Mortality and outcomes by blood group in trauma patients: A systematic review and meta-analysis

Background and Objectives: Blood group O contains lower levels of factor VIII and von Willebrand factor. Higher incidence of bleeding among group O is reported in multiple contexts. Results of studies vary regarding outcomes stratified by blood group in trauma. We systematically reviewed the literature for outcomes related to blood group in trauma patients. Meta-analysis of studies evaluating mortality related to blood group was performed.Materials and Methods: The PubMed and Embase databases were searched for studies analysing relationships between blood group and outcomes in trauma patients. Preferred Reporting Items in Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. We synthesized outcomes data related to blood group. Meta-analysis compared mortality rates between group O and non-O patients.Results: Inclusion criteria were met by 13 studies. Statistically significant differences by blood group were reported in 3 of 10 (30%) studies evaluating mortality, 2 of 3 (66.7%) evaluating mortality from haemorrhage and 2 of 9 (22.2%) evaluating transfusion requirement. Meta-analysis was performed on seven studies evaluating mortality (total n = 11,835). There was significant heterogeneity among studies (I-2 = 86%, p < 0.00001). No difference was found in mortality between group O and non-O patients (relative risk = 1.21, 95% confidence interval = 0.89-1.64, p = 0.23).Conclusion: Existing literature does not consistently demonstrate a mortality difference between trauma patients with O and non-O blood groups. High variability in the methods and results among studies limits this conclusion, and further research is needed to delineate under what circumstances blood group may influence outcomes.