The Impact of ABO Blood Group on Clinical Outcomes and Susceptibility to COVID-19: A Retrospective Study in an Unselected Population.

BACKGROUND: ABO blood groups have been linked to susceptibility to infection with certain microorganisms, including coronaviruses. We examined the relationship between blood group and clinical outcomes in individuals infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and compared their blood group distribution to the general population. METHODS: At the inception of the pandemic, all individuals testing positive for SARS-CoV-2 in Kuwait were admitted to one designated COVID-19 hospital and enrolled in a prospective registry. Patients admitted from February 24th to May 27th 2020, were stratified according to blood group. As a control, blood groups of 3,730,027 anonymized individuals representing almost Kuwait's entire population were obtained from a national database. RESULTS: Of 3305 SARS-CoV-2 positive patients 37.1%, 25.5%, 28.9% and 8.5% were group O, A, B and AB respectively. Univariate analysis revealed no significant differences in severe clinical outcomes or death among the blood groups. However, multivariable analysis demonstrated that group A individuals had higher odds of developing pneumonia compared to non-group A (adjusted odds ratio 1.32, 95% confidence interval 1.02-1.72, p < 0.036). Compared to the general population, the COVID-19 cohort had a lower frequency of group O, equivalent frequency of A and higher frequency of B and AB. No significant difference in Rhesus D group (RhD) was found. CONCLUSION: This study supports potential involvement of the ABO blood group system in predisposing to infection with SARS-CoV-2 in an unselected population. Examination of the mechanistic link between blood group and COVID-19 and its implications on controlling the current pandemic is warranted.