DISCUSSION
A total of 1667 Covid-19 patients were included in our study. In
Covid-19 patients, it was observed that the ratio of blood group A and
AB was higher than in the healthy control group, and blood group O had a
lower ratio. The statistical analysis showed that there was a very
significant increase in the number of individuals with blood group A in
Covid-19 patients compared to healthy individuals, almost a significant
increase in the number of Covid-19 patients with blood group AB, and a
very significant decrease in the number of Covid-19 patients with blood
group O (P <0.001, P=0,052 and P<0.001,
respectively).
The ABO blood group system basically contains A and B antigens and their
corresponding antibodies. The gene coding the antigen is located on
chromosome 9q34.1-34.2. It consists of A, B and O alleles, and there are
4 phenotypes (A, B, O, and AB blood groups). 11,12Differences in blood group antigen expression may increase or decrease
host susceptibility to many infections. Blood group antigens can play a
direct role in infection by serving as receptors and / or cofactors for
microorganisms, parasites, and viruses. In addition, many blood group
antigens facilitate intracellular uptake, signal transmission or cell
adhesion through the organization of membrane microdomains. Blood group
antigens may alter the natural immune response to
infection.13 Since the beginning of the Covid-19
pandemic, many studies have been conducted on this subject. Zhao J YY et
al. examined the ABO blood group distribution in 2,173 Covid-19 patients
and showed that the frequency of blood group A was higher in Covid-19
patients than that of non-A blood groups and found that the blood group
O was associated with a lower risk for infection compared to the non-O
blood groups.14 Yuqin Wu et al. found similar results
in their study on 187 Covid-19 patients and H. Goker et al. in their
study on 186 Covid-19 patients.15-16 In the study
carried out by E. Arac et al., there was no significant difference
between ABO blood groups, but strong significance was found in Rh
system.3 We believe that this study had some
limitations due to the fact that PCR-negative patients were also
included in the study, the number of cases was small, the study was
conducted at the beginning of the pandemic, and the prevalence of
Covid-19 in some circles, especially among some families, rather than
across community. In our study, we found that blood group A was more
frequent than in community and statistically significant, blood group O
was less frequent than in community and statistically significant, and
blood group AB was more frequent than in community, but it was not
significant. We think that blood group A is more susceptible to Covid-19
and blood group O is protective.
When Covid-19 patients in need of intensive care and deceased patients
were compared, blood groups were shown to have no significant effects on
intensive care and mortality. ABO blood groups have been associated with
cardiovascular diseases before.17 It is known that
thrombotic risks decrease significantly in blood group O compared to
non-O blood groups17,18. Studies have shown that
microthrombosis that develops in Covid-19 infection in the pulmonary
vascular bed contributes significantly to acute respiratory syndrome;
therefore, the use of prophylactic anticoagulants is also included in
the guidelines.19,20 There are opinions arguing that
the protective effect shown in blood group O is based on this
phenomenon21. In this study, we found that blood
groups were not statistically significant in predicting the patient’s
need for intensive care and mortality.
In conclusion, we believe that our study is important because it is a
study with the highest number of Covid-19 patients diagnosed by PCR,
which examined the blood group and Covid-19 relationship in our country.
Our study has found that having blood group O may be protective, that
blood group A may have greater susceptibility to the disease, but this
does not affect the course of the disease and is not associated with
mortality. We want to emphasize that the most important and easiest way
to avoid Covid-19, regardless of the risk factor and the facilitating
factor, is to maintain social distance, hand hygiene and use of masks.
Although there is no significant difference between blood groups and
intensive care and mortality, it can be concluded that individuals with
blood group A should take stronger and stricter measures and Covid-19
patients with blood group A should be monitored more closely. Larger,
multicenter and prospective studies should be conducted to determine the
relationship between blood groups and Covid-19 and the protective role
of blood group O.