Serum sodium/potassium ratio in patients with rheumatoid arthritis and osteoarthritis

Rheumatoid arthritis (RA) and osteoarthritis (OA) may cause rapid joint destruction and chronic disability. The main pathological feature of RA is chronic synovitis, resulting in bone resorption due to TNF-a-RANKL-DKK-1 mechanism. The main pathological feature of OA is increased osteophyte formation governed by members of the TGF/BMP protein family, as well as by the group of Wingless (Wnt) proteins. The renin-angiotensin-adosterone system has been identified as an important regulator of fibrosis and is being investigated as a potential target for antifibrotic drugs. Experimental evidence also indicates that aldosterone directly contributes to accelerate damage by sustaining cell growth, inflammation and fibrosis reactions. This occurs through production of growth factors including TGF-b. The objective of this study was to investigate serum sodium/potassium ratio (SSPR) as an indicator of aldosterone function in patients with OA and RA. Retrospective analysis of SSPR of patients aged 40-70 with active RA (n=50 patients) and OA (n=30) was performed as of medical records from the in-patient clinic. These findings were compared with the data of SSPR of healthy controls (n=30). SSPR of patients with RA, OA and healthy controls was within the recognized normal range (27-40). The lowest SSPR was found in healthy controls: 30.9±2.4. Significantly higher values were found in the RA group (32.9±2.9; P less then 0.001) and OA patients (34.3±2.1; P less then 0.001). The SSPR was significantly higher in the OA group compared to RA (P=0.004). No correlation was observed between SSPR and age (P=0.534). We conclude that patients with OA had relatively increased SSPR, indirectly indicating increased aldosterone function compared with controls and patients with RA.