Clinical Significance of Serum Bilirubin in Behçet's Disease

Bilirubin (Bb) is the product of the intravascular compartment of catabolic pathway. In a small number of clinical trials, it has been shown that Bb molecules are associated with cardiovascular diseases, diabetes, cancer, autoimmune (lupus, rheumatoid arthritis) diseases and schizophrenia. Behçet's disease is a chronic, multisystemic, inflammatory vasculitis that was first described by Hulusi Behçet in 1937, which affects almost all organs and systems without any known aetiology. Here, we investigated the clinical significance of serum Bb as a biomarker in the patients with Behçet's disease.

Seventy-one (N = 71) patients with Behcet's diagnosis within the last 1 year were included retrospectively. Control group consisted of 75 subjects with similar age and sex distribution. Serum Bb, indirect Bb, total Bb, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) data were recorded from the hospital records.

In the Behçet group, direct Bb was significantly lower (P = 0.011), ESR and CRP were significantly higher (P = 0.00). No significant differences were observed in other parameters. In the whole group, total Bb and indirect Bb were negatively correlated with ESR (P = 0.025, P = 0.01). Direct Bb was negatively correlated with CRP (P = 0.002). For the diagnosis of Behçet, direct Bb with a threshold of < 0.14 can be used as a diagnostic test (P = 0.000) with 70% sensitivity, 68% specificity (area under the curve = 0.69; 95% confidence interval 0.59-0.80) in ROC curve analysis.

According to our study, we found that inflammatory markers were high and direct Bb values were low in patients with Behcet's disease. In addition, Bb parameters were negatively associated with acute phase reactants. As a practical biomarker with anti-oxidative properties, the direct Bb can be used to diagnose and clinical follow-up in cases with Behçet's disease.