Evaluation of Serum Protein 14-3-3η (Eta) as a Novel Biomarker for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common systemic autoimmune diseases. New markers are needed for early diagnosis of RA as seronegativity in both early and established RA remains a major limitation of both anticitrullinated protein antibodies (ACPA) and rheumatoid factor (RF). The 14-3-3η protein may represent a novel biomarker for the detection of RA. We evaluated the diagnostic performance of serum 14-3-3η protein in early and established cases of rheumatoid arthritis and we compared the diagnostic accuracy of it with those of the well-known RA markers (e.g. RF and ACPA). Sera from 50 patients with RA (20 early and 30 established) based on the 2010 ACR / EULAR Rheumatoid Arthritis Classification Criteria, 15 patients with non-RA arthritis as diseases control group (8 patients with OA and 7 patients with SLE) and 14 healthy controls were enrolled in the study. Serum RF was determined by latex, ACPA and 14-3-3η protein were determined by ELISA. Serum 14-3-3η protein levels in patients with RA were significantly higher (P=0.001*) as compared to healthy individuals. For serum 14-3-3η diagnostic accuracy in RA; Receiver operating characteristic curves (ROC) analysis comparing patient with RA with healthy control showed AUC (0.916) at optimum cutoff of > 2.5ng/mL, and a sensitivity of 100%, a specificity of 78.57%, a PPV of 94.3, and an NPV of 100. No significant difference in 14-3-3η protein serum levels was found between early and established RA groups. It was positive in 100% of early and established RA patients who were seronegative for RF and ACPA. It is concluded that, 14-3-3η protein could improve the sensitivity of RA diagnosis and cover the shortage of detection of RF and ACPA in RA patients.