Pruritus is the most burdensome symptom of atopic dermatitis (AD). A novel 11-point caregiver-reported worst scratch/itch numeric rating scale (WSI NRS; from 0 [no itching] to 10 [worst itching possible]) to assess pruritus in young patients with moderate-to-severe AD was developed and evaluated. Qualitative interviews were conducted with 24 caregivers of children with AD aged 6 months to <6 years to evaluate content validity. Caregivers understood the WSI NRS and were able to select a response without difficulty. Caregivers endorsed “scratching/itching” as optimal phrasing for their observation of behaviors and representation of their child’s itch severity. Psychometric evaluations of the instrument were performed using data from a Phase 3 study of dupilumab in 161 children (aged 6 months to <6 years) with moderate-to-severe AD (NCT03346434). The test-retest reliability intraclass correlation coefficient (95% CI) was 0.94 (0.89, 0.96), above the recommended 0.70 threshold. The WSI NRS showed moderate to strong correlations with assessed caregiver/patient/clinician-reported clinical outcome assessments (COAs), supporting the convergent and divergent validity of the instrument. The discriminating ability of the WSI NRS was shown by significant differences in WSI NRS scores between patients grouped into COA-based bands. Anchor-based methods supported the use of at least a 2 to 4–point change in WSI NRS as clinically meaningful. These results indicate that the caregiver-reported WSI NRS is a valid, reliable and responsive instrument to assess pruritus in young children with moderate-to-severe AD.
