Utility of sUPAR as a Novel Biomarker for Stratifying Rheumatoid Arthritis Patients in Remission

Abstract

Introduction: Soluble urokinase plasminogen activator receptor (SuPAR) is a novel biomarker studied in conditions such as infections and malignancies. There is a paucity of data on suPAR levels in patients in RA clinical remission. A hypothesis-driven study was conducted to determine the level of suPAR, which will aid in the stratification of patients in remission. Methodology: This observational pilot study included 48 subjects (24 rheumatoid arthritis [RA] patients in clinical remission as per the American College of Rheumatology criteria and 24 age-matched healthy individuals). 28-Joint Disease Activity Score (DAS28) calculator was used to calculate disease activity. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and plasma suPAR levels were assessed using suPARnostic® ELISA Assay kit (ViroGates, Denmark). The inflammatory parameters such as CRP, ESR, and suPAR were recorded at the time the patients were defined to be in clinical remission. Results: The median of suPAR level among cases in remission was 4.94 ng/mL and in controls was 3.54 ng/mL. The level of serum suPAR among RA remission patients was significantly higher (P < 0.001) than in healthy individuals (P < 0.001). The median of DAS28 score was 2.10, ESR 23, and CRP was 2.66. Nonparametric analysis (Spearman’s rho test) showed a significant correlation (P = 0.008) between DAS28 and ESR. The receiver operating characteristic showed area under the curve of 0.954 with sensitivity 83.3%, specificity 100%, negative predictive value 84%, and positive predictive value 100%. Conclusion: High suPAR levels among patients with clinical remission of RA demonstrate that these patients do possess baseline inflammatory status and hence continued treatment is required despite normal to mild range of ESR, CRP, and/or DAS 28 score. Thus, suPAR is a prognostic biomarker that can aid in better therapeutic management to patients with RA remission.