Soluble receptor for advanced glycation end products (sRAGE) in plasma and synovial fluid is inversely associated with disease severity of knee osteoarthritis

Objectives:The aim of this study was to measure soluble receptor for advanced glycation end products (sRAGE) in plasma and synovial fluid of knee osteoarthritis (OA) patients and to determine the correlation between sRAGE levels and disease severity.Design and methods:Thirty-six OA patients and 15 healthy controls were enrolled in this study. OA grading was performed using the Kellgren–Lawrence classification. sRAGE levels in plasma and synovial fluid were analyzed by enzyme-linked immunosorbent assay.Results:Plasma sRAGE levels were significantly lower in OA patients than in healthy controls (P = 0.01). sRAGE levels in plasma were remarkably higher with regard to paired synovial fluid (P = 0.001). Additionally, sRAGE concentrations in plasma and synovial fluid showed significant inverse correlation with disease severity (r = −0.65, P < 0.001 and r = −0.55, P = 0.001, respectively). Further analysis showed that there was a strong positive correlation between plasma and synovial sRAGE concentration (r = 0.81, P < 0.001).Conclusions:sRAGE levels were significantly lower in OA patients compared with controls, and sRAGE levels in plasma and synovial fluid also decreased significantly as the disease severity increased. Accordingly, sRAGE levels could be used as a biochemical marker for assessing the severity and progression of knee OA.