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. 2023 Jul;13(7):1587-1602.
doi: 10.1007/s13555-023-00962-8. Epub 2023 Jun 17.

The Sleep Disturbance Numerical Rating Scale: Content Validity, Psychometric Validation, and Meaningful Within-Patient Change in Prurigo Nodularis

Sonja Ständer  1 , Fatoumata Fofana  2 , Carla Dias-Barbosa  3 , Danielle Rodriguez  4 , Ismail Budhiarso  4 , Zarif K Jabbar-Lopez  5 , Christophe Piketty  5 , Margaret Vernon  6 , Jorge Puelles  7
Affiliations

The Sleep Disturbance Numerical Rating Scale: Content Validity, Psychometric Validation, and Meaningful Within-Patient Change in Prurigo Nodularis

Sonja Ständer et al. Dermatol Ther (Heidelb). 2023 Jul.

Abstract

Introduction: Sleep is often disturbed in patients with prurigo nodularis (PN). To address the lack of validated patient-reported outcome (PRO) measures for quantifying sleep disturbance in PN, we evaluated the Sleep Disturbance Numerical Rating Scale (SD NRS) as a single-item PRO measure for quantifying sleep disturbance in PN.

Methods: Adults with PN participated in qualitative interviews, which included concept elicitation and cognitive debriefing of the SD NRS. The SD NRS was evaluated psychometrically using data from a phase 2 randomized trial in adults with PN (NCT03181503). Other PRO assessments included the Average Pruritus (AP) NRS, AP Verbal Rating Scale (VRS), peak pruritus (PP) NRS, PP VRS, and Dermatology Life Quality Index (DLQI). Reliability, validity, and responsiveness of the SD NRS were evaluated, and meaningful within-patient change was estimated from qualitative interview responses and quantitative trial data.

Results: All interview participants (N = 21) experienced sleep disturbance and most (95%) understood the SD NRS as intended. The SD NRS demonstrated test-retest reliability based on intra-class correlation coefficients for itch-stable participants of 0.87 for the AP VRS and 0.76 for the PP VRS. At baseline, Spearman's rank-order correlation coefficients were moderate to strong (0.3-0.8) between the SD NRS and the AP NRS, AP VRS, PP NRS, PP VRS, and DLQI. Known-groups validity was demonstrated by higher (worse) SD NRS scores in participants with worse scores on the AP NRS, AP VRS, PP VRS, and DLQI. Improvements in SD NRS scores were greater in participants classified as "improved" versus "worsened/unchanged" on the anchor PROs. A 2- to 4-point decrease on the 11-point SD NRS scale was identified as a meaningful within-patient change.

Conclusion: The SD NRS is a well-defined, reliable, and valid PRO measure that can be used in daily practice and clinical trials to capture sleep disturbance in adults with PN.

Keywords: Nodular prurigo; Outcome measurement; Patients; Qualitative research; Quality of life.

Plain language summary

Patients with the skin disease prurigo nodularis often sleep badly because their skin is very itchy in the evening and at night. In assessing the effectiveness of new treatments for prurigo nodularis, it is useful to know whether patients sleep better when taking them. Here, we tested whether the “Sleep Disturbance Numerical Rating Scale” (SD NRS), a tool for measuring sleep, can be used by patients with prurigo nodularis. The SD NRS asks patients to score their sleep loss during the previous night on a scale of 0 (“no sleep loss”) to 10 (“I did not sleep at all”). When we interviewed 21 patients with prurigo nodularis, 19 of them had problems falling asleep and 18 of them woke up every night. Most of the patients found the SD NRS easy to use. To further explore whether the SD NRS is suitable for patients with prurigo nodularis, we also analyzed data from a European clinical study in which patients with prurigo nodularis received nemolizumab, a new treatment being developed for the disease. Patients completed the SD NRS each morning during the clinical study. We found that the SD NRS has the necessary properties to be useful for assessing sleep on a daily basis. We also determined that a 2- to 4-point decrease on the SD NRS scale would represent a meaningful improvement in sleep for patients with prurigo nodularis. We conclude that the SD NRS is a useful tool for assessing sleep in prurigo nodularis patients participating in clinical studies.

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Conflict of interest statement

Sonja Ständer has received grants/contracts from Almirall, Beiersdorf, the German Research Foundation (DFG), the European Academy of Dermatology and Venereology (EADV), the German Federal Ministry of Education and Research (BMBF), the Interdisciplinary Center for Clinical Research Münster (IZKF), Leo Pharma, Menlo, Novartis, Sanofi, and Trevi Therapeutics; consulting fees from Abbvie, Almirall, Beiersdorf, Bellus Health, Benevolent, Bionorica, Cara, Celgene, CelloHealth, Clexio, DS Biopharma, Eli Lilly, Escient, Galderma, Grünenthal, Kiniksa, Klinge Pharma, Menlo, Sanofi, Sienna, Trevi, the P.G. Unna Academy, Perrigo, Pfizer, Vanda, Vifor, and WebMD; and payment/honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events from Almirall, Eli Lilly, Sanofi, Galderma, Menlo, Omnicuris, Beiersdorf, Leo Pharma, Novartis, the P. G. Unna Academy, Pfizer, and Pierre Fabre. She has also participated in advisory boards for AbbVie, Almirall, Beiersdorf, Bellus Health, Benevolent, Bionorica, Cara, Celgene, CelloHealth, Clexio, DS Biopharma, Eli Lilly, Escient, Galderma, Grünenthal, Kiniksa, Klinge Pharma, Menlo, Sanofi, Sienna, Trevi, the P.G. Unna Academy, Perrigo, Pfizer, Vanda, Vifor, and WebMD. Fatoumata Fofana, Carla Dias-Barbosa, Danielle Rodriguez, Ismail Budhiarso, and Margaret Vernon are employees of Evidera, which was contracted by Galderma for the purposes of this study. Zarif K. Jabbar-Lopez, Christophe Piketty, and Jorge Puelles are employees of Galderma, which is currently sponsoring the development of nemolizumab for the treatment of prurigo nodularis.

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