Evaluation of the relationship between ABO and Rh blood groups and clinical course in acute pancreatitis: A retrospective observational cohort study

Early identification of patients at risk for severe acute pancreatitis (AP) remains a major clinical challenge. Although several clinical scores and inflammatory markers are used for risk stratification, their predictive performance is variable. ABO and Rh blood groups are fixed biological characteristics that have been associated with inflammatory and thrombotic conditions; however, their potential role in predicting the clinical course of acute pancreatitis remains unclear. This retrospective observational study included 512 patients hospitalized with a diagnosis of acute pancreatitis between January 2018 and May 2025. Diagnosis and disease severity were classified according to the Revised Atlanta Classification. ABO and Rh blood group information, along with demographic, laboratory, and clinical data, was obtained from the institutional hospital database. Patients were categorized as having mild or non-mild acute pancreatitis, the latter comprising moderately severe and severe disease. Statistical analyses were performed using the Chi-square test and the Mann-Whitney U test. Non-mild acute pancreatitis was observed in 17.8% of patients. The frequency of non-mild disease was significantly higher among individuals with blood group O compared with other ABO blood groups (24.5% vs 14.3%, P = .033). No significant association was identified between Rh factor and disease severity (P = .88). Male sex, obesity (body mass index ≥ 30 kg/m2), and elevated C-reactive protein levels (>150 mg/L) at admission were significantly associated with a more severe disease course. Leukocyte count, hematocrit, and peak C-reactive protein levels were higher in the non-mild group, whereas amylase and lipase levels did not differ significantly between severity categories. Blood group O was associated with a higher prevalence of non-mild acute pancreatitis in this cohort. While ABO blood group alone should not be considered a standalone prognostic marker, its integration with established clinical and inflammatory parameters may contribute to early risk stratification. Further multicenter prospective studies are warranted to clarify the role of ABO blood groups in the clinical course of acute pancreatitis.