group O”, they said in the paper.
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The ABO blood group locus refers to a set of genes that determine which blood group an individual has.
The study could offer scientists more insight into why the disease behaves unpredictably across humans: the symptoms range from being virtually non-existent, resembling a flu, or, in most severe cases, leaving people unable to breathe.
“Respiratory failure is a key feature of severe Covid-19 and a critical driver of mortality, but for reasons poorly defined affects less than 10% of Sars-CoV-2 infected patients,” the researchers said.
{{/usCountry}}“Respiratory failure is a key feature of severe Covid-19 and a critical driver of mortality, but for reasons poorly defined affects less than 10% of Sars-CoV-2 infected patients,” the researchers said.
{{/usCountry}}The variations in symptoms have often defied age and gender trends that largely suggest older men may be more vulnerable to the virus. There have been a significant number of young people who have succumbed to the illness.
The study covered 1,610 patients from hot spot cities in Italy and Spain who had developed severe symptoms after contracting the virus. The team of researchers included clinicians at the European Covid-19 epicentres in Italy and Spain and available German and Norwegian scientists. The analysis also used samples from 2,205 blood donors with no evidence of a Covid-19 infection for the genomic comparison.
The researchers noted that their findings corroborate publicly available results from the Covid-19 Host Genetics Consortium, where similar associations have been noticed among Covid-19 affected cases versus a population-based sample.
The findings in connection with the blood groups also associate with another Covid-19 symptom seen among people who develop serious illness: blood clotting. “Genetic variation at the ABO locus has previously been associated with a number of procoagulant markers such as von Willebrand factor and Factor VIII, and the potential relationship between our genetic findings and the significant coagulopathy that is observed in severe Covid-19 warrants further attention,” the researchers wrote.
Genome-wide association studies are among the key strategies researchers deploy to understand a disease. The genome, simply put, determines how a human body is made up at a cellular level and the functions it carries out, whether to make or repair new cells.
These findings could help efforts to tailor therapies that at present are only mildly effective in treating Covid-19 patients.
“There is usually a strong relationship between blood group and disease. But it is very difficult at this stage to determine this particular correlation unless there is a very huge study,” said Dr RN Makroo, a specialist in molecular biology. “The distribution of blood groups in population also needs to be accounted for,” he added.