Abstract
BackgroundChronic kidney disease-associated pruritus (CKD-aP) is characterized by persistent itch that often leads to substantially impaired quality of life. The Worst Itching Intensity Numerical Rating Scale (WI-NRS) is a single-item patient-reported outcome measure in which patients indicate the intensity of the worst itching they experienced over the past 24 h. Here, we evaluated the content validity and psychometric properties of the WI-NRS and confirmed the threshold of meaningful change in hemodialysis patients with moderate-to-severe CKD-aP.MethodsContent validity interviews were conducted in 23 patients. Psychometric properties of the WI-NRS were assessed using data from one phase 2 (N = 174) and two phase 3 (N = 848) clinical trials investigating an anti-pruritic treatment. Anchor-based methods were used to confirm meaningful within-patient change score thresholds in the phase 3 trial patients and mixed-method exit interviews (N = 70) contributed further insight.ResultsContent validity interviews indicated patients considered the WI-NRS to be straightforward, comprehensive, and relevant. Test–retest reliability was strong in both trial cohorts (intraclass correlation coefficients > 0.75). Construct validity analyses indicated high correlation between the WI-NRS and other measures of itch. Anchor-based analyses showed a reduction of ≥ 3 points from baseline score represented an appropriate clinically meaningful within-patient change on the WI-NRS. In the exit interviews, all patients with a reduction ≥ 3 points considered the change meaningful.ConclusionsThe WI-NRS is a reliable, valid, and responsive measure of itch intensity for patients with moderate-to-severe CKD-aP. These results support its use to assess treatment efficacy and in clinical evaluation and management of pruritus in hemodialysis patients.
Highlights
Chronic kidney disease-associated pruritus (CKD-aP) is characterized by persistent itch that often leads to substantially impaired quality of life
Using data from three clinical trials of a novel treatment for itch in patients undergoing hemodialysis with moderate-to-severe pruritus, we found that the scale was reliable in repeat-testing experiments, and mirrored other methods of measuring changes in itch
Our analysis and patients’ opinions showed a 3-point reduction in itch intensity on the scale represented a meaningful improvement. These findings support the use of this scale to assess the efficacy of new treatments and in clinical evaluation and management of pruritus in patients with chronic kidney disease
Summary
Chronic kidney disease-associated pruritus (CKD-aP) is characterized by persistent itch that often leads to substantially impaired quality of life. Pruritus is one of the most common and distressing symptoms in patients with chronic kidney disease receiving hemodialysis [1,2,3,4]. Chronic kidney disease-associated pruritus (CKD-aP) does not originate from skin lesions, but rather is a systemic, persistent itch sensation that often leads to considerable mechanical skin damage due to a continuous and uncontrollable urge to scratch [5, 6]. Patients with CKD-aP suffer severely impaired health-related quality of life (HRQoL), including sleep disturbance, chronic fatigue, agitation, shame, social isolation, and depression [1, 3, 7, 8, 10, 11]. The pruritus tends not to be adequately controlled by topical emollients, antihistamines, or steroids or off-label used treatment, like gabapentin, which are not always well tolerated [2, 8]
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