14-3-3η protein in serum and synovial fluid correlates with radiographic damage and progression in a longitudinal evaluation of patients with established rheumatoid arthritis.

Objectives: The aim of the study is to examine the association between 14-3-3 eta protein levels in both serum and synovial fluid (SF) with various parameters in a longitudinal cohort of patients with established rheumatoid arthritis (RA). Methods: Serum and SF samples were obtained from RA patients and 14-3-3 eta levels were measured. Radiological damage and progression were evaluated using Sharp/van der Heijde score (SHS) at study entry and at 2-years follow-up. Results: A total of 39 RA patients were included with a mean disease duration of 9.6 +/- 8 years. Levels of 14-3-3 eta were two-fold higher in SF than in serum (mean of 3.7 versus 1.7 ng/mL, respectively). While no significant association was found between 14-3-3 eta levels with disease activity or other laboratory assessments, both serum and SF 14-3-3 eta levels positively correlated with radiographic damage at baseline (SHS; p < .001). SF, but not serum, 14-3-3 eta levels correlated with absolute progression (p < .03). Conclusion: 14-3-3 eta levels are significantly higher in RA SF than in serum in an established RA cohort. Serum and SF 14-3-3 eta levels correlate with radiographic damage at baseline and at 2-years follow-up. This study further substantiates the utility of 14-3-3 eta as a biomarker for mechanistic joint damage in established RA.