Serum levels of FSTL1 in RA patients before and after treatment. Paired serum samples were obtained from the 20 patients before treatment and after 6 months of treatment with DMARDs and/or infliximab. (A) Fifteen patients achieved at least an ACR20 response. (B) Five nonresponders did not achieve an ACR20 response. Each point represents an individual value. FSTL1, follistatin-like protein 1; RA, rheumatoid arthritis; DMARDs, disease-modifying antirheumatic drugs; ACR20, improvement of ≥20% according to the American College of Rheumatology (ACR) response criteria.