Fig. 1

RvD1 levels decreased, while CTGF levels increased in serum of RA patients. RvD1 was determined by UPLC-MS/MS, and CTGF was examined by ELISA kit. a Multiple reaction monitoring (MRM) chromatogram for RvD1 (m/z = 375/141). Q1, M-H (parent ion); Q3, diagnostic ion in the tandem mass spectrometry (MS/MS) (daughter ion). b MS/MS spectrum of RvD1 in serum. c The concentration of RvD1 in serum of RA patients (n = 30) was lower than that of the normal persons (n = 30). d The serum CTGF level from RA patients (n = 30) was significantly increased compared to that from the health controls (n = 30). e Pearson coefficient analysis was used to determine the linear correlation between the concentrations of CTGF and RvD1 in serum (r = − 0.61, p = 0.0003). All data was represented as the mean ± SD. Student’s t test was used to evaluate the statistical significance between the normal and RA group