Circulating Neutrophil Extracellular Traps as Disease Severity Markers for Rheumatoid Arthritis: A Case-control Study

Background: Neutrophil extracellular traps (NETs) have emerged as potential biomarkers in autoimmune diseases. This study aimed to evaluate NETs as markers of disease severity in rheumatoid arthritis (RA). Methods: A prospective cross-sectional study was conducted from May 2022 to December 2023 at a tertiary care hospital in Western India. Patients with RA were categorised into high disease activity (HDA-RA) and low disease activity (LDA-RA) groups based on the DAS-28-CRP score (≥3.2 vs <3.2). Age and sex-matched healthy individuals served as the control group. Levels of NETs markers, cell-free DNA (cfDNA), myeloperoxidase-DNA (MPO-DNA) complexes and citrullinated histone-3 (citH3), along with conventional markers (C-reactive protein [CRP] and erythrocyte sedimentation rate [ESR]) were measured and compared across groups. Results: Patients with HDA-RA demonstrated significantly elevated levels of NET markers—cfDNA (197.7 ± 18.7 ng/mL), MPO-DNA (67.3 ± 12.0 mAU/mL) and citH3 (4.1 ± 1.4 ng/mL)—compared to low disease activity (LDA-RA) and controls ( P < .001). NET markers correlated strongly with CRP, ESR and DAS-28-CRP ( r = 0.436–0.647, P < .001). Logistic regression confirmed cfDNA, MPO-DNA and citH3 as the independent predictors of RA disease severity, with citH3 showing the strongest association (odds ratio = 2.871, 95% confidence interval: 1.786–4.616, P < .001). Receiver operating characteristic analysis identified cfDNA as the most accurate marker for distinguishing HDA-RA from LDA-RA (area under the curve = 0.87, sensitivity 81%, specificity 79%), outperforming traditional markers. Conclusions: NET markers, especially cfDNA, may complement traditional inflammatory markers in assessing RA disease severity. While their diagnostic advantage appears modest, further research is warranted to explore their broader utility in RA management.