Alternatively spliced EDA-containing fibronectin in synovial fluid as a predictor of rheumatoid joint destruction

Objectives. Fibronectin containing the EDA region (EDA (+) Fn), a molecule important for rheumatoid joint destruction, was measured in relation to the progression of joint destruction in rheumatoid arthritis (RA). Methods. Total Fn and EDA (+) Fn were measured by ELISA, and the concentrations of Fn in plasma and synovial fluid were compared prospectively for 2 yr with the progression of joint destruction in 41 knee joints of 37 patients with RA. The extent of joint destruction was assessed by the Larsen score and joint space narrowing in X-ray films taken before and 2 yr after measurement of EDA (+) Fn. Results. The concentration of synovial fluid EDA (+) Fn showed a positive correlation with the progression of joint destruction in RA (r = 0.78). While total Fn in synovial fluid also showed a correlation with joint destruction (r = 0.54), total Fn and EDA (+) Fn in plasma showed no correlation with joint destruction. The concentration of synovial fluid EDA (+) Fn was significantly higher in patients who underwent joint replacement after the measurement of EDA-Fn than in those who did not receive surgery (P < 0.029). Conclusion. Synovial fluid EDA (+) Fn can be a predictor of subsequent joint destruction in RA.