Clinical algorithm model based on cfDNA to predict SLE disease activity

Background Circulating cell-free DNA (cfDNA) has been widely used as a new liquid-biopsy marker. Dysregulation of cfDNA has been found in patients with systemic lupus erythematosus (SLE). However, the detailed association between cfDNA and SLE has not been thoroughly studied. Methods Plasma samples were collected from 88 patients with active SLE and 39 patients with inactive SLE. The cfDNA concentration was determined, and the length and distribution of cfDNA fragments were verified. Results cfDNA concentrations were significantly higher in patients with active SLE than in patients with inactive SLE (0.4 [0.18–0.897] ng/µL vs 0.249 [0.144–0.431] ng/µL; p = .043). cfDNA fragments were enriched in the ranges of 153–198 bp and 300–599 bp. cfDNA concentrations were associated with the reduction of the anti-double-stranded DNA (dsDNA) antibodies titer (r = −0.301, p = .034). The presence of anti-U1 ribonucleoprotein ( p = .012), anti-Sjogren syndrome A ( p = .024), anti-dsDNA ( p = .0208), and anti-nucleosome antibodies ( p = .0382) might associate to the variation of cfDNA concentration. Reduced cfDNA concentration was associated with renal damage in active SLE patients (0.31 [0.11–0.73] ng/µL vs 0.65 [0.27–1.53] ng/µL; p = .009). The Active index, a combination model including cfDNA concentration and other clinical indices, had an area of 0.886 under the receiver operating characteristics curve for distinguishing active SLE. The Active index was positively correlated with the SLE disease activity index score (r = 0.6724, p < .0001). Conclusions Through systematic stratified analysis and clinical algorithm model, this study found that plasma cfDNA concentration is closely related to SLE disease severity, which has guiding significance for the future clinical application of cfDNA in SLE.