A new study recently published in RMD Open investigated complement system activation and complement protein levels in relation to radiographic progression in axial spondyloarthritis (axSpA), a chronic rheumatic disease characterized by inflammation of the sacroiliac joints and spine, within a longitudinal randomized controlled trial (RCT) of radiographic axSpA patients initiating tumor necrosis factor inhibitor (TNFi) therapy.
According to the study's authors, serum samples from 96 patients with active radiographic axSpA and a high risk for radiographic spinal progression in the multicentre RCT CONSUL were analyzed by immunoassays for complement activation—C3dg and complement proteins (MBL, CL-L1, M-, H- and L-ficolin; MASP-1,–2 and −3; and MAp44) before and after 108 weeks of TNF inhibitor therapy with golimumab.
Results From the Study
The study's authors noted that baseline serum levels of total complement activation, C3dg and lectin pathway activating protease MASP-1 were elevated in patients with new bone formation (new syndesmophytes and/or growth of existing syndesmophytes) after 2 years of follow-up, whereas baseline MASP-3 levels were decreased.
The authors also explained that assessed by univariate logistic regression, baseline levels of MASP-1, MASP-3 and C3dg were associated with the development of new bone formation and remained significant in a corresponding multivariate logistic regression analysis. Also, at follow-up, they said, serum levels of C3dg and complement lectin pathway initiator L-ficolin were elevated in patients with new bone formation, and C3dg remained significant in a corresponding multivariate logistic regression analysis. Notably, the authors observed that new bone formation occurred in approximately 20% of patients despite these patients demonstrating a clinically favorable response to TNFi therapy.
Conclusions From the Study
The authors concluded that complement activation marker C3dg, MASP-1 and MASP-3 levels before TNFi therapy predicted new bone formation after 2 years of follow-up among axSpA patients with a high risk of radiographic progression. Additionally, they pointed out that levels of L-ficolin and C3dg at follow-up were elevated in axSpA patients with new bone formation. Finally, the authors said that their findings support an association between activation of the complement system and radiographic spinal progression in patients with axSpA.
Source: RMD Open
