[Significance of the 50% hemolytic complement in hemolysis assessment and efficacy of eculizumab in patients with paroxysmal nocturnal hemoglobinuria].

This study retrospectively analyzed data from 25 patients with paroxysmal nocturnal hemoglobinuria (PNH) admitted to Peking Union Medical College Hospital and Dongfang Hospital of Beijing University of Chinese Medicine from January 2023 to June 2024. Patients receiving sufficient eculizumab treatment for at least 3 months and who completed hemolytic complex (CH50) level testing pre- and post-treatment for 3 and 6 months were selected. Blood routine, biochemistry, and the 50% CH50-related indicators were monitored pre- and post-treatment. Among these patients, 24 completed 6 months of treatment and CH50 testing. After 3 and 6 months of eculizumab treatment, all patients with PNH showed significant improvement in symptoms, with lactate dehydrogenase (LDH) levels decreasing from a baseline of (1 814.4 ± 924.8) U/L to (248.5 ± 61.0) U/L and (239.3 ± 44.8) U/L. Hemoglobin levels increased from a baseline of (73.9±14.4) g/L to (99.9 ± 21.3) g/L and (99.6 ± 19.8) g/L. The baseline CH50 level was (32.4±14.7) %, which decreased to 2.0% (1.0% -8.0% ) and 1.0% (1.0% -4.0% ) at 3 and 6 months posttreatment, respectively. At baseline, a linear correlation was found between CH50 and LDH levels (P<0.001), and the trend of CH50 changes was significantly lower than LDH at 3 and 6 months post-treatment with eculizumab, with similar trends. However, no linear correlation was observed between CH50 and LDH levels or other parameters at 3 and 6 months of medication. Our case demonstrates that eculizumab is effective for PNH hemolysis treatment. The serum CH50 level may be a biomarker for complement blockade induced by eculizumab, which can, to some extent, reflect the intravascular hemolysis of PNH and the efficacy of eculizumab.