Red blood cell distribution width is increased in patients with psoriasis vulgaris: A retrospective study on 261 patients

Circulating inflammatory cytokines and markers are increased in patients with psoriasis. Recent studies have shown that a higher red blood cell distribution width (RDW) is associated with disease activity in various disorders. Our objective was to investigate whether RDW is increased in psoriasis patients, and to evaluate its possible association with disease severity. We conducted a retrospective study of psoriasis patients seen in a university hospital in South Korea. Information about demographics, hematological parameters and disease severity were collected. Statistical analysis was performed using Student's t‐test, multivariable logistic regression, Fisher's exact test and Spearman's rank correlation coefficient analysis as appropriate. A total of 261 psoriasis patients and 102 healthy controls were included in our study. The mean RDW value was significantly increased in psoriasis patients compared with healthy control (P = 0.037). Compared with mild psoriasis patients (Psoriasis Area and Severity Index PASI], <7), moderate to severe patients (PASI, ≥7) showed significantly higher RDW values (P = 0.044). However, RDW did not show significant correlation with PASI (P = 0.358). When patients were divided into two groups according to their RDW value (<14.6% and ≥14.6%), the mean value of PASI was not significantly different (P = 0.219). Patients with psoriasis showed increased RDW values compared with healthy controls. It was also higher in the moderate and severe disease group than the mild group. Though this is only a pilot study, it is possible that RDW value can reflect the inflammatory status of psoriasis patients.