Validation of the peak pruritus numerical rating scale: Results from clinical studies of dupilumab in adults with moderate-to-severe atopic dermatitis

Objective: To present the validation analyses of the Peak Pruritus Numerical Rating Scale (PP-NRS) for measuring itch in patients with moderate-to-severe atopic dermatitis (AD).
Methods: PP-NRS is a single, self-completed item to assess the intensity of peak (worst) pruritus during the past 24 hours. Content validation included interviews with US adults with AD self-reporting moderate-to-severe itch (n=14). Psychometric evaluation included cross-sectional (construct; known-groups validity) and longitudinal (test-retest; sensitivity to change) analyses. These were assessed in a 16-week phase 2b (P2b) study (N=379; NCT01859988) and confirmed using pooled data from two phase 3 (P3) studies (N=1,379; NCT02277743, NCT02277769) in adults with moderate-to-severe AD.
Results: Interview participants found the PP-NRS relevant, clear, and comprehensive. In P2b large positive baseline correlations were observed between PP-NRS and measures of similar constructs (Average Pruritus NRS [r=1.00], SCORAD itch VAS [r=0.77], Dermatology Life Quality Index (DLQI) itch item [r=0.67], P<0.01 for all), and weak-to-moderate correlations with measures of different constructs (EASI [r=0.09] and Investigator’s Global Assessment (IGA) [r=0.17, P<0.01]), confirmed in P3. PP-NRS differed predictably and significantly across known groups (P<0.0001) in P2b/P3. Intraclass correlation coefficients of the test-retest analysis were ≥0.95 in P2b/P3. Moderate-to-strong correlations of change were observed between PP-NRS and SCORAD itch VAS (P2b/P3; r=0.77/0.73), DLQI itch item (r=0.66/0.64), PCS (r=0.71/0.72), EASI (r=0.50/0.46), and IGA (r=0.50/0.46) (all P<0.01).
Conclusions: Peak Pruritus NRS is a well-defined, reliable, sensitive, and valid scale to assess itch intensity in adult patients with moderate-to-severe AD.
Data first presented at AAD 2017; March 3–7, 2017; Orlando, FL, USA.

Prof. Gil Yosipovitch