Validation of Psychometric Properties of the Itch Numeric Rating Scale for Pruritus Associated With Prurigo Nodularis: A Secondary Analysis of a Randomized Clinical Trial

Miriam Kimel; Claudia Zeidler; Paul Kwon; Dennis Revicki; Sonja Ständer

doi:10.1001/jamadermatol.2020.3071

. 2020 Sep 16;156(12):1–5. doi: 10.1001/jamadermatol.2020.3071

Validation of Psychometric Properties of the Itch Numeric Rating Scale for Pruritus Associated With Prurigo Nodularis

A Secondary Analysis of a Randomized Clinical Trial

Miriam Kimel ¹, Claudia Zeidler ², Paul Kwon ³, Dennis Revicki ¹, Sonja Ständer ^2,^✉

¹Evidera Inc, Bethesda, Maryland

²Center for Chronic Pruritus, Department of Dermatology, University Hospital Münster, Münster, Germany

³Menlo Therapeutics Inc, Redwood City, California

Accepted for Publication: June 21, 2020.

^✉

Corresponding Author: Sonja Ständer, MD, Center for Chronic Pruritus, Department of Dermatology, University Hospital Münster, Von-Esmarch-Strasse 58, 48149 Münster, Germany (sonja.staender@uni-muenster.de).

Published Online: September 16, 2020. doi:10.1001/jamadermatol.2020.3071

Author Contributions: Dr Ständer had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Kimel, Kwon, Revicki, Ständer.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Revicki, Ständer.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Kimel, Zeidler, Revicki.

Administrative, technical, or material support: Kwon, Ständer.

Supervision: Kimel, Zeidler, Revicki, Ständer.

Conflict of Interest Disclosures: Dr Kimel received research funding support from Amgen and Menlo Therapeutics. Dr Zeidler has received speaker honoraria/travel fees from Beiersdorf and Dermasence outside the submitted work. Dr Kwon is a former employee of Menlo Therapeutics. Dr Revicki reported grants and personal fees from Takeda during the conduct of the study; grants and personal fees from Amgen and Allergan, grants from Bristol Myers Squibb, and personal fees from Celgene and Alphasigma outside the submitted work; and research funding support from Amgen, Boehringer-Ingelheim, and Menlo Therapeutics. Dr Ständer is an investigator for Dermasence, Galderma, Kiniksa Pharmaceuticals, Menlo Therapeutics, Novartis, Sanofi, Trevi Therapeutics, and Vanda Pharmaceuticals; is a consultant and/or member of the advisory board for Almirall, Bayer, Beiersdorf, BELLUS Health, Bionorica, Cara Therapeutics, Celgene, Clexio Biosciences, DS Biopharma, Galderma, Menlo Therapeutics, Novartis, Perrigo, and Trevi Therapeutics; received other financial support from University Hospital Münster, personal fees from Sonja Ständer, and grants from University Hospital Münster during the conduct of the study; and received personal fees from Cara, Galderma S.A., Kiniksa, Pfizer, Sanofi R&D, and Beiersdorf AG, and grants and personal fees from Trevi outside the submitted work.

Funding/Support: This analysis was funded by Menlo Therapeutics. Menlo Therapeutics supported the preparation and decision to submit the manuscript for publication and participated in review and approval of this manuscript.

Role of the Funder/Sponsor: The data were retrieved from a clinical trial that was designed and conducted by Menlo Therapeutics, including collection, management, analysis, and interpretation of the data. Evidera, Inc, with funding from Menlo Therapeutics, was responsible for the design of the psychometric analysis and data analysis.

Data Sharing Statement: See Supplement 4.

Additional Contributions: Medical writing support for this article was provided by Meredith Rogers, MS, CMPP, of the Lockwood Group, which was in accordance with Good Publication Practice guidelines and funded by Menlo Therapeutics. She was compensated for her work.

^✉

Corresponding author.

PMCID: PMC7495327 PMID: 32936233

Key Points

Question

Is the itch numeric rating scale an appropriate measurement tool for quantifying the extent and intensity of pruritus associated with prurigo nodularis?

Findings

This secondary analysis of a randomized clinical trial of 123 participants found that the Worst Itch Numeric Rating Scale and Average Itch Numeric Rating Scale are acceptable measures of pruritus for patients with prurigo nodularis with good evidence of validity and reliability. This was demonstrated by analyzing test-retest reliability, construct validity, sensitivity to change, and thresholds for meaningful change.

Meaning

The Worst Itch Numeric Rating Scale and Average Itch Numeric Rating Scale should be considered acceptable tools for assessing pruritus in future clinical trials of prurigo nodularis.

This randomized, double-blind study evaluates the psychometric properties of the itch numeric rating scale for measuring severity of pruritis associated with prurigo nodularis.

Abstract

Importance

There is an unmet need for psychometrically sound instruments to measure pruritus associated with prurigo nodularis (PN).

Objective

To evaluate the psychometric properties of the itch numeric rating scale (itch NRS), both the Worst Itch Numeric Rating Scale (WI-NRS) and the Average Itch Numeric Rating Scale (AI-NRS).

Design, Setting, and Participants

This secondary analysis is based on a secondary end point of a phase 2 randomized clinical trial of serlopitant for treatment of pruritus associated with PN. This randomized, double-blind, placebo-controlled study was conducted at 15 sites in Germany. Eligible patients were aged 18 to 80 years and had generalized PN for more than 6 weeks that was refractory to previous antipruritic therapies. Patients were required to have a visual analog scale itch score of 7 or higher at screening. Data were collected from July 2014 to June 2016 and analyzed from June 2016 to January 2017.

Main Outcomes and Measures

The itch NRS (AI-NRS and WI-NRS) was correlated together with the following measures: the electronic verbal rating scale (eVRS) for itch self-categorization, average itch visual analog scale (AI-VAS), worst itch visual analog scale (WI-VAS), the pruritus-specific quality-of-life rating instrument ItchyQoL, Dermatology Life Quality Index (DLQI), and Prurigo Activity and Severity Score (items 7b and 7a: percentage healed prurigo lesions and percentage of prurigo lesions with excoriations).

Results

There were 123 participants in this study; the mean (SD) age of participants was 57.3 (11.58) years, and 58 (47.2%) were male. Strong associations (r ≥ 0.5) were observed between itch NRS items (WI-NRS and AI-NRS) and AI-VAS (24 hours) at weeks 2, 4, and 8 (r = 0.72-0.90; P < .001). Similar strong associations were also observed between itch NRS items and WI-VAS (24 hours) and eVRS for itch severity across weeks 2, 4, and 8 (r = 0.65-0.92; all P < .001). Strong correlations were seen between change scores for WI-NRS and WI-VAS and AI-VAS (r = 0.76 and 0.70, respectively; both P < .001). Similar findings were seen for AI-NRS, where correlations between change scores for WI-VAS and AI-VAS were 0.71 and 0.72, respectively (both P < .001). Analyses for the itch NRS items also showed that test-retest reliability was acceptable and provided evidence of acceptable convergent validity based on the eVRS and visit verbal rating score for itch self-categorization, ItchyQoL, and DLQI.

Conclusions and Relevance

Results from this secondary analysis show that the itch NRS items WI-NRS and AI-NRS have good psychometric properties for pruritus associated with PN and should be considered acceptable tools for assessing pruritus in future clinical trials of PN.

Trial Registration

ClinicalTrials.gov Identifier: NCT02196324

Introduction

Prurigo nodularis (PN), also called chronic nodular prurigo, is a pruritic disease characterized by papulonodular lesions that arise as a consequence of long-term pruritus and scratching.^1,2,3 Pruritus is the dominant symptom, with patients reporting a median intensity of 8 on an 11-point numeric rating scale (NRS).⁴

Because pruritus is a subjective measure, the assessment of any antipruritic treatment effects relies on patients’ reports.³ The NRS for itch (itch NRS) is an instrument intended to measure its intensity³; however, it has not specifically been evaluated for pruritus associated with PN.

The primary objective of this analysis was to evaluate the psychometric properties of the itch NRS score (Average Itch Numeric Rating Score [AI-NRS] and Worst Itch Numeric Rating Score [WI-NRS]) that was included as an end point in a phase 2 study of serlopitant (NCT02196324), an oral neurokinin 1 receptor antagonist, for the treatment of pruritus associated with PN.⁵

Methods

Design and Patients

The methods and results of the phase 2 study have been previously published.⁵ The final version of the trial protocol and the version of trial protocol used for ethics committee approval are presented in Supplement 1 and Supplement 2, respectively. The phase 2 study comprised the analysis and was approved by institutional review board. For this analysis, the patient-reported outcome (PRO)-evaluable population was defined as patients who received at least 1 dose of the study drug and had electronic diary itch NRS data at week 1. Other outcome measures are shown in eTable 1 in Supplement 3.

Statistics

All analyses were conducted using SAS, version 9.2 (SAS Institute). After performing descriptive statistics, the quality criterions of PRO tools (test-retest reliability, construct validity [convergent and discriminant validity], sensitivity to change, and thresholds for meaningful change) were analyzed. For more detailed descriptions of the statistics, see eMethods in Supplement 3.

Results

Patient Population

Baseline demographics and characteristics of the PRO-evaluable population (N = 123) are summarized in Table 1.

Table 1. Patient Demographics and Clinical Characteristics at Baseline.

Characteristic	PRO-evaluable population (N = 123)
Age, mean (SD), y	57.3 (11.58)
Sex, No. (%)
Male	58 (47.2)
Female	65 (52.8)
Duration of prurigo nodularis, No. (%)
≤5 y	60 (48.8)
>5 y	63 (51.2)
AI-NRS, mean (SD)^a^,^b	6.5 (1.83)
WI-NRS, mean (SD)^a^,^b	7.3 (1.67)
AI-VAS, mean (SD)^c	7.9 (1.43)
WI-VAS, mean (SD)^c	8.6 (1.27)
eVRS for itch self-categorization, No. (%)^a^,^d
No itching	0 (0.0)
Mild itching	2 (1.6)
Moderate itching	34 (27.9)
Severe itching	50 (41.0)
Very severe itching	36 (29.5)
DLQI, mean (SD)^e	14.2 (6.76)
ItchyQoL, mean (SD)^f	3.6 (0.71)

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Abbreviations: AI-NRS, Average Itch Numeric Rating Scale; AI-VAS, average itch visual analog scale; DLQI, Dermatology Life Quality Index; eVRS, electronic verbal rating scale; PRO, patient-reported outcome; WI-NRS, Worst Itch Numeric Rating Scale; WI-VAS, worst itch visual analog scale.

^{^a}

The baseline score was defined as the average of the daily scores over the first 7 days of data collected at and after visit 2 (ie, days 1-7; week 1).

^{^b}

Numeric rating scale scores ranged from 0 to 10, with higher scores reflecting worse itch.

^{^c}

Visual analog scale scores ranged from 0 to 100, with higher scores reflecting worse itch.

^{^d}

Values are based on n = 122, as 1 eVRS score was missing.

^{^e}

DLQI scores ranged from 0 to 30, with higher scores reflecting worse influence on quality of life.

^{^f}

ItchyQoL scores ranged from 1 to 5, with higher scores reflecting worse pruritus-specific health-related quality of life impairment.

Convergent and Discriminant Validity

Convergent and discriminant validity test results for WI-NRS and AI-NRS, assessing their associations with other clinical outcome assessments, are summarized in Table 2. Strong associations (r ≥ 0.5) were observed between itch NRS items and average itch visual analog scale (AI-VAS; 24 hours) at weeks 2, 4, and 8 (r = 0.72-0.90; all P < .001). Similar strong associations were also observed between itch NRS items and worse itch visual analog scale (WI-VAS; 24 hours) and electronic Verbal Rating Scale (eVRS) for itch severity items across weeks 2, 4, and 8 (r = 0.65-0.92; all P < .001). Moderate associations were seen between itch NRS items and the pruritus-specific quality of life (QoL) rating instrument ItchyQoL and the Dermatology Life Quality Index (DLQI) (r = 0.36-0.46; all P < .001). In general, weaker associations were observed with percentage of healed prurigo lesions (r = –0.25 to –0.32; P < .01 and P < .001, respectively) and percentage of prurigo lesions with excoriations (r = 0.21-0.28; P < .05 and P < .01, respectively) for itch NRS items at weeks 2 and 4.

Table 2. Construct Validity Results of WI-NRS and AI-NRS With Measures of Itch, Quality of Life, and Prurigo Nodularis Status.

Variable	WI-NRS^a^,^b			AI-NRS^a^,^b
Variable	Week 2	Week 4	Week 8	Week 2	Week 4	Week 8
AI-VAS (24 h)	0.72^c	0.78^c	0.87^c	0.82^c	0.88^c	0.90^c
WI-VAS (24 h)	0.79^c	0.86^c	0.92^c	0.74^c	0.81^c	0.85^c
eVRS^b	0.65^c	0.65^c	0.72^c	0.66^c	0.65^c	0.72^c
ItchyQoL	0.36^c	0.36^c	0.40^c	0.38^c	0.42^c	0.39^c
DLQI	0.40^c	0.42^c	0.46^c	0.41^c	0.45^c	0.45^c
Healed prurigo lesions, %	–0.32^c	–0.27^d	–0.41^c	–0.25^d	–0.28^d	–0.43^c
Prurigo lesions with excoriations, %	0.28^d	0.25^d	0.38^c	0.21^e	0.23^e	0.40^c

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Abbreviations: AI-NRS, Average Itch Numeric Rating Scale; AI-VAS, average itch visual analog scale; DLQI, Dermatology Life Quality Index; eVRS, electronic verbal rating scale; WI-NRS, Worst Itch Numeric Rating Scale; WI-VAS, worst itch visual analog scale.

^{^a}

Spearman correlations.

^{^b}

Weekly mean WI-NRS and eVRS for itch severity scores from the previous week were used for each time point.

^{^c}

P < .001.

^{^d}

P < .01.

^{^e}

P < .05.

Known-Groups Validity

Both WI-NRS and AI-NRS demonstrated significant differentiation among the intensity of itching levels, based on the visit Verbal Rating Scale and eVRS at week 2 (Figure, A and B; lowest P value reported is < .001 for all overall models). As measured by the ItchyQoL and DLQI at week 2, WI-NRS and AI-NRS demonstrated the ability to significantly discriminate among itch-specific QoL levels (Figure, C; P = .01 and P < .01 for overall models, respectively) and dermatology-specific QoL (Figure, D; P < .001 for both overall models). Based on the Prurigo Activity and Severity Scale at week 2, WI-NRS showed significant differentiation among percentage of prurigo lesions with excoriations (P < .05); AI-NRS results were not significant (Figure, E).

Figure. — eVRS indicates electronic Verbal Rating Scale; ItchyQoL, the pruritus-specific quality-of-life rating instrument ItchyQoL; DLQI, Dermatology Life Quality Index; vVRS indicates visit Verbal Rating Scale. Weekly mean itch numeric rating scale (NRS) and electronic verbal rating scale for itch severity scores from the previous week were used to determine WI-NRS and AI-NRS. Both WI-NRS and AI-NRS were assessed using analysis of variance models. A, Mean NRS with visit verbal rating scale (itching) from the visit Patient Global Assessment. The *none* and *mild* categories were combined due to small sample size for the *none* category (n = 1 or 2). B, Mean NRS with electronic verbal rating scale for itch severity. C, Mean NRS with ItchyQoL. D, Mean NRS with Dermatology Life Quality Index (DLQI). E, Mean NRS with percentage of prurigo lesions with excoriations.

Test-Retest Reliability

For the itch NRS, stable patients were defined based on the eVRS. The mean (SD) difference from week 1 to week 2 was –0.5 (0.94) for WI-NRS (P = .002) and –0.4 (1.00) for AI-NRS (P = .01). Corresponding intraclass correlation coefficient values were 0.78 and 0.84, respectively, which demonstrated acceptable agreement between test and retest measures.

Sensitivity to Change

Strong correlations were seen between change scores (week 2 to week 8) for WI-NRS, WI-VAS, and AI-VAS (r = 0.76 and 0.70, respectively; both P < .001). Similar findings were seen for AI-NRS, where correlations between change scores for WI-VAS and AI-VAS were 0.71 and 0.72, respectively (both P < .001). In addition, moderate correlations were seen between change scores for WI-NRS, DLQI, and ItchyQoL (r = 0.40 and 0.45, respectively; both P < .001). Correlations between change scores for AI-NRS and the DLQI and ItchyQoL were 0.46 and 0.45, respectively (both P < .001).

Thresholds for Meaningful Change

For WI-NRS, standard error of the mean values were 1.08 and 1.01 for the intraclass correlation coefficient and 8-week averaged SD and the intraclass correlation coefficient and change score in SD, respectively; corresponding standard error of the mean values were 0.76 and 0.69, respectively, for AI-NRS. These findings suggest that an approximate 1-point change on WI-NRS and AI-NRS may be associated with minimal clinical improvement.

Responder Definitions

A reduction of 2.6 points (37%) in WI-NRS score was associated with at least a moderate improvement in itch based on the visit Patient Global Assessment question, If improved, to what extent?, while a reduction of 3.6 points (53%) was associated with at least a good improvement in itch (eTable 2 in Supplement 3). When eVRS findings were summarized based on any improvement from week 2 to week 8, a reduction of 2.3 points (32%) in WI-NRS score was associated with at least a 1-point improvement in itch category, an improvement of 3.0 points (41%) in WI-NRS score was associated with at least a 2-point improvement in itch category, and an improvement of 4.5 points (62%) in WI-NRS score was associated with at least a 3-point improvement in itch category. Similar findings based on visit Patient Global Assessment and eVRS improvement categories were seen for the AI-NRS.

Discussion

Results from this secondary data analysis of the serlopitant trial⁵ show that the itch NRS items (WI-NRS and AI-NRS) have good psychometric properties for pruritus associated with PN. Analyses for the itch NRS items showed that test-retest reliability was acceptable. Significant correlations were seen between itch NRS items and the other PROs and provided evidence of acceptable convergent validity based on the eVRS, ItchyQoL, and DLQI. It was anticipated that the DLQI would be used to assess discriminant validity as a more general dermatology QoL measure; however, correlations between the itch NRS items were all greater than or equal to 0.40, suggesting that the concepts are more closely related than had been previously hypothesized. In addition, the itch NRS items showed evidence of acceptable known-groups validity and evidence of acceptable sensitivity to change.

Findings from 2 methods of defining responders based on improvement in itch show that WI-NRS change scores of 2.3 to 4.5 are consistent with a 30% to 60% improvement in WI-NRS scores, which could serve as a responder definition in future studies. Previous studies in psoriasis and atopic dermatitis recommend a 4-point WI-NRS response.^6,7,8 The findings of this analysis show that a 3-point or greater improvement in WI-NRS scores from baseline to end point is equivalent to the responder definition. Similar findings were seen for the AI-NRS, suggesting that a 3-point or greater improvement in scores from baseline to end point is equivalent to the responder definition. The similarity in responder definitions for the WI-NRS and AI-NRS is not unexpected, as findings from research in atopic dermatitis and chronic pruritus showed that these measures were highly correlated with each other.^7,9 Additional studies may be needed to confirm the responder definition for these NRS measures in PN.

Limitations

A limitation of this report is that the population comprised only White patients, all of whom were from Germany. Other populations have been shown to interpret their pruritus differently.^10,11

Conclusions

The results of this study fulfill the US Food and Drug Administration’s criteria for an adequate instrument to assess treatment benefit of a given intervention, including evidence supporting reliability, validity, and ability to detect change. Thus, WI-NRS and AI-NRS should be considered acceptable tools for assessing pruritus in future clinical trials of PN.

Supplement 1.

Trial Protocol Version 8

Click here for additional data file.^{(692.4KB, pdf)}

Supplement 2.

Trial Protocol Version 3

Click here for additional data file.^{(687.2KB, pdf)}

Supplement 3.

eMethods (with references)

eTable 1. Outcome Measures Used in the Trial

eTable 2. Meaningful Change Thresholds for WI-NRS and AI-NRS for Defining Responders Using the PGA of Chronic Pruritus and eVRS for Itch Self-Categorization

Click here for additional data file.^{(246.3KB, pdf)}

Supplement 4.

Data Sharing Statement

Click here for additional data file.^{(17.3KB, pdf)}

References

1.Pereira MP, Steinke S, Zeidler C, et al. ; EADV Task Force Pruritus group members . European Academy of Dermatology and Venereology European Prurigo Project: expert consensus on the definition, classification and terminology of chronic prurigo. J Eur Acad Dermatol Venereol. 2018;32(7):1059-1065. doi: 10.1111/jdv.14570 [DOI] [PubMed] [Google Scholar]
2.Zeidler C, Tsianakas A, Pereira M, Ständer H, Yosipovitch G, Ständer S. Chronic prurigo of nodular type: a review. Acta Derm Venereol. 2018;98(2):173-179. doi: 10.2340/00015555-2774 [DOI] [PubMed] [Google Scholar]
3.Ständer S, Augustin M, Reich A, et al. ; International Forum for the Study of Itch Special Interest Group Scoring Itch in Clinical Trials . Pruritus assessment in clinical trials: consensus recommendations from the International Forum for the Study of Itch (IFSI) Special Interest Group Scoring Itch in Clinical Trials. Acta Derm Venereol. 2013;93(5):509-514. doi: 10.2340/00015555-1620 [DOI] [PubMed] [Google Scholar]
4.Iking A, Grundmann S, Chatzigeorgakidis E, Phan NQ, Klein D, Ständer S. Prurigo as a symptom of atopic and non-atopic diseases: aetiological survey in a consecutive cohort of 108 patients. J Eur Acad Dermatol Venereol. 2013;27(5):550-557. doi: 10.1111/j.1468-3083.2012.04481.x [DOI] [PubMed] [Google Scholar]
5.Ständer S, Kwon P, Hirman J, et al. ; TCP-102 Study Group . Serlopitant reduced pruritus in patients with prurigo nodularis in a phase 2, randomized, placebo-controlled trial. J Am Acad Dermatol. 2019;80(5):1395-1402. doi: 10.1016/j.jaad.2019.01.052 [DOI] [PubMed] [Google Scholar]
6.Kimball AB, Naegeli AN, Edson-Heredia E, et al. Psychometric properties of the Itch Numeric Rating Scale in patients with moderate-to-severe plaque psoriasis. Br J Dermatol. 2016;175(1):157-162. doi: 10.1111/bjd.14464 [DOI] [PubMed] [Google Scholar]
7.Yosipovitch G, Reaney M, Mastey V, et al. Peak Pruritus Numerical Rating Scale: psychometric validation and responder definition for assessing itch in moderate-to-severe atopic dermatitis. Br J Dermatol. 2019;181(4):761-769. doi: 10.1111/bjd.17744 [DOI] [PMC free article] [PubMed] [Google Scholar]
8.Ständer S, Luger T, Cappelleri JC, et al. Validation of the Itch Severity Item as a measurement tool for pruritus in patients with psoriasis: results from a phase 3 tofacitinib program. Acta Derm Venereol. 2018;98(3):340-345. doi: 10.2340/00015555-2856 [DOI] [PubMed] [Google Scholar]
9.Verweyen E, Ständer S, Kreitz K, et al. Validation of a comprehensive set of pruritus assessment instruments: The Chronic Pruritus Tools Questionnaire PRURITOOLS. Acta Derm Venereol. 2019;99(7):657-663. doi: 10.2340/00015555-3158 [DOI] [PubMed] [Google Scholar]
10.Shaw FM, Luk KMH, Chen KH, Wrenn G, Chen SC. Racial disparities in the impact of chronic pruritus: a cross-sectional study on quality of life and resource utilization in United States veterans. J Am Acad Dermatol. 2017;77(1):63-69. doi: 10.1016/j.jaad.2017.01.016 [DOI] [PubMed] [Google Scholar]
11.Tey HL, Yosipovitch G. Itch in ethnic populations. Acta Derm Venereol. 2010;90(3):227-234. doi: 10.2340/00015555-0867 [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplement 1.

Trial Protocol Version 8

Click here for additional data file.^{(692.4KB, pdf)}

Supplement 2.

Trial Protocol Version 3

Click here for additional data file.^{(687.2KB, pdf)}

Supplement 3.

eMethods (with references)

eTable 1. Outcome Measures Used in the Trial

eTable 2. Meaningful Change Thresholds for WI-NRS and AI-NRS for Defining Responders Using the PGA of Chronic Pruritus and eVRS for Itch Self-Categorization

Click here for additional data file.^{(246.3KB, pdf)}

Supplement 4.

Data Sharing Statement

Click here for additional data file.^{(17.3KB, pdf)}

[dbr200010r1] 1.Pereira MP, Steinke S, Zeidler C, et al. ; EADV Task Force Pruritus group members . European Academy of Dermatology and Venereology European Prurigo Project: expert consensus on the definition, classification and terminology of chronic prurigo. J Eur Acad Dermatol Venereol. 2018;32(7):1059-1065. doi: 10.1111/jdv.14570 [DOI] [PubMed] [Google Scholar]

[dbr200010r2] 2.Zeidler C, Tsianakas A, Pereira M, Ständer H, Yosipovitch G, Ständer S. Chronic prurigo of nodular type: a review. Acta Derm Venereol. 2018;98(2):173-179. doi: 10.2340/00015555-2774 [DOI] [PubMed] [Google Scholar]

[dbr200010r3] 3.Ständer S, Augustin M, Reich A, et al. ; International Forum for the Study of Itch Special Interest Group Scoring Itch in Clinical Trials . Pruritus assessment in clinical trials: consensus recommendations from the International Forum for the Study of Itch (IFSI) Special Interest Group Scoring Itch in Clinical Trials. Acta Derm Venereol. 2013;93(5):509-514. doi: 10.2340/00015555-1620 [DOI] [PubMed] [Google Scholar]

[dbr200010r4] 4.Iking A, Grundmann S, Chatzigeorgakidis E, Phan NQ, Klein D, Ständer S. Prurigo as a symptom of atopic and non-atopic diseases: aetiological survey in a consecutive cohort of 108 patients. J Eur Acad Dermatol Venereol. 2013;27(5):550-557. doi: 10.1111/j.1468-3083.2012.04481.x [DOI] [PubMed] [Google Scholar]

[dbr200010r5] 5.Ständer S, Kwon P, Hirman J, et al. ; TCP-102 Study Group . Serlopitant reduced pruritus in patients with prurigo nodularis in a phase 2, randomized, placebo-controlled trial. J Am Acad Dermatol. 2019;80(5):1395-1402. doi: 10.1016/j.jaad.2019.01.052 [DOI] [PubMed] [Google Scholar]

[dbr200010r6] 6.Kimball AB, Naegeli AN, Edson-Heredia E, et al. Psychometric properties of the Itch Numeric Rating Scale in patients with moderate-to-severe plaque psoriasis. Br J Dermatol. 2016;175(1):157-162. doi: 10.1111/bjd.14464 [DOI] [PubMed] [Google Scholar]

[dbr200010r7] 7.Yosipovitch G, Reaney M, Mastey V, et al. Peak Pruritus Numerical Rating Scale: psychometric validation and responder definition for assessing itch in moderate-to-severe atopic dermatitis. Br J Dermatol. 2019;181(4):761-769. doi: 10.1111/bjd.17744 [DOI] [PMC free article] [PubMed] [Google Scholar]

[dbr200010r8] 8.Ständer S, Luger T, Cappelleri JC, et al. Validation of the Itch Severity Item as a measurement tool for pruritus in patients with psoriasis: results from a phase 3 tofacitinib program. Acta Derm Venereol. 2018;98(3):340-345. doi: 10.2340/00015555-2856 [DOI] [PubMed] [Google Scholar]

[dbr200010r9] 9.Verweyen E, Ständer S, Kreitz K, et al. Validation of a comprehensive set of pruritus assessment instruments: The Chronic Pruritus Tools Questionnaire PRURITOOLS. Acta Derm Venereol. 2019;99(7):657-663. doi: 10.2340/00015555-3158 [DOI] [PubMed] [Google Scholar]

[dbr200010r10] 10.Shaw FM, Luk KMH, Chen KH, Wrenn G, Chen SC. Racial disparities in the impact of chronic pruritus: a cross-sectional study on quality of life and resource utilization in United States veterans. J Am Acad Dermatol. 2017;77(1):63-69. doi: 10.1016/j.jaad.2017.01.016 [DOI] [PubMed] [Google Scholar]

[dbr200010r11] 11.Tey HL, Yosipovitch G. Itch in ethnic populations. Acta Derm Venereol. 2010;90(3):227-234. doi: 10.2340/00015555-0867 [DOI] [PubMed] [Google Scholar]

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Validation of Psychometric Properties of the Itch Numeric Rating Scale for Pruritus Associated With Prurigo Nodularis

Miriam Kimel, PhD

Claudia Zeidler, MD

Paul Kwon, MD

Dennis Revicki, PhD

Sonja Ständer, MD

Key Points

Question

Findings

Meaning

Abstract

Importance

Objective

Design, Setting, and Participants

Main Outcomes and Measures

Results

Conclusions and Relevance

Trial Registration

Introduction

Methods

Design and Patients

Statistics

Results

Patient Population

Table 1. Patient Demographics and Clinical Characteristics at Baseline.

Convergent and Discriminant Validity

Table 2. Construct Validity Results of WI-NRS and AI-NRS With Measures of Itch, Quality of Life, and Prurigo Nodularis Status.

Known-Groups Validity

Figure. Tests of Known Validity for Worst Itch Numeric Rating Scale (WI-NRS) and Average Itch Numeric Rating Scale (AI-NRS) With Measures of Itch, Quality of Life, and Prurigo Nodularis Status.

Test-Retest Reliability

Sensitivity to Change

Thresholds for Meaningful Change

Responder Definitions

Discussion

Limitations

Conclusions

References

Associated Data

Supplementary Materials

ACTIONS

PERMALINK

RESOURCES

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