Soluble urokinase plasminogen activator receptor (suPAR) in the assessment of inflammatory activity of rheumatoid arthritis patients in remission

Abstract

Soluble urokinase plasminogen activator receptor (suPAR) is a biomarker increasingly used for the assessment of systemic inflammation. We aimed to evaluate suPAR for the assessment of inflammatory activity in rheumatoid arthritis (RA) patients in remission. In our cross-sectional study we measured plasma suPAR and C-reactive protein (CRP) levels as well as erythrocyte sedimentation rate (ESR) in 120 RA patients at various stages of disease activity and 29 healthy age-matched controls. suPAR, CRP and ESR values were higher in RA patients compared to healthy individuals. When suPAR levels were analyzed according to DAS28 scores of RA patients, suPAR level in the subgroup with DAS28≤2.6 was lower than in the subgroup with DAS28>2.6, but still higher than in controls [4.45 (3.33-5.56) ng/mL vs. 3.66 (3.10-4.67) ng/mL vs. 2.80 (2.06-3.42) ng/mL, p<0.0001, median (interquartile range)]. In contrast, CRP and ESR values were comparable in the subgroup with DAS28≤2.6 and in healthy individuals. We further analyzed the correlation between the number of tender and/or swollen joints and suPAR levels in RA patients in remission. suPAR values were significantly higher in patients with four tender and/or swollen joints than in patients with 2-3 or 0-1 tender and/or swollen joints. While CRP and ESR values indicate remission of the chronic inflammatory process in RA, suPAR values are still elevated compared to healthy individuals. suPAR might be particularly valuable in the recognition of inflammatory activity in patients who are in remission according to DAS28 scores but have symptoms of tender and/or swollen joints.