Psychometric properties of the itch numeric rating scale, skin pain numeric rating scale, and atopic dermatitis sleep scale in adult patients with moderate-to-severe atopic dermatitis

The test–retest reliability of the Itch NRS, Skin Pain NRS, and ADSS was evidenced by generally large intraclass correlation coefficients (> 0.7) in stable groups of patients between baseline and Week 1 and Weeks 4 and 8. Moderate-to-large correlations (r > 0.4) at baseline and Week 16 were generally observed between each measure and other PROs measuring the same concept, supporting convergent validity. Small-to-moderate correlations with clinician-reported outcomes demonstrated divergent validity. Each instrument was able to distinguish between known groups of disease severity as assessed using other indicators of AD severity. The responsiveness of the Itch NRS, Skin Pain NRS, and ADSS scales was demonstrated through significant differences in their change scores from baseline to Week 16 between categories of change in another PRO also from baseline to Week 16. Thresholds for interpreting meaningful change were estimated as − 4.0 for the 0–10 Itch and Skin Pain NRS items; − 1.25 for the 0–4 ADSS Items 1 and 3 and; − 1.50 for the 0–29 ADSS Item 2, these equivalent to moderate degrees of change.

Trial registration ClinicalTrials.gov numbers: NCT03334396, NCT03334422, and NCT03435081.