Bilirubin Levels and Their Association with Carotid Intima Media Thickness and High-Sensitivity C-reactive Protein in Patients with Psoriasis Vulgaris

Psoriasis vulgaris is associated with an increased risk of atherosclerosis. Carotid intima-media thickness (cIMT) may predict atherosclerosis. We assessed the correlation between bilirubin (a potent endogenous antioxidant) levels and cIMT in patients with psoriasis vulgaris. We also compared the levels of serum total bilirubin (TBil) and its fractions in control subjects and patients with psoriasis. We enrolled 115 participants (60 patients with psoriasis vulgaris and 55 control subjects). The levels of indirect bilirubin were calculated as the difference between TBil and direct bilirubin values. cIMT was measured in both common carotid arteries. TBil levels were lower in patients with psoriasis than in the control group [median (range) 0.55 (0.30-1.23) vs. 0.59 (0.30-1.44) mg/dL] as were indirect bilirubin [0.43 (0.22-1.00) vs. 0.48 (0.25-1.12) mg/dL] and direct bilirubin [0.10 (0.01-0.23) vs. 0.13 (0.03-0.32) mg/dL]. Only direct bilirubin differed significantly (p = 0.0002) but the number of patients with higher values of TBil and indirect bilirubin were significantly greater in the control group (p = 0.0019 by the Fisher's test). The patients with psoriasis had a significantly greater cIMT compared with control subjects (0.54 +/- A 0.08 vs. 0.50 +/- A 0.07 mm, p = 0.005). High-sensitivity C-reactive protein levels were higher in patients with psoriasis compared with controls (2.95 +/- A 3.50 and 0.99 +/- A 0.72 mg/L, p < 0.001). There was a negative correlation between cIMT and TBil levels (r = -0.383, p < 0.01). The results of the correlations were reinforced by multiple regression analysis. To our knowledge, this is the first study to assess the association between TBil and cIMT in patients with psoriasis. Our results support the concept that psoriasis vulgaris is associated with an increased risk of atherosclerosis.