The Role of Bilirubin in Rheumatoid Arthritis as a Biomarker

INTRODUCTION: Serum bilirubin (Bb) has an anti-inflammatory biologic effect through its antioxidant component. The present study aims to reveal the importance of serum Bb in Rheumatoid arthritis (RA) as a biomarker.

METHODS: This study was designed as a case-control study. Seventy-five RA patients with age (p=0.31) and gender matched 75 controls were included in this study. Clinical characteristics and laboratory parameters were analyzed retrospectively. Serum direct Bb (DBb), indirect Bb (InBb), total Bb (TBb), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) data were recorded. Disease activity in RA was assessed using the Disease Activity Score 28 (DAS28).

RESULTS: In this study, acute phase reactants, CRP (p<0.01) and ESR (p<0.01) were significantly higher in our study group; DBb was found significantly lower (p<0.01) than the control group. ESR was negatively correlated with DBb, InBb and TBb respectively (p=0.029, r=-0.252; p=0.003; r=- 0.362; p=0.009, r=-0.302). TBb was not correlated with DAS 28 (p=0.08; r=-0.203).
DISCUSSION AND CONCLUSION: We found that DBb was significantly lower in RA patients than the patients in the control group. All Bb parameters were negatively correlated with acute phase reactants and DAS28. As a practical biomarker with anti-oxidative properties, the DBb can be used in clinical follow-up in RA.