Psychometric evaluation of the Worst Pruritus Numerical Rating Scale (NRS), Atopic Dermatitis Symptom Scale (ADerm-SS), and Atopic Dermatitis Impact Scale (ADerm-IS)

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritus, skin pain, and sleep impacts, which are only reportable by patients themselves. The goal of this research is to evaluate the reliability, validity, and interpretability of the scores from three patient-reported outcome measures within the context of a clinical trial for adolescents and adults with moderate to severe AD.

Methods: Data from a Phase 3 randomized, double-blind, placebo-controlled, multinational clinical trial for individuals 12-75 years of age with moderate to severe AD (AD Up [ClinicalTrials.gov NCT03568318]) were used to assess the reliability, validity, and interpretability of scores on the Worst Pruritus Numerical Rating Scale (NRS) and the Atopic Dermatitis Symptom and Impact Scales (ADerm-SS and ADerm-IS). Analyses were conducted separately for the adult and adolescent subgroups.

Results: Of the 882 participants included in the psychometric analyses, the majority were adults (n = 769, 87.2%), male (n = 536, 60.8%), and white (n = 630, 71.4%). Multi-item scores from the ADerm-SS and ADerm-IS had good internal consistency reliability, and most scores demonstrated acceptable test-retest reliability. Scores from the three questionnaires demonstrated adequate validity, exhibiting correlations with other conceptually related outcome assessments and score differences between clinically distinct subgroups. Finally, the score interpretation analyses provide estimates for meaningful within-person change and between-groups difference thresholds that may be useful for future research in adults and adolescents with moderate to severe AD.

Conclusions: These results provide evidence that the scores produced by the Worst Pruritus NRS, ADerm-SS, and ADerm-IS are reliable and construct-valid when completed by adults and adolescents with moderate to severe AD in a clinical trial setting. The results presented here expand upon the previous qualitative evidence of these tools and provide further support for their use in future clinical studies. While results are specific to clinical trials, next steps would be to evaluate the use of these questionnaires in clinical practice. This can provide clinicians and dermatologists a window into the patient's disease experience outside of the clinic, aid in shared decision making, and support a patient-centric approach to management of moderate to severe AD.