SHORT COMMUNICATION 759
ActaDV ActaDV
Advances in dermatology and venereology Acta Dermato-Venereologica
Tailoring the Cut-off Values of the Visual Analogue Scale and Numeric Rating Scale in Itch Assessment
Adam REICH 1, Evangelos CHATZIGEORKIDIS 2, Claudia ZEIDLER 2, Nani OSADA 2, Masutaka FURUE 3, Kenji TAKAMORI 4, Toshi EBATA 5, Matthias AUGUSTIN 6, Jacek C. SZEPIETOWSKI 1 and Sonja STÄNDER 2
1
Department of Dermatology, Venereology and Allergology, Wroclaw Medical University, Ul. Chałubińskiego 1, 50-368 Wrocław, Poland,
2
Department of Dermatology and Competence Center Chronic Pruritus( KCP), University Hospital Münster, Münster, Germany, 3 Department of Dermatology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 4 Institute for Environmental and Gender Specific Medicine and Department of Dermatology, Juntendo University Graduate School of Medicine, Urayasu, Chiba, 5 Department of Dermatology, The Jikei University School of Medicine, Chitofuna Dermatology Clinic, Tokyo, Japan, and 6 Institute for Health Services Research in Dermatology and Nursing, University Medical Center Hamburg, Hamburg, Germany. E-mail: adi _ medicalis @ go2. pl Accepted Feb 20, 2017; Epub ahead of print Feb 22, 2017
Itch is a common symptom in many dermatological patients, but also in various systemic, neurological and psychiatric conditions. However, due to its subjective nature, an objective measurement of itch severity represents a significant challenge both in routine daily practice and in clinical trials( 1). Several different instruments and methods have been used in itch studies in the past; however, none can currently be considered as a gold standard. Unidimensional itch intensity scales, such as the visual analogue scale( VAS), the numeric rating scale( NRS) or the verbal rating scale( VRS) are the most widely used due to their simplicity and rapidity( 2, 3). Recently published data have also suggested that, aside from some limitations, these instruments provide valid and reliable values of itch evaluation( 2 – 8). They showed good convergent and content validity and good test – retest reproducibility as well as responsiveness to change in itch assessment( 2 – 8).
Briefly, the VAS is a 10-cm long line on which patients mark their pruritus intensity on a scale from“ no itch”( 0 points) to“ worst imaginable itch”( 10 points)( 9). The NRS is similar to the VAS method but assess pruritus intensity as a number from 0 to 10( 1). In turn, the VRS is coded with graduated adjectives( usually ranging from“ no itch” to“ severe” or“ very severe itch”)( 1). In 2012 we suggested a provisional categorization of VAS scores( 3), supported by the results of Kido-Nakahara et al.( 5). Here, we have provided further data on VAS and NRS categorization, based on a large, population-based study performed within the special interest group“ Scoring Itch in Clinical Trials” of the International Forum for the Study of Itch( IFSI).
MATERIALS AND METHODS
Data for 1,666 patients with various chronic itchy conditions were extracted from a local, prospectively collecting database( 10). In detail, basic socio-demographic data, clinical data, and first- and follow-up visit itch intensity ratings( VAS, NRS and VRS) were assessed. The patients performed 5,620 assessments of pruritus intensity( up to 9 assessments per patient). Detailed characteristics of participating subjects are shown in Table SI 1.
1 https:// www. medicaljournals. se / acta / content / abstract / 10.2340 / 00015555-2642
Determination of the VAS and NRS categories was performed as described previously( 3). The κ coefficient of agreement was calculated for VRS and various sets of bands of the VAS and NRS scores. The following assumptions regarding κ coefficient were made: < 0 no agreement, 0 – 0.2 slight, 0.21 – 0.4 fair, 0.41 – 0.6 moderate, 0.61 – 0.8 substantial, and 0.81 – 1 almost perfect agreement. In addition, the Spearman’ s rank correlation coefficients between the VRS and individual sets of bands of the VAS and NRS were determined.
RESULTS
All participants assessed their pruritus with VRS at all time-points. There were 5( 0.1 %) missing values in the NRS scoring and 79( 1.4 %) in the VAS scoring. According to the VRS, at 466( 8.3 %) assessments patients reported no itch during the day of examination, at 2,276( 40.5 %) assessments patients reported mild itch, at 2,239( 39.8 %) assessments patients reported from moderate itch, and at the remaining 639( 11.4 %) assessments from severe / very severe itch. Itch intensity was scored slightly, albeit significantly higher with the NRS( mean: 4.7 ± 2.8 points) than with the VAS( mean: 4.4 ± 3.1 points)( paired Student’ s t-test: p < 0.001). Highly significant correlations were observed between each of the scales used for itch assessment( VRS and VAS ρ = 0.83, p < 0.001; VRS and NRS: ρ = 0.85, p < 0.001; VAS and NRS: ρ = 0.91, p < 0.001).
Statistical analysis( calculated κ coefficient of agreement and correlation coefficients) found that the cut-offs for 3-7-9 provided both high correlation coefficients [ VAS: κ = 0.692( 95 % CI: 0.678 – 0.706), ρ = 0.803; NRS: κ = 0.649( 95 % CI: 0.634 – 0.664), ρ = 0.794 ] and reliable mean values( mild pruritus, mean VAS / NRS: 1.4 ± 0.7 / 1.6 ± 0.5 points; moderate pruritus: 4.7 ± 1.1 / 4.3 ± 1.1 points; severe pruritus: 7.8 ± 0.6 / 7.5 ± 0.5 points; very severe pruritus: 9.6 ± 0.4 / 9.5 ± 0.5) in the investigated collective. Good correlation coefficients of the cut offs of 4-6-9 and 4-7-9 were also found( Table SII 1).
DISCUSSION
A robust development of new anti-pruritic treatment strategies are, at least partly, limited by difficulties in the assessment of their effectiveness. In this study we
This is an open access article under the CC BY-NC license. www. medicaljournals. se / acta Journal Compilation © 2017 Acta Dermato-Venereologica. doi: 10.2340 / 00015555-2642 Acta Derm Venereol 2017; 97: 759 – 760