PRTN3 and rheumatoid arthritis: Our analysis confirmed that two bilirubin-derived metabolites (bilirubin degradation product [C16H18N2O5] and bilirubin [E,Z or Z,E]) exhibited negative correlations with DAS28-CRP (ρ < –0.4 and P < 0.05) in both the ACPA– and ACPA+ RA subgroups (Figure 2H; Supplementary Table S7).