[Correlation between complement deposition levels on blood cells and clinical biomarkers in patients with paroxysmal nocturnal hemoglobinuria].

<b>Objective:</b> To explore the complement deposition levels on blood cell surfaces in patients with paroxysmal nocturnal hemoglobinuria (PNH) and evaluate their association with clinical manifestations. <b>Methods:</b> This study enrolled patients with PNH, who had not been treated with complement inhibitors and appeared at Peking Union Medical College Hospital from February 2021 to February 2023. The clinical information of participants was retrospectively recorded, and peripheral blood samples were collected. Gender- and age-matched normal controls (NC) were recruited accordingly. C5b-9, C3, C4b, and factor B (FB) deposition levels on peripheral red blood cells, white blood cells, and platelets were detected with flow cytometry. The correlation between complement deposition levels and clinical symptoms was analyzed. <b>Results:</b> This study involved 73 patients with PNH, including 42 (57.5%) males, with a median age of 36 (range: 14-76) years. 16 matched NC were collected. Among patients with PNH, 36 (49.3%) had classical PNH and 37 (50.7%) had aplastic anemia-PNH syndrome. Thromboembolic events (TEE) occurred in 18 (24.7%) patients. The median HGB, absolute reticulocyte count (Ret), and lactate dehydrogenase of PNH patients were 76 (37-116) g/L, 181.0 (45.9-495.8) ×10(9)/L, and 1 875 (377 - 5 509) U/L, respectively. The median number of Flaer-negative white blood cells was 94.0% (13.0% - 99.9%) ; the median CD59 negative red blood cells was 46.7% (9.0% - 93.0%). The deposition of C5b-9, C3, C4b, and FB on red blood cells, white blood cells, and platelets in patients with PNH was significantly higher than that in NC (all <i>P</i><0.05). C5b-9 deposition level was significantly higher than that of C3, C4b, and FB on all three blood cell lineages in PNH patients (all <i>P</i><0.01). The deposition of all complement fragments on red blood cells was significantly lower than that on white blood cells and platelets (all <i>P</i><0.01). C5b-9 deposition on red blood cells was positively correlated with Ret in PNH patients (<i>P</i>=0.005). C3 (<i>P</i>=0.001) and C4b (<i>P</i>=0.017) deposition levels on white blood cells and C3 deposition on platelets (<i>P</i>=0.002) in patients with TEE history were lower than those without. <b>Conclusions:</b> C5b-9, C3, C4b, and FB deposition levels on all three blood cells in patients with PNH were higher than NC. Increased C5b-9 on red blood cells may indicate active hemolysis. Reduced C3 and C4b levels on white blood cells and low C3 deposition on platelets may indicate TEE risk.