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Objectives and questions: The necessity of routine postoperative laboratory testing in patients undergoing total hip arthroplasty (THA) has recently been questioned. To reduce unnecessary blood tests while still effectively identifying patients requiring transfusion—and thus targeting those who may benefit from postoperative blood tests—two risk scoring systems have been developed and recently published. This study aims to evaluate, compare, and validate these scoring systems in an unselected cohort of patients undergoing primary THA.

Material and methods: We conducted a retrospective study of patients who underwent THA for primary indications between 2021 and 2024 at an academic institution. Patients undergoing revision surgery, those with a history of hip surgery, and those with oncologic indications were excluded. Patient demographics, clinical information, and laboratory test results were collected from electronic medical records. Two risk scoring systems—the Total Hip Arthroplasty Blood Test Usefulness Score (THABUS) and Wu et al.’s score—were calculated for each patient.

As these scoring systems are designed to identify patients who may benefit from a postoperative blood test while reducing unnecessary routine laboratory testing, we excluded 21 patients with intraoperative blood loss exceeding 1,200 mL, as they automatically received postoperative blood tests due to significant hemorrhage. Additionally, eight patients with intraoperative complications were excluded, three of whom required transfusions. After applying these exclusion criteria, 346 patients remained for analysis.

Results: The transfusion rate was 3.46% (10/346). The THABUS formula determined that postoperative blood tests were unnecessary in 246 patients and necessary in 100 patients. One patient (1/10, 10%) was a false negative, resulting in a sensitivity of 90% and specificity of 72.3%, respectively. Wu et al.’s risk scoring system identified 124 patients as needing a postoperative blood test. However, 5 patients (5/10, 50%) who required a transfusion were missed by the risk scoring system, resulting in a predicted risk of transfusion with a sensitivity of 50% and a specificity of 64.5%.

Discussion and conclusions: This study validates the THABUS formula as a sensitive and specific tool for identifying patients who require postoperative blood tests while reducing unnecessary laboratory exams. By optimizing test utilization, the THABUS formula proves to be cost-efficient while maintaining patient safety. These findings support the notion that routine, systematic postoperative laboratory testing after THA is unnecessary in modern clinical practice. Risk-scoring systems can aid in clinical decision-making by guiding when laboratory tests should be performed following THA.