Otsubo H, et al. - Researchers sought to create a sandwich ELISA system for the measurement of soluble folate receptor β (sFRβ) and assess if baseline levels of serum sFRβ are a biomarker for the rheumatoid arthritis (RA) synovitis activity and response to anti-TNF agents. They evaluated the baseline levels of serum sFRβ before therapy in relation with DAS28-CRP or CRP and response to anti-TNF agents at 3-month follow-up from normal controls (41 samples), patients with OA (29 samples), and patients with RA (27 samples) and synovial fluid sFRβ from patients with RA (17 samples). For the effective response of anti-TNF agents, 100% specificity was seen with high serum sFRβ levels with a cutoff value of 8 ng/mL. In patients with RA, the serum sFRβ levels act as a disease activation biomarker. For the response to anti-TNF agents, high serum sFRβ levels act as a predictive biomarker.