WEDNESDAY, June 12, 2024 -- The Worst Itch Numeric Rating Scale (WI-NRS) is feasible for assessing the intensity of itch in adults with prurigo nodularis (PN), according to a study published online June 12 in JAMA Dermatology.

Shawn G. Kwatra, M.D., from Johns Hopkins Medical Institutions in Baltimore, and colleagues validated the psychometric properties and determined the clinically meaningful improvement threshold for WI-NRS in patients with moderate-to-severe PN in a secondary analysis of the PRIME and PRIME2 trials. Twenty patients were included across the two studies; 311 were included in the pooled intention-to-treat analysis.

The researchers found that the WI-NRS questions, recall period, and response scale were easy to understand and relevant for patients with PN (20, 19, and 20 of 20 patients, respectively). Between screening and baseline, adequate test-retest reliability was observed. Convergent validity was supported by moderate-to-strong correlations with other conceptually related measures, and discriminant validity was supported by weaker correlations with less-related measures. As demonstrated by differences in change from baseline among groups, WI-NRS was sensitive to change. The clinically meaningful improvement threshold was 4 points using an anchor-based approach with the Patient Global Impression of Severity and Patient Global Impression of Change, which was also supported by distribution-based methods.

"The WI-NRS was found to be a valid and reliable instrument to capture itch data of patients with PN, and a 4-point improvement on WI-NRS may be used to represent a within-patient meaningful improvement in patients with PN," the authors write.

Several authors disclosed ties to pharmaceutical companies, including Sanofi and Regeneron, which funded the study.