Understanding the Impact of Prurigo Nodularis Itch, Sleep Loss, and Quality of Life

In the Maui Derm NP+PA Fall 2023 poster session “The Sleep Disturbance Numerical Rating Scale: Content validity, psychometric properties, and meaningful within-patient change in people with prurigo nodularis,” researchers wanted to better understand link between loss of sleep and prurigo nodularis (PN). PN is an inflammatory skin condition characterized by itchy, thickened nodules that appear on the extremities and trunk. The intense itching associated with PN significantly affects patients’ quality of life, leading to higher rates of anxiety, depression, and sleep disturbances, particularly during the evening.¹

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While there are no established patient-reported outcome (PRO) measures for quantifying sleep disturbance (SD) in PN, the Sleep Disturbance Numerical Rating Scale (SD NRS) has been utilized in studies to assess day-to-day fluctuations in sleep quality for individuals with pruritic skin disorders. Although the content validity and psychometric properties of this single-item PRO measure have been established in atopic dermatitis (AD), its application in PN has not been explored until now.

To address this gap, researchers conducted qualitative telephone interviews with 21 adults in the US who had been diagnosed with PN and scored ≥4 points on the SD NRS. These interviews combined concept elicitation and cognitive debriefing of the SD NRS. Participants were asked to reflect on the scale change they would expect with a new treatment to perceive a meaningful improvement in their sleep quality.

The findings revealed that all participants experienced sleep disturbance and noted its impact on their daily lives. The majority attributed their sleep disturbances to itchiness, with some identifying it as the most significant challenge posed by PN. Additionally, nearly all participants reported waking up at least once during the night due to PN-related discomfort.

Cognitive debriefing of the SD NRS confirmed that participants understood and could effectively use the scale. The researchers observed that the SD NRS was considered clear, with participants expressing no difficulty in selecting a response. Importantly, participants demonstrated a good understanding of the response options and the recall period specified in the questionnaire.

Further evaluation of the SD NRS using data from a 12-week, phase II clinical trial of nemolizumab in adults with PN reinforced the measure's reliability and validity. Test-retest reliability was substantial, and correlations with other PROs demonstrated the expected patterns of association.

The study ultimately established a threshold of a 4-point change on the SD NRS as indicative of a meaningful within-patient improvement in sleep quality for individuals with PN. These results provide valuable insights into the impact of PN on sleep and underscore the importance of addressing this aspect in the management of the condition. Future research will continue to refine the understanding of the SD NRS and its applications in PN clinical trials.

Reference

1. Ständer S, Fatoumata F, Dias-Barbosa C, et al. The Sleep Disturbance Numerical Rating Scale (SD NRS): Content validity, psychometric properties, and meaningful within-patient change in people with prurigo nodularis. Poster presented at: Maui Derm NP+PA Fall 2023; September 27-30, 2023; Asheville, NC.