key: cord-262716-hea84shy
authors: Pourali, Fatemeh; Afshari, Mahdi; Alizadeh-Navaei, Reza; Javidnia, Javad; Moosazadeh, Mahmood; Hessami, Amirhossein
title: Relationship between blood group and risk of infection and death in COVID-19: a live meta-analysis
date: 2020-08-11
journal: New Microbes New Infect
DOI: 10.1016/j.nmni.2020.100743
sha: 
doc_id: 262716
cord_uid: hea84shy

Abstract Introduction The relationship between ABO blood group and the incidence of COVID-19 infection and death has been investigated in several studies. The reported results were controversial, so the objective of the present study is to assess the relationship between different blood groups and the onset and mortality of COVID-19 infection using meta-analysis method. Methods We searched the databases using appropriate MeSH terms. We screened articles on the basis of titles, abstracts, and full texts, and the articles that met the inclusion criteria were selected. Quality assessment was done with the Newcastle-Ottawa Scale checklist. The estimated frequency of COVID-19 infection and death in terms of ABO blood group and the overall estimate of the odd ratio between blood group with COVID-19 infection and death was done with 95% confidence interval. Results The pooled frequency of blood groups A, B, O, and AB among COVID-19 infected individuals was estimated as 36.22%, 24.99%, 29.67%, and 9.29% respectively. The frequency of blood groups A, B, O, and AB among the dead cases due to COVID-19 infection was estimated as 40%, 23%, 29%, and 8% respectively. The odd ratio of COVID-19 infection for blood group A versus the other blood groups was estimated 1.16 (CI 95%: 1.02-1.33). The corresponding figures for blood groups O and AB versus other blood groups were estimated as 0.73 (CI 95%: 0.60-0.88) and 1.25(CI 95%: 0.84-1.86) respectively. Conclusion This meta-analysis showed that individuals with blood group A are at higher risk for COVID-19 infection while those with blood group O are at lower risk. Although the odds ratio of death for AB blood group was non-significant, it was considerable.

Coronaviridae is a family of enveloped, single-stranded, positive-sense RNA viruses with the largest genome among RNA viruses (1) (2) (3) The club-shaped spike (S) proteins on their surface make them look like a crown. Other structural proteins include the hemagglutinin esterase (HE) (only found in some of them), small membrane (E), membrane (M), nucleocapsid (N), and internal (I) protein (3) . They belong to the order of Nidovirales, the suborder of Cornivirineae and are divided into two subfamilies one of them is ortocoronavirinae which is divided into 4 genera (alpha, beta, gamma, delta) (4).

Six coronaviruses causes human infections (5) including Severe Acute Respiratory Syndrome (SARS), China, 2002 (6) and Middle Eastern Respiratory Syndrome (MERS), Saudi Arabia, 2012 (7) . On late December 2019, World Health Organization (WHO) have reported cases of pneumonia with unknown etiology in Wuhan, China (8) . Further investigation of samples from patients with pneumonia isolated a novel coronavirus named 2019-nCoV (9) . WHO has declared a pandemic on 2019-nCoV or COVID-19 on March 11 th , 2020 (10) . There are more than 12 million cases and half million deaths due to COVID-19 worldwide according to Worldmeter.info (11).

There were different risk factors for mortality in COVID-19 patients including male gender, older age, diabetes, asthma, and other medical conditions (12) . Recently some studies found association between the ABO blood group and COVID-19 morbidity and mortality (13) (14) (15) (16) . ABO blood group have been also reported to be related to different infectious diseases and syndromes. Individuals with blood group O were reported to be more susceptible to Norwalk virus, and also had a significantly higher prevalence of H pylori but less susceptible for SARS (17) (18) (19) . In another study blood group A was associated with an increased risk of acute respiratory distress syndrome (ARDS) in trauma and sepsis patients (20) . A study by Lebiush et al. on influenza A (H1N1), has suggested higher seroconversion to a titer of more than 20 in blood group A and B (21) . B blood group was also reported as a risk factor for prostate and bladder cancer (22) and non-O blood groups were reported to have a higher risk of gastric cancer (23) .

As mentioned, there are articles emphasizing the hypothesis of a relationship between ABO blood group and COVID-19. In order to reach more reliable results, we have aimed to do a meta-analysis on this subject.

Meta-analysis is one of the study designs that combines the results of the preliminary studies and determine a valid estimate. Therefore, our objective is to perform a rapid systematic review and metaanalysis to discover any association between ABO blood group and COVID-19 morbidity and mortality. Note that there are limited primary evidence regarding the association between blood groups and COVID19 infection, upcoming relevant studies will be added to the results of the present meta-analysis.

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J o u r n a l P r e -p r o o f A systematic search was carried out in the available databases including PubMed, Scopus, Cochrane library, Web of Science, and also unpublished results in medRxiv. We used all MeSH terms and relevant keywords (COVID19, SARS-CoV-2 infection, COVID-19 virus disease, 2019-nCoV infection, ABO Blood Group System, ABO Factor, Blood Groups, Antigens, Blood Group). All casecontrol, cohort, and cross-sectional studies until 21 st April 2020 were included.

Inclusion criteria: 1) Studies that reported a relationship between ABO blood group and death due to COVID-19, 2) Studies that reported a relationship between ABO blood group and COVID-19 infection, 3) Studies that reported frequency of COVID-19 among different ABO blood groups and 4) Studies that reported death among COVID-19 infected people.

Exclusion criteria: case-reports and letters to the editors were excluded.

Data extracted from the primary studies included first author's name, year of publication, place of the study conduction, type of the study, sampling method, number of participants, number of COVID-19 infection, and death in each blood group, A, B, O, and AB. The required data was entered into Excel spreadsheets.

Quality assessment was performed using The Newcastle-Ottawa Scale (NOS). This checklist has three parts: selection, comparability, and exposure. The checklist scores are between 0-9. Studies with a score lower than 5 were excluded. The selection criteria for Selection was 4 in maximum, 2 for Comparability, and 3 for Exposure (24) . Quality assessment was performed by two authors independently.

Data analysis was performed using Stata ver.11. Heterogeneity between studies was assessed using Cochrane's Q test and I-squared (I 2 ) test. Standard error was calculated to assess the frequency of COVID-19 infection and death in each blood group. The overall estimate of the frequency of COVID-19 infection and death with 95% confidence interval in each ABO blood group was calculated, using random effect model. To assess the relationship between COVID-19 infection and mortality with blood group, the required data was extracted in binary tables. Using the Metan command, the random effect model, and reverse variance, the point odd ratio and 95% confidence interval was illustrated on forest plots. In these plots, the size of the square shows the weight of each study and the lines beside it show the 95% confidence interval. In the cases that confidence interval didn't include number 1, the difference was considered statistically significant.

By searching in databases, 318 studies were found. After removing duplicates, checking the titles, abstracts and full texts of the remaining articles, 314 irrelevant or duplicate papers were excluded. Quality assessment scores for the four final selected studies in the meta-analysis were above 5. The eligible studies included two case-controls, one cohort and one cross sectional studies (figure 1). Studies included were conducted in China (13) (14) (15) and United States (16) . In total, 7 data were found, J o u r n a l P r e -p r o o f from hospitals in Wuhan, Shenzhen, Xi'an, Beijing, and New York City. Totally 139,128 participants were enrolled in these studies which included 135,940 controls.

In 7 evidence included in this meta-analysis, the frequency of blood group A among COVID-19 infected people had been reported between 28.77% and 44.44%. Combining these results using random effect model (I-square:41.5%, Q:10.25, P-value:0.115), the pooled frequency of blood group A among COVID-19 infected people, was estimated as 36.22% (95% CI:32.81,39.63) (figure 2-A).

The frequency of blood group B among COVID-19 infected people had been reported in the seven evidence between 17.01% and 30.93%. Combining these results with random effect model (Isquared:79.1%, Q:28.70, P-value<0.001) the total frequency of blood group B among all COVID-19 infected people, was estimated as 24.99% (95% CI:20.35, 29.62) (figure 2-B).

In 7 evidence included in this meta-analysis, the frequency of blood group O among COVID-19 infected people had been reported from 18.18% to 45.75%. Combining these results with random effect model (I-squared:89.6%, Q:57.77, P-value<0.001), the pooled frequency of blood group O among COVID-19 infected people, was estimated as 29.67% (95% CI:22.45, 36.89) (figure 2-C).

Of the evidence included in this meta-analysis, five studies had reported the frequency of blood group AB among COVID-19 infected people varied between 3.08% and 13.68%. Combining the results with random effect model (I-squared:93.6%, Q:62.72, P-value<0.001), the frequency of blood group AB among COVID-19 infected people, was estimated as 9.29% (95% CI:4.70, 13.88) (figure 2-D).

The odds for COVID-19 infection among blood group A versus non-A blood groups was extracted from four evidence one of which was statistically significant. Combining the primary odds ratios using random effect model (I-square=47.1%, Q=5.67, P=0.129), the pooled odd ratio for blood group A was estimated as 1.16 (95% CI: 1.02-1.33) ( figure 3-A) .

The odds of COVID-19 infection among blood group B versus non-B blood groups was extracted from four evidence. it was lower in B blood group than non-B blood groups in two studies, one of which was statistically significant. Combining these results with random effect model (I-square=98.9%, Q=266.1, P<0.001), the odd ratio for blood group B was estimated as 0.65 (95% CI: 0.23-1.84) ( figure 3-B) .

The odds of COVID-19 infection among blood group O versus non-O blood groups had been reported in four evidence all of which reported lower odds of COVID-19 infection among subjects with blood group O. Three of these associations were statistically significant. By combining these results with random effect model (I-square=72.1%, Q=10.76, P=0.013), the odd ratio for blood group O was estimated as 0.73 (95% CI: 0.60-0.88) (figure 3-C).

The odds of COVID-19 infection among patients with and without blood group AB had been reported in four evidence just one of which was statistically significant. Combining these results using random effect model (I-square=80.3%, Q=15.22, P=0.002), the odd ratio for having blood group AB was estimated as 1.25 (95% CI: 0.84-1.86) ( figure 3-D) .

The odds for mortality among COVID-19 infected people with blood group A versus non-A blood group had been reported by two evidence one of which reported higher chance of mortality among patients with blood group A compare to those without. However, it was not statistically significant. Combining the results of this two evidence, applying random effect model (I-square=0%, Q=0.41, P=0.522), the odd ratio for death among COVID-19 infected people having blood group A was estimated as 1.12 (95% CI: 0.87, 1.45).

Only two studies have compared patients with and without blood group B in term of the odds of COVID-19 infection both of them showed lower odds of death among people with blood group B. but the results were not statistically significant. Combining the results of these two evidence using random effect model (I-square=0%, Q=0.01, P=0.914), the odd ratio for blood group B versus was estimated as 0.87 (95% CI: 0.65, 1.18)

The odds ratio for death of COVID-19 infected people following blood group O had been reported by two studies which both have shown negative association. However, the results were not statistically significant. Combining the results of these two evidence, applying random effect model (I-square=0%, Q=0.00, P=0.998), the odd ratio for blood group O was estimated as 0.97 (95% CI: 0.74, 1.27)

The odds ratios for death among COVID-19 infected people following blood group AB had been reported by two evidence. Both of these studies reported more chance of developing death among patients with AB group. However, they were not statistically significant. Combining the results of these two evidence, applying random effect model (I-square=65.5%, Q=2.90, P=0.088), the odds ratio for blood group AB was estimated as 1.33 (95% CI: 0.51, 3.46) (table 1).

In three studies, the frequency of death among individuals with COVID-19 infection was reported in terms of different blood groups. Combining the results of these articles, the frequency of death due to COVID-19 among patients with A, B, O and AB groups was estimated as 40% (95% CI 35-46%), 23% (95% CI 15-30%), O 29% (95% CI 16-42%), and 8% (95% CI 5-11%) respectively.

Meta-analysis of studies showed no significant association between mortality and different blood groups in COVID-19 patients. However, prevalence of death due to COVID-19 was significantly lower in blood group O in compare with other blood groups.

In this study, we found that blood group A was a partial risk factor for COVID-19 infection while blood group O was a protective factor. Moreover, B and AB blood groups were not significantly associated with COVID-19 infection.

In a study investigating ABO blood groups and susceptibility to SARS in 2005, 45 hospital staff in contact with a patient without any protective clothes were checked. They were tested for SARS-CoV IgG antibody (17) . The results showed that individuals with blood group O, were less susceptible to SARS infection however, the results were not statistically significant for blood group B and were undefined for blood group A and AB (17) . In our included studies, cases were tested with molecular methods including RT-PCR or clinical diagnostic criteria including epidemic history or clinical symptoms and clinical characteristics (13) (14) (15) (16) . Our results on the cases of SARS-CoV-2 infection were consistent with the mentioned study in the cases of SARS-CoV in blood group O.

Angiotensin converting enzyme 2 (ACE2) has been reported as the SARS-CoV receptor, and the receptor binding domain (RBD) is presented on the S proteins of the coronaviruses (19) . Guillon et al. (25) have investigated if ABO antibodies could stop interaction between SARS-CoV receptor and ACE2. They have indicated that S protein expressed by A-positive infected cells shares epitopes of A histo-blood group in vitro therefore, adhesion of S protein and ACE2 can be inhibited by anti-A natural antibody. Anti-A and anti-B natural antibodies being produced in individuals with blood group O could potentially block viral adhesion to cells which could explain lower risk of infection in them.

As SARS-CoV and SARS-CoV-2 are from the same genus (betacoronavirus) (26) and have similarities in the structure of RBD, ACE2 has been also suggested as the receptor for SRAS-CoV-2 (15) . Therefore, the same mechanism might explain the lower susceptibility of blood group O to SARS-CoV-2 as we have shown in our study. In explaining the higher risk for blood group A, lack of these antibodies can be expected, although it needs further studies to be confirmed (13) .

Individuals with blood group O have a lower Angiotensin Converting Enzyme (ACE) level while Blood group A has positive association within ACE activity (27) . ACE is an enzyme that activates angiotensin, thus; the lower level of this enzyme can reduce the risk of hypertension (28) which is a COVID-19 risk factor (29) this is another proposed mechanism for developing more severe COVID-19 disease in blood group A and less severe in blood group O (27) . Although ACE2 is the virus receptor, it can have some benefits. For example it can attenuate inflammatory response and redox stress and counter balance ACE effect and in the case of lower ACE level, it can work even more effectively (27, 30) .

As mentioned the primary receptor for SARS-CoV-2 is ACE2 (31) but like many pathogens that bind to specific terminal carbohydrates (32), SARS-CoV-2 binds to the carbohydrates that determine the ABO blood groups, which are extensively expressed in mucous membrane of respiratory tract (31, 33) . Therefore, the blood group AB has the most contact and blood group O has the least with the pathogen (31) . In addition, a study by Dai et al. (27) hypothesized that blood group A was considered to have more attachment molecules on the vascular wall by protecting P-selectin and intercellular cell adhesion molecule 1 (ICAM 1) from cleavage which increases adhesion and inflammation and can cause more severe COVID-19 disease (27) .

People with blood group O have also higher interleukin 6 (IL-6) levels (34) which is a proinflammatory cytokine that can be produced by many cells and has an important role in cell defense in acute phase (35) . However, studies showed that IL-6 is associated with COVID-19 severity as it can be part of cytokine storm (36) (37) (38) . IL-6 could have both protective role by involving in lung repair responses and also exacerbating roles in COVID-19 infection (39) . It should be noted that all of these mechanisms need to be more investigated.

In our study, there was no statistically significant association between blood group A and COVID-19 mortality but the prevalence of blood group A was significantly higher than blood groups B and AB in COVID-19 patients. The prevalence of mortality in COVID-19 patients was also significantly higher in blood group A than B and AB. Menter et al. (40) have suggested that blood group A might be associated with coagulopathies and pulmonary circulation disorder in COVID-19 patients because they genetically has higher von Willebrand factor (vWF) activity and consequently more susceptible to thrombosis.

Among COVID-19 infected individuals and the mortality cases, blood groups A and AB had the highest and lowest prevalence, respectively. However, as blood group A is the most common blood group and AB has the lowest prevalence among other blood groups in China (41) and United States (42) , countries of included studies, it could have potentially affected the results of our study.

No statistically significant association was also found between the blood group and mortality of COVID-19 in our study. As there are many factors involving in COVID-19 patients mortality including gender, age, diabetes, asthma and other medical conditions (12) , blood group has no significant effect on the mortality outcome.

Limitations of our study includes primary studies entered into the present meta-analysis have not been peer-reviewed yet. Confounding factors including diabetes, hypertension, cardiovascular diseases etc. was not adjusted in the study, because of incomplete data. More observational studies with large-scale samples and considering the confounding factors and blood groups distribution in society are being needed to conclude the association more robustly. Studies are also needed to understand the mechanisms involving protective or deteriorating effect of blood groups on COVID-19 infection.

In this meta-analysis we have found that blood group A is a partial risk factor for COVID-19 infection and blood group O is a protective factor. Blood groups B and AB were not significantly associated with COVID-19 infection. There were no significant association found between blood groups and COVID-19 patients' mortality. Further studies are being needed considering distribution of different blood groups in the society and other confounding factors concerning COVID-19 patient outcome to reach more robust results. -analysis of odd ratios for COVID -Meta - Figure 

Properties of Coronavirus and SARS-CoV-2. The Malaysian journal of pathology

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2): An Update

Advances in virus research

Epidemiology, genetic recombination, and pathogenesis of coronaviruses

Severe acute respiratory syndrome

Isolation of a novel coronavirus from a man with pneumonia in Saudi Arabia

Pneumonia of unknown cause-China', Emergencies preparedness, response. Disease outbreak news, World Health Organization (WHO)

A novel coronavirus from patients with pneumonia in China

WHO Director-General's opening remarks at the media briefing on COVID-19-11

OpenSAFELY: factors associated with COVID-19 death in 17 million patients

Retrospective Analysis of Clinical Features in 101 Death Cases with COVID-19. medRxiv

Association between ABO blood groups and clinical outcome of coronavirus disease 2019: Evidence from two cohorts. medRxiv

Relationship between the ABO Blood Group and the COVID-19 Susceptibility. medRxiv

Testing the association between blood type and COVID-19 infection, intubation, and death. medRxiv

ABO blood group and susceptibility to severe acute respiratory syndrome

Helicobacter pylori in gastric biopsies of Taiwanese patients with gastroduodenal diseases

Human susceptibility and resistance to Norwalk virus infection

ABO blood type A is associated with increased risk of acute respiratory distress syndrome in caucasians following both major trauma and severe sepsis

The relationship between epidemic influenza A (H 1 N 1) and ABO blood groups

ABO blood group polymorphism has an impact on prostate, kidney and bladder cancer in association with longevity

Mortality and cancer in relation to ABO blood group phenotypes in the Golestan Cohort Study

Critical evaluation of the Newcastle-Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses

Inhibition of the interaction between the SARS-CoV spike protein and its cellular receptor by anti-histo-blood group antibodies

Diagnostic performance of COVID-19 serology assays. The Malaysian journal of pathology

ABO blood group predisposes to COVID-19 severity and cardiovascular diseases

Angiotensinconverting enzyme inhibitors reduce mortality in hypertension: a meta-analysis of randomized clinical trials of renin-angiotensin-aldosterone system inhibitors involving 158 998 patients

Cardiovascular Diseases Burden in COVID-19: Systematic Review and Meta-analysis

Risk factors of critical & mortal COVID-19 cases: A systematic literature review and meta-analysis

How blood group A might be a risk and blood group O be protected from coronavirus (COVID-19) infections (how the virus invades the human body via ABO(H) blood group carbohydrates): figshare

Expression of ABO or related antigenic carbohydrates on viral envelopes leads to neutralization in the presence of serum containing specific natural antibodies and complement

Genetic of the ABO blood system and its link with the immune system

A genome-wide association scan on the levels of markers of inflammation in Sardinians reveals associations that underpin its complex regulation

The cytokine release syndrome (CRS) of severe COVID-19 and Interleukin-6 receptor (IL-6R) antagonist Tocilizumab may be the key to reduce the mortality

Interleukin-6 as a potential biomarker of COVID-19 progression

Detectable Serum Severe Acute Respiratory Syndrome Coronavirus 2 Viral Load (RNAemia) Is Closely Correlated With Drastically Elevated Interleukin 6 Level in Critically Ill Patients With Coronavirus Disease

Cytokine release syndrome in severe COVID-19: interleukin-6 receptor antagonist tocilizumab may be the key to reduce mortality

The Role of Cytokines including Interleukin-6 in COVID-19 induced Pneumonia and Macrophage Activation Syndrome-Like Disease

Post-mortem examination of COVID19 patients reveals diffuse alveolar damage with severe capillary congestion and variegated findings of lungs and other organs suggesting vascular dysfunction

Frequencies and ethnic distribution of ABO and RhD blood groups in China: a population-based cross-sectional study

ABO and Rh (D) phenotype frequencies of different racial/ethnic groups in the United States

J o u r n a l P r e -p r o o f