‘ROUTINE’ POSTOPERATIVE BLOODS IN ELECTIVE ARTHROPLASTY: IS IT TIME TO BREAK THE ROUTINE?

Background Routine day-one postoperative blood tests following elective arthroplasty, though not in the NICE guidelines, are common practice to detect anaemia, electrolyte imbalance and acute kidney injury (AKI). However, their universal use remains controversial in the era of enhanced recovery and cost-conscious care. Methods We retrospectively analysed 758 consecutive patients undergoing elective total hip (THR), total knee (TKR), or unicompartmental knee replacement (UKR) at a single NHS centre. Variables included ASA grade, BMI, comorbidity burden, renal disease, and anticoagulant use. The primary outcome was clinically actionable blood results (transfusion, IV fluids, electrolyte correction). Multivariate logistic regression identified independent predictors. Results Day-one blood tests were performed in 754 patients (99.5%). Only 57 (7.6%) required intervention; 92.4% showed no clinically actionable abnormality. Age ≥75 (OR 2.99, p 0.0001), ASA ≥3 (OR 3.19, p <0.0001), BMI ≥30 (OR 2.67, p 0.0020) and multiple comorbidities (OR 4.23, p <0.0001) were the strongest independent predictors. Renal disease and anticoagulant use (DOAC/warfarin) significantly increased risk. Notably, UKR patients demonstrated a particularly low intervention rate. Conclusion Routine postoperative blood testing following elective arthroplasty appears unnecessary for the majority of the patients. A risk-stratified strategy — targeting Age ≥75, ASA grade ≥3, comorbidities ≥3, renal impairment, high BMI, and anticoagulated patients — could safely reduce unnecessary investigations, improve resource utilisation, lower costs and improve patient experience. These findings support development of a clinical risk tool to guide selective postoperative testing. Prospective validation is warranted.