Objective Systemic lupus erythematosus (SLE) is a clinically heterogeneous disease with limited reliable diagnostic biomarkers. We investigated whether gene methylation could meet sensitivity and specificity criteria for a robust biomarker. Methods IFI44L promoter methylation was examined using DNA samples from a discovery set including 377 patients with SLE, 358 healthy controls (HCs) and 353 patients with rheumatoid arthritis (RA). Two independent sets including 1144 patients with SLE, 1350 HCs, 429 patients with RA and 199 patients with primary Sjögren’s syndrome (pSS) were used for validation. Results Significant hypomethylation of two CpG sites within IFI44L promoter, Site1 (Chr1: 79 085 222) and Site2 (Chr1: 79 085 250; cg06872964), was identified in patients with SLE compared with HCs, patients with RA and patients with pSS. In a comparison between patients with SLE and HCs included in the first validation cohort, Site1 methylation had a sensitivity of 93.6% and a specificity of 96.8% at a cut-off methylation level of 75.5% and Site2 methylation had a sensitivity of 94.1% and a specificity of 98.2% at a cut-off methylation level of 25.5%. The IFI44L promoter methylation marker was also validated in an European-derived cohort. In addition, the methylation levels of Site1 and Site2 within IFI44L promoter were significantly lower in patients with SLE with renal damage than those without renal damage. Patients with SLE showed significantly increased methylation levels of Site1 and Site2 during remission compared with active stage. Conclusions The methylation level of IFI44L promoter can distinguish patients with SLE from healthy persons and other autoimmune diseases, and is a highly sensitive and specific diagnostic marker for SLE.

doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.

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Objectives: To describe a prospective cohort of patients with rheumatoid arthritis associated with interstitial lung disease (RA-ILD) and identify risk factors associated with disease progression and mortality in this cohort. Patients and methods: We performed a multicenter, prospective, observational study of patients with RA-ILD receiving disease-modifying antirheumatic drugs (DMARDs) between 2015 and 2020. The patients were assessed using high-resolution computed tomography and pulmonary function tests at baseline and at 60 months. The main endpoint was “Progression to ILD at the end of follow-up” in terms of the following outcomes: (1) improvement (i.e., improvement in forced vital capacity (FVC) ≥ 10% or diffusing capacity of the lungs for carbon monoxide (DLCO) ≥ 15% and absence of radiological progression); (2) nonprogression (stabilization or improvement in FVC ≤ 10% or diffusing capacity of the lungs for carbon monoxide (DLCO) < 15% and absence of radiological progression); (3) progression (worsening of FVC > 10% or DLCO > 15% and radiological progression); or (4) death. We recorded demographic and clinical characteristics, lung function, and the incidence of adverse events. A Cox regression analysis was performed to identify factors associated with the worsening of ILD. Results: After 60 months, lung disease had stabilized in 66 patients (56.9%), improved in 9 (7.8%), and worsened in 23 (19.8%). Eighteen patients (15.5%) died, with a mean survival of 71.8 (1.9) months after diagnosis of ILD. The Cox multivariate analysis revealed the independent predictors of worsening of RA-ILD to be usual interstitial pneumonia (hazard ratio (HR), 2.6 (95%CI, 1.0–6.7)), FVC <80% (HR, 3.8 (95%CI, 1.5–6.7)), anticitrullinated protein antibody titers (HR, 2.8 (95%CI, 1.1–6.8)), smoking (HR, 2.5 (95%CI, 1.1–6.2)), and treatment with abatacept, tocilizumab, or rituximab (HR, 0.4 (95%CI, 0.2–0.8)). During follow-up, 79 patients (68%) experienced an adverse event, mostly infection (61%). Infection was fatal in 10/18 patients (55.5%) during follow-up. Conclusions: Lung function is stable in most patients with RA-ILD receiving treatment with disease-modifying anti-rheumatic drugs (DMARDs), although one-third worsened or died. Identifying factors associated with worsening in RA-ILD is important for clinical management.