For instance, in the ACPA– RA subgroup, biliverdin and bilirubin (Z,Z) were both negatively correlated with ESR (biliverdin: ρ = –0.52 and P = 5.11 × 10–4; bilirubin (Z,Z): ρ = –0.48 and P = 1.73 × 10–3) and CRP (biliverdin: ρ = –0.45 and P = 3.28 × 10–3; bilirubin (Z,Z): ρ = –0.43 and P = 5.19 × 10–3) (Figures 2F–G; Supplementary Tables S5, S6). Here, CRP is linked to rheumatoid arthritis.