Relationship between ABO Blood Group Distribution and COVID-19 Infection in Patients Admitted to the ICU: A Multicenter Observational Spanish Study.

Since the beginning of the COVID-19 pandemic in December 2019, a relationship between the ABO blood group type and the novel coronavirus SARS-CoV-2, the etiological agent of COVID-19, has been reported, noting that individuals with the O blood group are the least likely to be infected. Spain is one of the most badly affected countries worldwide, with high rates of patients diagnosed, hospitalized, and deceased due to COVID-19 infection. The present study aimed to analyze the possible relationship of ABO in COVID-19 patients hospitalized in different Spanish centers during the first wave of the COVID-19 pandemic, for which the ABO group was available. Physicians from the transfusion services of different Spanish hospitals, who have developed a multicenter retrospective observational study, were invited to participate voluntarily in the research and 12,115 patients with COVID-19 infection were admitted to the nine participating hospitals. The blood group was known in 1399 cases (11.5%), of which 365 (26.1%) were admitted to the ICU. Regarding the distribution of ABO blood groups, a significant increase in the non-O blood groups and reduction for the O blood group was observed in patients hospitalized due to COVID-19, compared to the reference general population. Among the patients admitted to the ICU, after multivariate analysis, adjusted for the rest of the confounding variables, patients with the O blood group presented a significantly lower risk for admission to the ICU. We conclude that an association was observed between patients with the O blood group and their lower susceptibility to SARS-CoV-2 infection, both for those admitted to the hospitalization ward and for those who required admission to the ICU.