Coronavirus infection and ABO blood grouping: Correlation or coincidence?

ABSTRACT

Background:

Association between the ABO blood group and patient outcomes in COVID-19 patients is still unexplored. A known association may help to understand possible risks in advance to the management of such COVID-19 patients. The present study was designed to test such association if there is any, between the ABO blood group and the severity of COVID-19 patients.

Methods:

The present hospital-based observational study was conducted at a COVID-19 dedicated tertiary care hospital in North India over a period of six months during the first wave of the pandemic in the country. Five hundred consecutive patients, who tested positive for COVID-19 using RT-PCR on oropharyngeal/nasopharyngeal swabs, admitted to the hospital were included in the study. ABO and Rhesus (Rh) blood grouping was done on leftover hematology blood samples using gel column agglutination technology. Required clinical details of patients including age, gender, clinical symptoms, comorbidities, outcomes, etc., were obtained from the patient’s case sheets.

Results:

The most common blood group was ‘B’ (42.8%) followed by ‘O’ (23.4%), and ‘A’ (22.4%) while the least common was ‘AB’ (11.4%). Rh positive was seen in 96.2% while 3.8% were negative. Baseline characteristics were comparable including length of hospital stay, duration of symptoms, and associated comorbid illnesses. The need for intensive care unit (ICU) admissions (P = 0.05) and intubations (P = 0.20) was similar across all four blood groups. Differences in the severity of COVID-19 disease and mortalities among the groups were non-significant.

Conclusion:

There was no observed association found between the ABO blood group and COVID-19 infection requiring hospitalization, ICU admission, intubation, and outcomes. However, there was a higher proportion of breathlessness and the presence of at least one comorbidity in blood group O as compared to others.

Introduction

COVID-19 emerged in late December 2019 in Wuhan, China, and has been spreading rapidly worldwide resulting in a global pandemic. The Coronaviridae is a family of enveloped, single-stranded, positive-sense RNA viruses with the largest genome among RNA viruses.[1] So far six coronaviruses have been observed to cause human infections, including severe acute respiratory syndrome (SARS), China, 2002 and Middle Eastern respiratory syndrome, Saudi Arabia, 2012.[2,3] The WHO declared a pandemic of 2019-nCoV or coronavirus disease 2019 (COVID-19) on March 1, 2020.[4]

There were different risk factors for mortality in COVID-19 patients, including male gender, older age, diabetes, asthma, and many other medical conditions.[5] Various aspects of an individual’s susceptibility to infection are being studied by many authors. Recently some studies found an association between the ABO blood group and COVID-19 morbidity and mortality.[6] In the past also, pandemics like influenza had a predilection for one or other blood groups in terms of either infectivity or severity.[7-9]

The human blood group system was first discovered by Karl Landsteiner in 1901. The locus of ABO gene is on chromosome 9 while the classification of the human blood group is determined by the presence or absence of the A and B antigens, which are carried on the surface of the red blood cells. Thus, an individual might have type A, type B, type O, or type AB blood group.[10]

The second most important classification is Rhesus (Rh) blood group. The Rh system gene is present on chromosome 1. The classification of the Rh system is determined by the presence or absence of the D antigen. Thus, an individual might be Rh positive or negative.[11]

The frequency of occurrence of ABO grouping is different among the human population due to migration and the selective advantage of particular blood groups following exposure to specific antigens thus leading to the variations observed.[12]

Several methods are available for typing of blood according to the ABO system where red blood cells carrying one or both the antigens are exposed to the corresponding antibodies. The interaction of the antigen and antibody with each other leads to the formation of visible agglutination or clumping. In gel card method, the gel column acts as a filter that traps agglutinated red blood cells as they pass through the gel column during the centrifugation of the card. The naturally occurring antibodies of the majority of group A or B individuals are mainly IgM type and a small proportion of group A and B subjects have weak IgG in addition to stronger IgM. The innate response of an individual can be modified by the blood group antigens.[13]

In the early 19^th century, during the Asian influenza epidemic, people with blood group O were more susceptible to infections of the respiratory tract as compared to non-O blood groups. Horby et al. during the 2009 influenza pandemic noted that their results were inconsistent with different studies reporting an increased risk of influenza infection with blood groups O, A, and B.[7,8] On the contrary, during the 2003 SARS epidemic, Cheng Y et al.[9] studied the relationship between the ABO blood group and the development of severe acute respiratory syndrome coronavirus (SARS-CoV) infection in a group of health care workers, who were exposed to an index SARS patient and who were not wearing any personal protective equipment; they found that blood group O participants were less likely to become infected when compared with non-O participants.

Similarly, during the present pandemic, in two recent studies, it was revealed that group A individuals were more susceptible to infection by novel coronavirus while group O individuals had less susceptibility to the infection. Exploration of the link between ABO blood grouping and COVID-19 infection is necessary as it will help in our understanding of the underlying pathophysiology which leads to the uneventful course in some while a fatal outcome in others. Also, numerous trials are ongoing which are exploring the use of convalescent plasma in the treatment of COVID-19 infection.[14,15]

In this study, we aim to find whether there is any correlation of ABO blood grouping with COVID-19 illness by comparing the course of the disease in individuals with different blood groups on various objective and subjective parameters.

Methodology

After obtaining approval from the institutional ethical committee with IEC Code 2020-215-IP-EXP-23, this observational study was conducted at a COVID-19-dedicated hospital in North India. The study was done over a period of six months between May 2020 and October 2020. Five hundred consecutive patients admitted to the hospital with a diagnosis of corona infection were included in the study. The testing for COVID-19 infection was done on nasopharyngeal and oropharyngeal swabs by RT-PCR method. Testing for blood grouping was done on the peripheral venous blood sample received for routine hematology testing after the hematology report was validated and the sample was no longer required for hematology testing. ABO and Rh blood grouping was done using a commercially available kit by agglutination technology (Biorad DiaClon, Switzerland). The processing of the sample was done in the BSL-2 laboratory situated at Rajdhani Corona hospital—SGPGIMS by trained personnel wearing the required personal protective equipment and following proper guidelines for sample processing. After the processing of the test, the result was noted and the sample was discarded in a biomedical waste bin with a double lining and labeled as COVID-19 wet waste. COVID-19 disease severity was determined as per the Ministry of Health and Family Welfare guidelines. The voluntary blood donors who donated blood at the institute from May 1, 2020, to November 30, 2020 were considered as controls for the purpose of comparison (n = 8,666).

Data analysis: Continuous variables were presented in median (interquartile range) whereas categorical variables were in frequency (%). Chi-square test was used to test the association between blood groups and demographic, clinical symptoms, comorbidities, diagnosis, and grade of hospitalization. Kruskal–Wallis H test (KWH test) was used to compare the continuous variables between four blood groups. When the P value of the KWH test or Chi-square test was significant, a post hoc test (multiple comparisons) was used using the Bonferroni test. Multivariate binary logistic regression analysis was performed to test the role of the blood groups as independent predictors of mortality after adjusting other variables. P value < 0.05 was considered statistically significant. Statistical package for social sciences, version-23 was used for data analysis.

Results

The study included a total of 500 patients admitted with COVID-19 infection. The most common blood group was B (42.8%) while the least common was AB (11.4%). Distribution of the proportion of ABO in the study patients was compared with reference studies conducted by Chandra et al. and Mohroo et al. There was almost similar distribution of blood group A in all three studies. Blood group AB was insignificantly higher in Chandra et al. whereas this blood group was observed significantly higher in Mohroo et al.[10,11] Rest for other blood group (B and O), reference studies were significantly different as compared to our study.

The distribution of COVID-19 patients according to ABO blood group along with a comparison with studies from Northern India is shown in Table 1 while the baseline characteristics of patients is shown in Table 2.

Table 1.

Distribution of COVID-19 patients according to ABO blood group along with comparison with studies from Northern India

Blood group	Study (n=500)	Ref. 1 (n=23320)	Ref. 2 (n=7822)	Ref 3 (n=8666)	P
					Ref. 1	Ref. 2	Ref. 3
A	112 (22.4%)	5,014 (21.5%)	1,877 (24.0%)	1,855 (21.4%)	0.628	0.4305	0.596
B	214 (42.8%)	8,115 (34.8%)	2,761 (35.3%)	3,024 (34.9%)	0.0002	0.0009	<0.001
AB	57 (11.4%)	3,241 (13.9%)	2,425 (31.0%)	780 (9.0%)	0.1080	0.0001	<0.001
O	117 (23.4%)	6,949 (29.8%)	759 (9.7%)	3,007 (34.7%)	0.0021	0.0001	<0.001

Ref. 1 {Chandra T et al. 2012)[11]}, Ref. 2 {Mohroo RN et al. (2021)[10]}, Ref 3 Blood donation at institute from May 1, 2020 to November 30, 2020

Table 2.

Baseline patient characteristics as per patients ABO blood groups

Variables (%)		Total (n=500)	Blood groups				P (PhT)
			A (n=112, 2.4%)	B (n=214, 42.8%)	AB (n=57, 11.4%)	O (n=117, 23.4%)
Rh	Positive	481 (96.2)	104 (92.9)	209 (97.7)	57 (100)	111 (94.9)
	Negative	19 (3.8)	8 (7.1)	5 (2.3)	0	6 (5.1)	0.12
Age (years)		5 (43, 65)	56 (43, 66)	55 (43, 62)	55 (45,63)	53 (44,66)	0.46
Gender (Female)		123 (24.6)	29 (23.6)	54 (43.9)	16 (13)	24 (19.5)	0.66
Duration of hospital stay (days)		13 (10,19)	13 (10,18)	13 (10,19)	15 (10,19)	13 (9,19)	0.04 [A-AB]
Duration of symptoms (days)		6 (3,10)	5 (2, 8)	7 (4, 10)	5 (3, 10)	7 (3,10)	0.133
Outcome (non-survivor)		106 (21.2)	19 (17)	47 (22)	10 (17.5)	30 (25.6)	0.37
No of co-morbidity #		[1, 0–2]	[1, 0–2]	[1, 0–2]	[1, 0–2]	[1, 0–2]	0.30
		[358,71.6%]	[74, 66.1%]	[158, 73.8%]	[38, 66.7%]	[88, 75.2%]
Presence of any co-morbidity		58 (71.6)	74 (66.1)	158 (73.8)	38 (66.7)	88 (75.2)	0.30
Breathlessness		225 (45.1%)	46 (41.1%)	86 (40.2%)	26 (45.6%)	67 (57.8%)	0.016 [O-A, B]

Presented in frequency (%), compared by Chi-square test. Median (Interquartile range) compared by Kruskal Wallis H test followed by Post hoc test (PhT). #Within [], n, % are presented

Most (93.6%) of the patients were symptomatic. Fever was the most common presenting symptom in 384 (76.8%) followed by cough and breathlessness in 225 (45%) each, sore throat 49 (9.8%), generalized weakness 48 (9.6%), headache 13 (2.6%), nausea and vomiting 12 (2.4%), loose stools (2.2%), loss of taste and smell sensation 9 (1.8%), each, and anorexia and cold 8 (1.6%) each. There was a statistically significant difference in the symptom of breathlessness (P = 0.016) with the highest in blood group O, followed by AB, A, and B respectively. Rest of the symptoms were similar across the blood groups (P > 0.05).

Diabetes was the most common comorbidity seen in 197 (39.4%), followed by hypertension 184 (36.8%), chronic kidney disease 60 (12%), hypothyroidism 41 (8.2%), coronary artery disease 39 (7.8%), chronic liver disease 9 (1.8%), and chronic obstructive airway disease 6 (1.2%). The occurrence of comorbid conditions was similar across all blood groups with no statistically significant difference between them.

Other underlying comorbid conditions were seen in 364 (72%) including autoimmune, abdominal pathology in 16 (3.2%) each, malignancy, cerebrovascular, hematological pathology 13 (2.6%) each, genitourinary 6 (1.2%), infective 10 (2%), morbid obesity/obstructive sleep apnoea 5 (1%), post-renal transplant 16 (3.2%).

Ours being a tertiary care referral unit receives patients with comorbid conditions. Thus, some patients with mild disease were also given hospital care in intensive care unit (ICU) owing to their high risk of developing complications of COVID-19 due to the presence of underlying comorbid conditions. The requirement for critical care was similar across the blood groups. There was no statistically significant difference in disease severity and requirement of critical care or intubation. The association of ABO blood groups with ICU admission, intubation, and disease severity is given in Table 3.

Table 3.

Association of ABO blood groups with ICU admission, Intubation and disease severity

Variables (%)	Total (n=500)	Blood group				P
		A (n=112)	B (n=214)	AB (n=57)	O (n=117)
Grade of hospitalization
ICU admission	156 (31.2)	34 (30.4)	62 (29.0)	19 (33.3)	41 (35.0)	0.05
Intubation	113 (22.6)	20 (17.9)	51 (23.8)	10 (17.5)	32 (27.4)	0.20
Diagnosis
Mild	290 (58)	65 (58)	128 (59.8)	35 (61.4)	62 (52.9)	0.90
Moderate	92 (18.4)	26 (23.2)	37 (17.3)	9 (15.8)	20 (17.1)	0.10
Severe	118 (23.6)	21 (17.8)	49 (22.9)	13 (22.8)	35 (29.8)	0.22

Chi-square test was used. P<0.05 significant

Independent predictors of the mortality: In the univariate analysis, age (P < 0.001), maximum duration of symptoms (P < 0.001), duration of hospital stay (P < 0.001), breathlessness (P < 0.001), severity (P < 0.001), and the presence of any comorbidity (P < 0.001) were significantly associated with mortality whereas ABO (P = 0.378) was insignificantly associated with mortality. For assessment of the role of ABO on mortality, multivariate analysis was performed using the above significant variable with ABO. The result showed that in the final model, ABO was not as significant whereas age, severity of the disease, and the presence of at least one comorbidity was significant predictor of the mortality after adjusting to each other. Blood groups A and AB were protected whereas B was a risk factor for mortality compared to O blood group [Table 4].

Table 4.

Independent predictors of the non-survivors among study patients (n=500)

Variable Blood group	Adjusted odds ratio			P
	Value	Lower	Upper
A	0.53	0.24	1.19	0.31
B	1.03	0.52	2.05	0.12
AB	0.73	0.27	2.01	0.94
O	Reference			0.54
Age	1.02	1.00	1.04	0.07
Severity	110.17	26.45	458.90	<0.001
Presence of any comorbidity	3.99	1.63	9.81	0.003

Multivariate binary logistic regression analysis was used. P<0.05 significant

Discussion

The present study revealed no association between ABO blood group and COVID-19 infection and disease severity.

ABO and requirement for hospitalization due to COVID-19

Review of literature reveals studies done during the COVID-19 pandemic to study the association of blood grouping with COVID-19. Research conducted during the earlier outbreaks of severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1) by Guillon et al.,[16] 2008 and during the earlier days of current SARS-CoV-2 pandemic by Zhao et al. (2020)[14] on patients tested positive for COVID-19 found that blood group A individuals were at a higher risk for acquiring COVID-19 whereas blood group O was associated with a lower risk for the infection compared with non-O blood groups. They attributed it to the presence of anti-A antibody in people with blood group O or B and postulated that the anti-A antibody hinders the binding of the virus and the receptor for angiotensin converting enzyme 2 (ACE2) found in various cells of the body. This receptor for ACE2 cells has been studied as a possible mechanism for the entry of COVID-19 virus into the human body. Likewise research by Hoiland et al., and Pourali F et al. had similar findings.[17-20] Contrary to this no association was found between ABO blood group and COVID 19 in the present study as also observed in study by Barnkob et al.[21] and Bhattacharjee et al.[22]

ABO and COVID-19 symptoms

COVID-19 has a wide range of presentations ranging from asymptomatic infection to ARDS. Overall most frequently appearing symptom in this study was fever seen in 76.8% of patients followed by cough and breathlessness seen in 45% of patients, each. As also observed by Wu Y et al.[23] fever was the more common symptom in individuals with blood group A while cough was more common in AB blood group individuals. However, breathlessness was more common in individuals with blood group O.

ABO and COVID-19 severity

On comparing the severity of illness in the patients belonging to different blood groups and the need for critical care in ICU and intubation there was no difference observed as also seen by other authors.[24-26] Contrary to this, a study by Hoiland et al.[17] found that a higher proportion of COVID-19 patients with blood group A or AB required mechanical ventilation and had a longer ICU stay (13.5 days) compared with patients with blood group O or B. Also, the author attributed the finding to reduced levels of factor VIII and von Willebrand factor in group O individuals, which may be responsible for the protective role of blood group O against COVID-19-associated coagulopathy which has been found to have a pivotal role determining the outcome.

Furthermore a genome wide association study of severe COVID-19 patients showed that those with blood group A had a higher risk of severe disease, while blood group O had a protective effect but no difference was observed among patients requiring any form of mechanical ventilation.[22,23,27] Also a study in Eastern India found individuals with blood group A in addition to more critical care needs were found to have higher viral load on testing.[28]

Effect of comorbidity as a confounder in ABO and COVID-19

Not only the presence but also the number of comorbidities affects COVID-19 disease severity and outcome. Majority (71.6%) of the patients had one or the other associated comorbidity. After nullifying the effect of comorbidity as a confounder there was no predilection of any ABO blood group for increased disease severity or morbid outcome.[29]

ABO and COVID-19 mortality

No association was found between mortality and ABO blood group. But, in a similar study by Wu BB et al.[30] who compared blood groups with mortality found that the rate of mortality was higher in individuals with blood group A and AB while the rate was comparable in individuals with blood group B. But, Pourali F et al.[18] and Barnkob et al.[21] in their study did not find any correlation between mortality and blood grouping.

Rhesus factor and COVID-19

Association of Rh factor and COVID-19 was not studied in detail in the present study. Zietz et al. studied the relation between Rh status and COVID-19 illness. They stated that Rh-negative blood type was supposed to have a protective effect on the risk of contracting infection of COVID-19.[15] Also, if infection was contracted Rh-negative individuals were less likely to require critical care/intubation and had a lesser chance of morbid outcome. The patients enrolled in the current study were predominantly Rh positive (96.2%) and tested positive for COVID-19. This might be attributed to the fact that Rh-positive blood groups are more commonly found (94.1%) as compared with Rh-negative individuals.[15,25]

Conclusion: There was no observed association between ABO blood group and COVID-19 infection requiring hospitalization, ICU admission, intubation, and morbid outcome.

Strength and Limitations: The study included small sample size from a single center and was of observational type. The strength lies in the large sample size and collection of real time data indicating the severity of the disease. The confounding effect of ethnicity and race cannot be ruled out. Also as most of the patients had other underlying comorbid conditions, all the intubations, ICU admissions, and deaths cannot be attributed solely to COVID-19 infection or complication.

Summary

The present hospital-based observational study was conducted at a COVID-19-dedicated tertiary care hospital in North India over a period of six months during the first wave of the pandemic in the country. It included 500 COVID-19 patients. The most common blood group was “B” (42.8%) followed by “O” (23.4%), and “A” (22.4%) while the least common was “AB” (11.4%). Rh positive was seen in 96.2% while 3.8% were negative. Baseline characteristics were comparable including length of hospital stay, duration of symptoms, and associated comorbid illnesses. The need for ICU admissions (P = 0.05) and intubations (P = 0.20) were similar across all four blood groups. Differences in severity of COVID-19 disease and mortalities among the groups were non-significant.

There was no observed association found between the ABO blood group and COVID-19 infection requiring hospitalization, ICU admission, intubation, and outcomes. However, there was a higher proportion of breathlessness and the presence of at least one comorbidity in blood group O as compared to others.

Take home message from this manuscript

• ABO blood group has been found to have an influence not only on susceptibility to certain infections but also in the development of severity.

• No association was found between ABO blood group and COVID-19 infection with regard to requirement for hospitalization, ICU admission, intubation, or morbid outcome.

Novelty/new knowledge emerging from this manuscript

• No association was found between ABO blood group and COVID-19 infection with regard to requirement for hospitalization, ICU admission, or intubation.

• No association was found between ABO blood group and morbid outcome in COVID-19-infected patients.

How this paper is relevant to the practice of primary care physicians

• ABO blood group has been found to have an influence not only on susceptibility to certain infections but also in the development of severity.

• Most individuals in the general population are aware of their blood group. It can be used in triaging patients.

• If the blood group is not known then determination can be done within an hour even in resource-limited settings.

• In the present study there was no observed association found between the ABO blood group and COVID-19 infection requiring hospitalization, ICU admission, intubation, and outcomes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.