Inclusion and exclusion criteria

Studies meeting the following criteria were included: (i) case–control or cross-sectional studies; (ii) studies reporting a comparison of serum visfatin levels between patients with psoriasis and controls; (iii) studies in which all patients were clinically or pathologically diagnosed with psoriasis. The major exclusion criteria were as follows: (i) duplicate or overlapping publications; (ii) review articles, conference abstracts, letters, case reports or animal studies; (iii) studies with incomplete data; (iv) articles not published in English.