Prevalence of ABO Blood Groups and Their Relationship with Vascular Access Thrombosis and Mortality in Hemodialysis Patients

Background and Objectives: ABO and Rh blood group systems represent clinically relevant genetic polymorphisms with established associations beyond transfusion medicine, including thrombotic risk. We investigated the prevalence of ABO and Rh blood group phenotypes in hemodialysis patients and their associations with documented vascular access thrombosis and all-cause mortality. Materials and Methods: This retrospective cohort study analyzed 3027 patients receiving maintenance hemodialysis in Hatay province, Türkiye, between January 2010 and April 2025. Data included ABO and Rh blood group determination, demographics, comorbidities, dialysis vintage, vascular access type, vascular access thrombosis events, and mortality. Multivariable binary logistic regression was used to identify independent factors associated with documented vascular access thrombosis. Multivariable Cox proportional hazards regression with vascular access thrombosis modeled as a time-dependent covariate was used to identify independent predictors of all-cause mortality. Results: Mean patient age was 63.95 ± 13.74 years; 58.3% were men. Blood group A was most prevalent (41.4%), followed by O (35.8%), B (15.9%), and AB (6.9%); 92.7% were Rh-positive. Documented vascular access thrombosis differed significantly by ABO group (p = 0.027), with the highest rate in group A (14.1%). In multivariable logistic regression, non-O blood group (OR 1.34, 95% CI 1.06–1.70; p = 0.014) and longer dialysis vintage (OR 1.01 per month, 95% CI 1.00–1.01; p < 0.001) were independently associated with documented vascular access thrombosis. In multivariable Cox regression, time-dependent vascular access thrombosis was independently associated with higher all-cause mortality (HR 1.33, 95% CI 1.12–1.59; p = 0.002), as were age (HR 1.02; p < 0.001), diabetes mellitus (HR 1.49; p < 0.001), coronary artery disease (HR 1.34; p < 0.001), and hypertension (HR 1.19; p < 0.001). Arteriovenous fistula was associated with lower mortality compared with temporary catheter (HR 0.46, 95% CI 0.37–0.58; p < 0.001). Blood group phenotype was not independently associated with all-cause mortality (all p > 0.5 vs. group O). Conclusions: In hemodialysis patients, non-O blood groups were modestly but independently associated with documented vascular access thrombosis, and vascular access thrombosis was independently associated with increased mortality when modeled as a time-dependent exposure. Blood group phenotype was not independently associated with mortality after adjustment for established risk factors. Blood group may contribute incrementally to vascular access risk awareness alongside established clinical risk factors, but its modest absolute risk difference limits standalone clinical utility.