The diagnostic value of 14-3-3η protein levels in patients with rheumatoid arthritis

14-3-3η may represent a useful diagnostic biomarker for rheumatoid arthritis (RA). We assessed the prevalence and serum levels of 14-3-3η in patients with RA and in patients with other rheumatic diseases. Serum levels of 14-3-3η were measured in 96 patients with RA, in 101 patients with other rheumatic diseases, and in 66 healthy subjects. All of the sera samples were evaluated by JOINT stat 14-3-3η ELISA test kits (Augurex Life Sciences Corp.). Median (IQR) 14-3-3η levels were significantly higher in the early RA group [0.25 ng/ml (0.075–3.11)] and in patients with established RA [0.15 ng/ml (0.08–1.26)] than in healthy subjects [0 ng/ml (0-0)] and disease controls: SLE [0.01 ng/ml (0–0.055)], AS [0.05 ng/ml (0–0.255)], and PsA [0.01 ng/ml (0–0.065)]. The prevalence of 14-3-3η positivity in patients with early RA was 58%, significantly higher than that in disease controls and healthy subjects (p < 0.001). In patients with established RA, this prevalence was 43%, and it was significantly higher than that in patients with other rheumatic diseases and healthy subjects (p < 0.05), excluding the AS group (p = 0.054). In the early RA cohort, the positivity for 14-3-3η, RF, and anti-CCP was 58%, 67%, and 71%, respectively. Eighty-two percent of the patients in this cohort were positive for at least one of these biomarkers. The concentration of 14-3-3η protein may be used to distinguish between patients with early RA and patients with other rheumatic diseases.