Increased red blood cell distribution width in patients with plaque psoriasis

Background Red blood cell distribution width (RDW) is frequently increased in inflammatory disorders, and the magnitude of its elevation correlates with disease severity. This study was hence aimed to explore RDW values in patients with psoriasis. Methods The study population consisted of 366 adult patients with mild to severe plaque psoriasis and 366 age- and sex-matched blood donor controls. For each psoriatic patient, demographic, clinical, and laboratory data were regularly collected. Results RDW and MCV were significantly higher in psoriatic patients compared to controls (13.95 vs. 13.40% and 90.4 vs. 89 fL; both p<0.01). In order to assess whether RDW elevations were related to psoriasis severity, we divided our psoriatic patient population into two groups based on a PASI cut-off of 10. No significant differences were observed between the two groups (i.e., PASI>10 and 10) in terms of RDW (p=0.36). Adopting different PASI cut-offs (i.e. 3, 5, 7, 12) did not result in statistically significant differences (p=0.93, 0.48, 0.22, 0.42, respectively). In linear regression analysis, no significant correlation was found between RDW and PASI or CRP, nor with age, gender, or the psoriasis comorbidities listed in Table I. Furthermore, no significant difference in RDW values was noted between psoriatic patients with and without PsA (p=0.27). Conclusions The results of this study confirm that RDW is elevated in psoriatic patients, though the magnitude of its increase did not appear to be associated with disease severity.