OBJECTIVES: To explore the relevance of itch to adults and adolescents with atopic dermatitis (AD) and assess validity of the Itch Numerical Rating Scale (NRS).

METHODS: A mixed-methods study consisting of concept elicitation (CE) interviews, 2-week daily diary, and cognitive interviews (CI) of adults and adolescents (≥12 years) with AD. The Itch NRS asked about “worst itching” in the past 24 hours on an 11-point scale (0 [no itch] – 10 [worst itch imaginable]). The qualitative and quantitative data were analyzed.

RESULTS: Itch was the most common symptom reported in AD. All participants (N=44) confirmed relevance of itch as a concept; 43/44 agreed on the wording, understanding of the response scale, and correctly referred to the 24-hour recall period when discussing their responses. Of the 15 participants probed, 13 incorrectly reported their “average” itch with several describing their chosen response as the severity of their itch compared to their worst-ever itch. These findings align with participants’ suggestion that “worst itch” be defined (eg, “rate your itching severity by circling the number that best describes your worst level of itching…”).

Quantitative diary data demonstrated acceptable psychometric performance. Participants utilized the majority of the response scale on ≥1 days, with an even distribution across response options. Day 7 (test) versus Day 14 (retest) reliability was high, with an observed intraclass correlation coefficient=0.94 among stable participants. Concurrent validity was acceptable, with strong correlations (0.55–0.76) observed with other diary AD symptom measures. There were no major overall differences between adults and adolescents.

CONCLUSIONS: Adults and adolescents noted that the Itch NRS was easy to understand and relevant to their AD experiences, with clear alignment between item wording and language used by participants. Psychometrically, the Itch NRS was a valid and reliable measure of itch that applied to both adults and adolescents.