Abstract
Introduction: Evidence from basic and clinical studies supports the role of complement activation in myelin oligodendrocyte glycoprotein antibody-related disease (MOGAD). However, the complexity of complement components hinders its clinical application. Objectives/Aims: This study aims to explore the potential of clinical practical serum complement indicators as biomarkers for MOGAD disease activity. Methods: We retrospectively included 171 records of commonly used serum complement indicators, immunoglobulin, and systemic inflammatory markers from 96 MOGAD patients and 185 records from 97 NMOSD cases. Results: MOGAD patients exhibited higher C3 (acute phase, p = 0.027; whole course, p = 0.003), C4 (acute phase, p < 0.001; whole course, p < 0.001), and CH50 (acute phase, p = 0.021) levels than NMOSD patients. In the MOGAD cohort, elevated CH50 levels were found in 76.47% (130/170) cases, with higher frequencies during the acute phase at 80.82% (59/73). In the acute phase, MOGAD patients showed increased C4 (p = 0.022), CH50 (p = 0.021), and IgG (p = 0.031) levels. We also observed the dynamic fluctuations in complement concentrations after clinical attacks in MOGAD, with complement concentrations peaking during the acute phase and declining during remission (C3, 81.82%, 9/11; C4, 63.64%, 7/11; CH50, 72.73%, 8/11). A positive correlation was noticed between CH50 and IgG (r = 0.317, p = 0.006). Complement levels related positively with CRP (C3, r = 0.316, p = 0.006; C4, r = 0.303, p = 0.009; CH50, r = 0.230, p = 0.050) and ESR (C3, r = 0.537, p < 0.001; C4, r = 0.280, p = 0.043; CH50, r = 0.478, p < 0.001). C4 levels were positively associated with CSF white cell count (r = 0.217, p = 0.030). Patients with higher CH50 levels tended to experience earlier recurrence than those with lower CH50 levels (log-rank p = 0.076). Conclusion: Clinically practical complement indicators can reflect disease activity, and CH50 can serve as candidate prognostic biomarkers for relapse in MOGAD.