Serum MPO-DNA Complexes as a Biomarker of Disease Activity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by immune system dysregulation and inflammation affecting multiple organs. A key mechanism in its development involves the excessive formation and impaired clearance of neutrophil extracellular traps (NETs), which release myeloperoxidase-DNA (MPO-DNA) complexes into the circulation. Although standard laboratory markers like complement proteins (C3, C4) and anti-dsDNA antibodies are routinely used, they often show inconsistent sensitivity in monitoring disease activity and flare-ups. The primary purpose of this observational study is to evaluate serum MPO-DNA complexes as a circulating biomarker of NET formation in patients with systemic lupus erythematosus. The study aims to: * Measure serum MPO-DNA complex levels in active SLE patients compared to age- and sex-matched inactive SLE controls. * Assess the correlation between MPO-DNA complex levels and clinical disease activity measured by the SLE Disease Activity Index 2000 (SLEDAI-2K) score. * Evaluate the diagnostic accuracy of MPO-DNA complexes compared to conventional inflammatory and immunological markers (ESR, CRP, C3, C4, and anti-dsDNA). Participants will undergo routine clinical assessments and standard blood sampling to measure routine laboratory parameters and circulating MPO-DNA complex levels via enzyme-linked immunosorbent assay (ELISA).

Inclusion Criteria: * Diagnosis of systemic lupus erythematosus (SLE) according to the 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) classification criteria. * Age older than 16 years. * Provision of written informed consent prior to study enrollment. Exclusion Criteria: * Age 16 years or younger. * Overlapping autoimmune diseases (e.g., rheumatoid arthritis, systemic sclerosis, mixed connective tissue disease). * Concurrent active severe infections. * Malignancy. * Pregnancy.