Serum 14-3-3η is a novel joint-derived proinflammatory mediator associated with rheumatoid arthritis (RA). This study aimed to evaluate the diagnostic capacity of serum 14-3-3η and its correlation with clinical variables in patients with RA.

A total of 94 patients with RA and 80 age- and sex-matched controls, including 40 healthy subjects, were included. Serum 14-3-3η levels were assessed by quantitative enzyme-linked immunosorbent assay. Receiver-operating characteristic (ROC) curves analysis was used to determine the sensitivity and specificity of 14-3-3η. Spearman's rank correlation coefficient was used to assess the relationship between 14-3-3η and other clinical measures in patients with RA.

Median (interquartile range) of serum 14-3-3η concentration (ng/ml) in RA patients (2.34 [1.56-3.39]) was significantly higher than that in healthy subjects (0.17[0.11-0.30]) and disease controls (1.66[1.21-2.74]; <0.05). ROC curve analysis comparing patients with RA with all controls demonstrated a significant (<0.001) area under the curve (AUC) of 0.81 (95% confidence interval: 0.74-0.88). At a cutoff of 1.44 ng/mL, the ROC curve yielded a sensitivity of 78.7% and specificity of 73.8%. The sensitivity of anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF) were 84.0% and 72.3%, respectively. Adding 14-3-3η to ACPA and/or RF discriminated more than 96% of patients with RA. The positive rate of at least one of the three markers was up to 99%, with a specificity of about 70%. The results of correlation analyses revealed that serum levels of 14-3-3η protein positively correlated with C-reactive protein (r=0.250, <0.05), erythrocyte sedimentation rate (r=0.294, <0.01), and 28-joint disease activity score (r=0.275, <0.05) in patients with RA.

14-3-3η protein is a novel marker that can apparently enhance the detection rate of patients with RA. The level of serum 14-3-3η protein correlates to some degree with disease activity.