Fig. 4

Box and whisker plots of selected biomarker candidates in healthy controls and rheumatoid arthritis (RA) patients. Proteins altered among RA patients relative to the healthy controls were selected. a–d Angiotensinogen, serum amyloid A-4 protein (SAA4), retinol-binding protein-4 (RBP4), and vitamin D-binding protein (VDBP) profiles were compared between healthy controls and RA patients. The number of healthy controls and RA patients was 251 and 230, respectively. Box plots represent the upper quartile, lower quartile, and median (horizontal line). Whiskers enclose the range (min-max value). Independent samples t tests were used to determine the statistical significance **p < 0.001. AUC, area under the curve