Perioperative Factors Associated With Allogeneic Blood Transfusion in Elective THA

ABSTRACT Background Identifying predictors of perioperative blood transfusion is essential for optimizing patient safety and perioperative blood management in total hip arthroplasty (THA). This Study aimed to identify perioperative factors independently associated with transfusion. Methods This retrospective study included all elective primary THA procedures performed between 2016 and 2023 at a certified Endoprosthetic Center. Demographic, clinical, laboratory, and operative variables were extracted. Total and hidden blood loss were calculated using the Nadler and Gross/Sehat formulas. A multivariable logistic regression model was fitted to identify independent factors associated with transfusion. Receiver operating characteristic (ROC) analyzes were performed for cup inclination and the 48‐h hematocrit. Cutoff thresholds were derived using Youden's index, and combined decision rules (AND/OR) were evaluated. Results Among 39 predictors, three variables were independently associated with transfusion: cup inclination (OR = 0.89; p = 0.0003), 48‐h hematocrit (OR ≈5.17 × 10 −48 ; p = 0.023), reflecting quasi‐separation due to a near‐deterministic threshold effect rather than a literal effect size, and reoperation (OR = 13.19; p = 0.049). The model demonstrated excellent discrimination (AUC = 0.931). Inclination alone showed negligible predictive value (AUC = 0.393). The 48‐h hematocrit was a strong single predictor (AUC = 0.817) with a clinically meaningful threshold (< 0.28 L/L). Combined rules showed moderate performance; the OR rule was ineffective. Conclusion Early postoperative hematocrit is a robust and clinically actionable marker associated with transfusion risk in primary THA. Cup inclination reflects the surgical technique rather than direct transfusion risk, and reoperation likely indicates underlying perioperative complexity. Transfusion strategies should prioritize hematocrit‐based evaluation rather than inclination‐based thresholds. Level of Evidence III—retrospective single‐center observational cohort study.