Abstract
Blood groups significantly influence individuals' immune responses and the severity of diseases. This study examined the association between ABO blood groups and clinical features, comorbidities, and outcomes in COVID-19 patients in southeast Iran. This retrospective cross-sectional study included 894 RT-PCR-confirmed COVID-19 patients admitted to two referral hospitals in southeast Iran (April-September 2020). Medical records were reviewed for demographic data, ABO blood groups, clinical features, comorbidities, and outcomes. Disease severity was classified using NIH criteria. Chi-square, Kruskal-Wallis, and multivariable logistic regression (adjusted for age, sex, and comorbidities) were used for analysis. The mean age was 37.36 ± 14.63 years, and 53.1% were female. The mean number of symptoms varied significantly across ABO blood groups (P = 0.014), with group AB showing the lowest values. Hospitalization rates also differed (P = 0.003), being highest in group O. Significant associations were observed between blood groups and fever/chills, cough, rhinorrhea, headache, and gastrointestinal symptoms (all P < 0.05). Comorbidities were more frequent in group O (P = 0.005), particularly cardiovascular disease (P = 0.037). Blood group AB remained independently associated with fewer symptoms after adjustment (aOR = 0.68, 95% CI 0.47-0.98). ABO blood groups were associated with clinical presentation and comorbidities in COVID-19 patients. Blood group O showed higher rates of comorbidities and hospitalization, while blood group AB had a milder symptom profile.