Systemic Immune-Inflammation Index (SII) Predicts Increased Severity in Psoriasis and Psoriatic Arthritis

Background: Psoriasis is a common chronic inflammatory dermatosis. Systemic immune inflammation index (SII) is an inflammation-based biomarker, which has been shown to be an effective prognostic factor in diseases with an inflammation-related etiology. Objectives: The aim of the present study was to investigate the potential efficacy of SII as a prognostic factor in patients with psoriasis and psoriatic arthritis. Materials and methods: This is a study developed based on the analysis of the medical records of patients with psoriasis. The study retrospectively evaluated the records of the participants for complete blood count results. The SII was calculated by the formula: neutrophil x platelet/lymphocyte. Neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR) and platelet-lymphocyte ratio (PLR) were determined. Results: SII was significantly higher in patients with psoriasis than in controls (578.1 vs. 396, p<0.001). The differences between the median NLR (2.2 vs. 1.5, p<0.001), MLR (0.25 vs. 0.21, p<0.001) and the mean red cell distribution width coefficient of variation (13.8 vs. 12.8, p<0.001) values of patient and control group were significant. SII was higher in patients with moderate/severe psoriasis than patients with mild psoriasis (687.3 vs. 506.6, p=0.034). A positive correlation was observed between SII and PASI (p<0.001; r=0.37). SII was higher in patients with arthritis than patients without (672.1 vs. 548.2, p=0.018). Conclusion: This is the first study to prove that SII might serve as an independent prognostic indicator for patients with psoriasis and psoriatic arthritis.