Association between blood groups and COVID-19 outcome in Iranian patients

Aim: Many factors have been speculated to explain the COVID-19 complex clinical phenotype. Due to the inconsistent data published on blood groups and COVID-19, we conducted a study on Iranian patients to further assess this association. Materials & methods: This retrospective study was conducted on data collected from confirmed COVID-19 hospitalized patients during March and December 2020 in a referral hospital for COVID-19, 5 Azar Hospital, Gorgan, north of Iran. A total of 1554 confirmed COVID-19 cases were enrolled in the study with blood group (ABO and Rh), demographic, and clinical data available. Results: Of 1554 patients, 1267 and 287 cases had recovered and deceased (due to COVID-19) outcomes, respectively. Most of the cases had O+ (29.6%), the least number had AB- (0.5%), and most of the deceased cases had O+ blood types (31.4%). Logistic regression analysis revealed that groups A- and B- had higher and groups B+, AB+, O+ and O- had lower odds of death than the A+ group. Conclusion: This study indicates that blood types may be related to the clinical outcome of COVID-19. Further studies with a large cohort for multiple people are required to validate this association.

The association between blood groups and susceptibility to some viral infections has been well established [6][7][8][9][10][11]. The blood group antigens are cell-surface glycoproteins present principally on erythrocytes that may affect infectious diseases [12]. During the current pandemic, several studies have investigated the association of blood groups and COVID-19 [13][14][15][16][17][18]. Some studies suggested that patients with blood group A are more susceptible to severe infection, but there are other controversial results [19][20][21][22][23][24]. More studies are needed to confirm the association between blood grouping and COVID-19 susceptibility and severity. Here, we investigated the association between blood groups (ABO and Rh) and COVID-19 outcomes in Iranian hospitalized patients.

Materials & methods
This retrospective study was conducted on data collected from patients hospitalized during March and December 2020 in a referral hospital for COVID-19, 5 Azar Hospital, Gorgan, north of Iran. A total of 1554 confirmed COVID-19 cases were enrolled in the study with blood group (ABO and Rh), demographic, and clinical data available. All COVID-19 patients had been confirmed by reverse transcriptase real-time PCR assay targeting the SARS-CoV-2 nucleoprotein (N) and ORF1ab genes (Pishtazteb, Iran). Data such as blood group, gender, age, hospitalized ward and disease outcome was collected from the patients' case report forms. Because the frequency of participants in different age groups was different, the patients were classified into different age groups according to the literature. The patients were also classified into different hospitalized wards. Two outcomes, recovered and deceased (due to , were examined in this study. All of the patients were from Golestan Province and had the same geographical origin. Analyses were performed using SPSS version 25.0 (IBM Corp., NY, USA). Data were presented in proportions. We performed a chi-square test to compare the proportion of blood groups, age group, sex and hospitalization wards between the recovered and deceased groups. Multiple logistic regression was computed to assess the odds of death (dependent variable). Independent variables included the blood groups, age group, sex and hospitalization wards. The reported p-value is two-sided, and p-values less than 0.05 were considered statistically significant.  Table 1. In this study, there was no significant association between gender and the outcome of COVID-19. The data showed a significant association between age and the outcome of the disease. The number of COVID-19 cases and deaths gradually increased with age, so the odds of the deaths were higher in the age group over 60 years compared with the reference group. We found a significant association between hospitalization ward and outcome of the disease. The odds of death were higher in those hospitalized in the ICU/CCU/emergency wards than in the infectious disease group. Most of the COVID-19 cases in this study had O+, the least had AB-and most deaths had O+ blood types. Logistic regression analysis revealed that odds of death in group A-versus A+ were 1.81-times higher, though it was not significant. Blood type B+ had lower odds of death than A+. Patients with type B-, 3.8-times more likely for COVID-19 death than the A+ blood group. Patients with the AB+ group had lower odds of death than the A+. Finally, group O+ and O-had a lower odds of death than the A+ blood group. The details association of sex, age, blood group and hospitalization wards of COVID-19 patients with risk of death are presented in Table 2.

Discussion
This study indicates that blood types may be related to the clinical outcome of COVID-19. The main findings of this study are: no significant association between gender and outcome of COVID-19, a significant association between age and the outcome of the disease, a significant association between hospitalization ward and outcome of The O+ blood group had the lowest risk of having severe symptoms, and A+ individuals were the most vulnerable when exposed to the virus [29] Abdollahi et al.  There was no differences between distribution of Rh (D) +ve type and Rh (D) -ve in severe, moderate and mild patients [19] AKI: Acute kidney injury; ARDS: Acute respiratory distress syndrome; CRRT: Continuous renal replacement therapy; ICU: Intensive care unit.
COVID-19 and blood groups A-and B-have higher and groups B+, AB+, O+ and O-have lower odds of death than the A+ group (Table 1 & 2). Previous studies demonstrated that male cases have an increased risk of death compared with females [25]. However, in this study, there was no significant association between gender and the outcome of COVID-19. Studies also demonstrated that age could be considered as a death-associated risk factor for COVID-19 [3,26]. Most of the data in this context agree that the infection and death were mostly observed in cases with advanced ages. Our data showed a significant association between age and the outcome of the disease. The number of COVID-19 cases and deaths gradually increased with age, so the odds of the deaths were higher in the age group over 60 years. This finding might be expected because elderlies tend to have a higher prevalence of comorbidities such as diabetes, heart disease, hypertension, chronic respiratory diseases and they have a reduced immune response. A significant association between hospitalization ward and outcome of the disease was found, and also odds of death were higher in those hospitalized in the ICU/CCU/emergency wards. This finding also might be expected because critically ill COVID-19 patients are hospitalized in these wards.
Regarding blood groups, our data showed that odds of death in the group A-versus A+ were 1.81-times higher, and patients with type B-, 3.8-times more likely for COVID-19 death than the A+ blood group. However, other blood groups such as B+, AB+, O+ and O-had a lower odds of death than the A+ blood group. It is not yet clear which blood type is most likely to be susceptible to COVID-19. Some studies considered that people with blood type A to be the most susceptible to the disease, and people with blood type O are less likely to develop the disease [13][14][15][17][18][19][20]24,. But other studies reported conflicting results [22,23,56,57], and some did not find a significant relationship between blood type and COVID-19 [16,21,[58][59][60]. Moreover, studies reported that individuals with Rh-blood type had a lower risk of infection, intubation and death, and cases with Rh+ were more sensitive to COVID-19 [24,[27][28][29]56,57]. However, a study from Iran did not find any relation between COVID-19 and Rh type [30]. Another study in Turkey also did not report a relationship between Rh blood groups and any impact on the rate of hospital admission, ICU stay, mechanical ventilation support and case fatality rate [31]. The literature studies regarding the association between blood types and COVID-19 are summarized in Table 3.
The discrepancy between studies may be due to the different sample sizes, heterogeneity of ABO between populations or geographical areas, differences in genetic background and differences in viral strains. Variation between blood group phenotypes in countries and different genetics may affect heterogeneity of COVID-19 clinical phenotypes [21,61]. Susceptibility to SARS-CoV-2 infection and ABO blood system might be for some reasons: blood group O patients had natural anti-A and anti-B antibodies that could be partially protective against SARS-CoV-2 virions, carbohydrate-carbohydrate interactions, which could maximize or minimize the virus spike protein binding to the host cell, furin levels might be reduced in blood type O individuals, so the infectivity of virus is reduced, the levels of C-reactive protein and alkaline phosphatase appear to be higher in blood group A individuals in comparison with blood group O and microbiota trigger the synthesis of anti-A and anti-B antibodies [61,62].

Conclusion
Finding high-risk groups for severe infection and death are important to manage the current pandemic disease.
The results of such studies could lead to individuals with a higher risk of severe infection being vaccinated earlier or monitored more closely and treated earlier. Together, these findings suggest that the blood group may interplay with susceptibility to SARS-CoV-2 infection and clinical course of COVID-19; however, the mechanism(s) is subjected to speculations. The limitation of this study was the small sample size, and further studies with a large cohort for multiple people are required to validate this association.

Summary points
• Due to the inconsistent data published on blood groups and COVID-19, we conducted a study on Iranian patients to further assess this association. • A total of 1554 confirmed COVID-19 cases were enrolled in the study with blood group, demographic and clinical data available. • Of 1554 patients, 1267 and 287 cases had recovered and deceased outcomes, respectively. • Most of the cases had O+ (29.6%), the least number had AB-(0.5%), and most of the deceased cases had O+ blood types (31.4%). • Logistic regression analysis revealed that groups A-and B-had higher and groups B+, AB+, O+ and O-had lower odds of death than the A+ group. • Our findings indicate that blood types may be related to the clinical outcome of COVID-19.
• Further studies with a large cohort for multiple people are required to validate this association.

Author contributions
A Tahamtan and AA Ayatollahi conceptualized and designed the study. B Aghcheli, A Amini, H Nikbakht and P Ghassemzadehpirsala collected data. A Rajabi and B Aghcheli analyzed the collected data. B Aghcheli and E Behboudi drafted the manuscript. All authors evaluated and edited the manuscript and have read and approved the final manuscript.