According to the new study published in the New England Journal of Medicine, a link was found between a particular blood type and the genetic variables, and the COVID-19. The authors were mainly focused on the usefulness of their gene-related findings, which laid emphasis on the formations of clusters of genes around a specific chromosome in severe cases of COVID-19, whereas the media was focused on the blood-type findings. A study was conducted in which 1500 Italian and Spanish Covid-19 affected patients were kept under observation. It was concluded that the infection was less common in the patients with the blood type O, whereas it was more common in the patients with blood type A. The commonality of the infection found in the people with blood type B was found in between the two.
The results of the blood-type study were found to be closely similar to an earlier study paper from China according to which the Type A blood group people were at higher risk of getting infected than the Type O blood group people. Tom Karlsen, MD, Ph.D., Professor of Internal Medicine at the University of Ohio, and the co-author of the new study confirmed the existence of other studies, which proves the associative relationship between the two, and this has been identified for SARS as well.
Both SARS and the COVID-19 virus stem from a genetically similar coronavirus. Therefore, it completely makes sense that if for one of the diseases a certain blood type is associated with the lower risk, then it might hold for the other disease as well. Like these, there are several other similar relations between blood type and infectious diseases that exist for other group of diseases. For instance, O-type blood groups are associated with lower chances of contracting malaria but suffer through severe cases of cholera.
These new findings related to the getting infected and the blood type surely gave some relief to the O- type blood group people but created chaos in the minds of the A-type blood group people. But some of the experts are not entirely convinced with the study and say that these findings are 100% questionable and that they might even be false or incorrect.
Laura Cooling, MD, a Professor and the Associate Director of the Transfusion Medicine at the University of Michigan, says that she been receiving mails from many people asking her if they need to get blood-typed or not to which her constant response is NO!
Laura Cooling, along with some other American Researchers, have been studying and looking after the study of the blood-group data since the early days of the outbreak and have come up with the view that they haven’t found the relations meaningful. According to her, blood-type wholly cannot be considered as the deciding factor as other risk factors like obesity, heart diseases, hypertension, etc., also play a major role in deciding the proneness of a person of getting infected by the virus.
Walter Dzik, MD, a Pathologist at the Massachusetts General Hospital who conducted studies to determine the relationship between the COVID-19 and the ABO blood-types have also presented similar views to Laura Cooling expressing his denial towards the correctness of the study expressing the relation between the blood type and the risk of getting infected.
To clear this doubt and to understand it better, the relation between the blood group and the infectious pathogens must be understood properly by all.
The Connection Between Blood Type and Infection Risk
Various molecules of protein and sugars are coated over the entire surface of the Red Blood Cells. This layer of molecules supports the walls of the blood cells, helps the cell in performing its function, assist in chemical reactions and other activities. Hundred of the blood-cell molecules are present on the surface and these coating of molecules differs from one person to another. This coating is called the ‘Antigens’ as they elicit a response from the immune system of the body.
Experts have these blood molecules together, which formulates the blood group of a person. One such category of blood group is the ABO blood group, which takes certain specific sugars into account that decorate the Red Blood Cells. Various versions of a single gene determine the presence or absence of these sugars on the red blood cells which in turn help in determining the blood type of the person, that is, if the person is blood-typed A, B or AB or O. In people having O-type blood group, that particular single gene is non-functional and mutated in nature.
Now the question arises, What relation does the blood group hold with the novel Coronavirus disease or any other infectious disease? According to James Fleckenstein, MD, Professor of Medicine and Molecular Biology at the Washington University School of Medicine in St. Louis, the possibility of these associations can be linked to the presence of the antigens and immune antibodies in each blood group. He adds further that the people with different blood groups can have their immune system respond differently to the pathogens like SARS and COVID-19 virus.
James Fleckenstein says that the blood groups can act as receptors for the pathogen or the proteins they produce to bind. There are certain glycans and sugars which are required by the pathogens to attach to its target host. A similar coating of protein and the sugar molecules present on the surface of the Red Blood Cells are present on the mucosal surfaces as well, such as the walls of intestines or lungs. This makes it an easy target and an excellent surface for the pathogens to bind with its host (virus binding) and undergo the process of viral proliferation.
“However, it is very important to keep in mind that the blood group alone can’t be the only risk factor that predisposes a person towards getting infected. Other factors like obesity, hypertension, heart disease, or other such factors are responsible too.”
Certain other potential explanations also exist for the same. There are certain researches which explain the linkage of COVID-19 to abnormal blood clotting and regarding the role of the blood-group antigens over coagulation of blood.
Another question that pops up in mind is Why such blood-based differences exist in human beings? One theory is that these differences in the blood-group will ensure that every person doesn’t fall into the trap of any form of plague or pandemic hitting the world. In areas, where a certain type of disease or infection has been prevalent for a long time, people with infection-fighting blood groups have been found. James Fleckenstein talks about the situation in the Ganges River Delta, where fewer people with blood type O are found and one of the primary reasons identified for this is the selective pressure from Cholera. Similar incidences can be found all around the globe. This may be due to the fact that the people with certain blood-types who were able to survive through the situation were able to pass on their genes to future generations.
There is a number of reasons for the doctors and the researches to conduct their researches thoroughly on the relation between blood group type and SARS-CoV-2. However, according to Harvard’s Dzik, the findings of the study till date related to linking type O blood group people with a lower risk of getting infected by COVID-19 is most likely to be inaccurate.
Dzik has put light on the fact that even though blood type O (the protective blood type) people are more common and prevalent among the African and Latino Ancestry than the Caucasians, COVID-19 has affected them fiercely. According to data, 57% and 50% of Hispanics ad Blacks are type O whereas only 45% of the Caucasians are type O. Hence, it is evident that the reported association of the blood-type and the risk of getting infected by COVID-19 is incorrect right from the beginning.
“Flawed” Findings?
Concerning the study published in the NEJM, Dzik raises the point of it potentially being a methodology problem. According to him, the problem is related to the choice of the Comparison Group. This was in reference to conducting the study and generating the results on the basis of comparing the non-patient group against the group of people affected with COVID-19 disease.
In the NEJM study, most of the people within the control group were blood donors. It is a known fact that the ABO distribution does not represent the entire general population among the group of blood donors. It is the Group O blood type people who are preferred for donating blood as their red blood cells can be used by any recipient. So, if the people with the blood-type O were over presented on the Control Group side, then they will be under presented on the Patient Group side, and that is what the results of the study indicated.
Laura Cooling from the University of Michigan has found yet another flaw in the methodology of conducting the study. The blood types were being inferred based on the three genetic (single nucleotide polymorphisms). The red blood cells of the patients were never typed physically. This means that the assessment of the blood types was done on the basis of minute pieces of DNA information which though imperfectly correlates with the blood type. Due to this, the study team can incur the common mistake of overcounting the A’s and the B’s and undercounting the O’s.
Some of these drawbacks of the NEJM study was highlighted in the research paper by the authors of the study as well. Karlsen from the University of Oslo says that they were well aware of the problems whilst conducting the study and that they had done every effort that they could to tone down the effect of the biasness based on conducting the study on the selected donor pool. He also agreed to the puzzling nature of the ABO blood group and says that anyone and everyone is welcome to do the follow-up study on his and his co-author’s findings.
If the research on the blood-type pans out it doesn’t hold much value for any average person out there. According to these studies, the Type O blood group are at a reduced risk of getting infected and not at zero risks of getting infected. For instance, a Chinese study pointed out that amongst a whole lot of COVID-19 infected people, 26% were Type O blood group people, whereas 34% were Type A blood group of people. Karlsen says that people with blood type O are also highly predisposed to getting infected with the COVID-19 disease as any other person with blood-type A or B. Any further insight of this data is based on the results of the further studies and not on clinics.
Laura Cooling suggests that taking other aspects of the study into account, like the data related to the COVID-19 involved gene clusters, can be proven to be helpful. But for now, the people need to keep themselves away from the blood-type hype. Having an O-blood group doesn’t mean that the person has now had that “S” titled on their chest and has become the Superman and that it won’t get you. If there is any sort of protection that these O-type people have, it will become weak over time if proper precautions are not taken.
REFERENCES:
https://www.nejm.org/doi/full/10.1056/NEJMoa2020283
https://www.ncbi.nlm.nih.gov/books/NBK100894/
https://www.medrxiv.org/content/10.1101/2020.03.11.20031096v2
https://jamanetwork.com/journals/jama/article-abstract/200582
https://www.facs.org/media/press-releases/2020/blood-clotting-051520
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