Evaluation of 14-3-3eta protein as a diagnostic biomarker in the initial assessment of inflammatory arthritis

Serum 14-3-3eta are novel biomarkers of rheumatoid arthritis (RA). It is not clear whether 14-3-3eta may be present in other forms of inflammatory arthritis (IA). We evaluated the presence of 14-3-3eta as a diagnostic biomarker in the evaluation IA. A retrospective cohort study of adult patients who were evaluated for IA by a rheumatologist with a result for the lab test of 14-3-3eta was conducted. Of 280 included patients, 30% were diagnosed with RA, 11% with psoriatic arthritis (PsA), and 59% with another condition. Twenty-four (9%) patients had positive results for 14-3-3eta. Fifty-two percent of positive patients were diagnosed with RA, with 48% having another diagnosis including axial spondyloarthritis, gout, Sjögren's, undifferentiated IA, diabetic cheiroarthropathy, prostate cancer with bone metastasis, osteoarthritis, unspecified arthralgia. No patients with PsA had a positive value. RA patients had a higher value for 14-3-3eta compared to non-RA (5.44 [1.56~9.31] vs. 0.69 [0.40~0.98] ng/mL, p=0.03, square brackets are 95% confidence interval values). The mean value for the 14-3-3eta in seropositive RA trended higher than seronegative (8.0 [2.3~13.7] vs. 1.4 [0.4~2.4] ng/mL, p=0.06). In the RA cohort, elevated 14-3-3eta was associated with elevated erythrocyte sedimentation rate (odd ratio=6.62 [1.24~47.09], p<0.04), but not other variables. 14-3-3eta may aid as a diagnostic biomarker of RA. However, it is not specific for RA, especially at low positive levels, and may be positive in other forms of IA. Ideal cutoff values need to be established for RA and non-RA conditions. It was not found in PsA.