Qualitative analysis and reproducibility assessment of the Scalp Itch Numeric Rating Scale among patients with moderate to severe plaque psoriasis of the scalp

AbstractBackground: Pruritus is a prevalent and bothersome symptom of scalppsoriasis. Validated scales assessing scalp itchare needed to evaluate treatment efficacy.Objective: To evaluate comprehensibility and reproducibility of the Scalp ItchNumeric Rating Scale (NRS), a novel scale being used in a phase 3 study of apremilast.Methods: The Scalp ItchNRS, Modified Whole Body ItchNRS, Global Assessment of Psoriasis Severity- Scalp(GAPS-S), and Global Impression of Change- Scalp Itch(GIC-SI) were assessed among patients with moderate to severe scalppsoriasis. Convergent validityand test–retest reliability between two visits (7 ± 3 days apart) were assessed using intra-class and Spearman’s correlations.Results: Patients found the Scalp ItchNRS easy to use and understand. Convergent validity(Modified Whole Body ItchNRS Visit 1: rs = 0.71, Visit 2: rs = 0.92, p< .0001; GAPS-S Visit 1: rs = 0.62, Visit 2: rs = 0.63, p< .0001), and consistency with changes (Modified Whole Body ItchNRS: rs = 0.69, p< .0...