Novel method for measuring serum free hemoglobin in patients with hemolysis

Abstract Severe hemolysis results in excess free hemoglobin, which may cause organ damage and complicate perioperative management. Exogenous haptoglobin administration is a potential therapeutic strategy; however, its optimal use requires accurate and reliable measurement of free Hb. A novel latex agglutination immunoturbidimetric assay (LATIA) has been developed for this purpose, but its performance in clinical specimens has not been fully validated. This sub-analysis included 119 stored blood samples from 20 adult patients undergoing cardiovascular surgery. Free hemoglobin concentrations were measured using high-performance liquid chromatography (HPLC), the novel LATIA-based assay, and a conventionally used point-of-care method, with HPLC serving as the reference. Agreement between methods was assessed using Bland–Altman analysis, and perioperative changes in free hemoglobin before and after Haptoglobin administration were evaluated. Free hemoglobin levels measured by the novel assay were comparable to those obtained by HPLC, whereas the conventional method showed significant fixed and proportional biases. The novel assay demonstrated no proportional bias and minimal random error. Furthermore, changes in free hemoglobin levels following Haptoglobin administration measured by the novel assay closely reflected those measured by HPLC. These findings suggest that the novel assay provides comparable free hemoglobin measurements and may support haptoglobin dosing and perioperative management.