The Impact of ABO Blood Type on Hemoglobin Decline After Total Hip Arthroplasty

<b>Background</b>: ABO blood type was reported to have a profound influence on hemostasis. This study aimed to determine the association between ABO blood type and the hemoglobin drop after total hip arthroplasty (THA). <b>Methods</b>: We retrospectively reviewed the changes in hemoglobin after elective primary THA. Demographic characteristics were analyzed for 794 eligible THAs. Changes in hemoglobin at postoperative days 1, 7, and 14 relative to the preoperative level were analyzed for 777 THAs that did not require allogenic blood transfusion (ABT). The effects of blood type were examined using a multivariate regression model and a propensity score matching model. <b>Results</b>: The hemoglobin drop was largest at 7 days, and the values differed significantly between type O cases and non-type O cases (2.68 ± 1.08 g/dL vs. 2.41 ± 1.02 g/dL; <i>p</i> = 0.0013). In the multivariate model, blood type O was identified as an independent factor for larger hemoglobin drop at 7 days (<i>p</i> = 0.015). Lower body mass index, non-hybrid THA, higher preoperative hemoglobin level, direct lateral approach, and prophylactic use of factor Xa inhibitor were also identified as independent risk factors for larger hemoglobin drop. After successful matching of 232 THAs in type O patients with 232 THAs in non-type O patients, hemoglobin drop at 7 days was significantly larger in type O patients (-2.44 ± 1.05 g/dL vs. -2.70 ± 1.05 g/dL, <i>p</i> = 0.0092). <b>Conclusions</b>: Blood type O was independently associated with a slightly greater postoperative hemoglobin decline after primary THA; however, the absolute between-group difference was small and was not accompanied by a higher allogenic transfusion rate. Therefore, ABO blood type may represent a minor risk marker and should be interpreted in the context of clinically more relevant bleeding- and hemodilution-related factors (e.g., perioperative anticoagulant/antiplatelet therapy and underlying coagulopathies).