Accuracy and agreement of three blood-loss estimation methods versus the HbMass method for assessing blood loss during PLIF.

Abstract

To evaluate the accuracy and agreement of three widely used blood-loss estimation methods-visual estimation, gravimetric measurement, and the Gross formula method-against the reference HbMass method in patients undergoing posterior lumbar interbody fusion (PLIF). A single-center retrospective cohort study included 1000 consecutive elective PLIF patients (2021-2024). Intra-operative blood loss was quantified intra-procedurally by visual, gravimetric, and Gross formula method approaches; HbMass was calculated from pre- and post-operative hemoglobin with patient blood volume estimated by the Nadler equation. Agreement was assessed with Bland-Altman 95% limits of agreement (LoA) and Spearman correlation; sensitivity analyses examined fusion extent, irrigation volume, and sampling timing. Mean blood loss was 663.8 ± 155.6 mL by HbMass. Visual, gravimetric, and Gross estimates averaged 456.5 ± 175.0 mL, 599.8 ± 167.5 mL, and 608.0 ± 115.0 mL, respectively (all P < 0.001). Correlation with HbMass was negligible (ρ = 0.185), weak (ρ = 0.424), and moderate-to-strong (ρ = 0.742). Bland-Altman biases (95% LoA) were - 238.85 mL (- 631.46, 153.76), - 45.33 mL (- 377.55, 286.90), and - 28.57 mL (- 216.66, 159.52). Sensitivity analyses confirmed robustness. Among routine methods, the Gross formula method offers the smallest bias and narrowest agreement limits versus HbMass, whereas visual estimation is clinically unreliable. PLIF-enhanced recovery pathways should replace sole reliance on visual assessment with the Gross formula method, supplemented by HbMass in high-risk cases, to optimize peri-operative volume therapy and reduce transfusion-related complications.