Acta Dermato-Venereologica 99-13CompleteContent | Page 23

1288 SHORT COMMUNICATION Minimal Clinically Important Difference in Chronic Pruritus Appears to be Dependent on Baseline Itch Severity Claudia RIEPE 1 , Nani OSADA 1 , Adam REICH 2 , Matthias AUGUSTIN 3 , Claudia ZEIDLER 1 and Sonja STÄNDER 1 * 1 Department of Dermatology and Center for Chronic Pruritus, University Hospital Münster, Von-Esmarch-Strasse 58, DE-48149 Münster, Germany, 2 Department of Dermatology, University of Rzeszow, Rzeszow, Poland, and 3 CVderm, German Center for Health Services Research in Dermatology, Institute for Health Services Research in Dermatology and Nursing, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. *E-mail: [email protected] The minimal clinically important difference (MCID) (1) is the smallest beneficial difference perceived by patients on a scale used for scoring (2, 3). Making a systematic in- vestigation of MCID is demanding because it may depend on the method of calculation, response to an instrument, anchor measure reliability, baseline symptom severity, age, socioeconomic status, education, and treatment (3–5). In a previous study (6), we investigated the overall MCID in chronic pruritus using a visual analogue scale (VAS) and numeric rating scale (NRS). It was found that the MCID corresponded to a 2–3-point decrease in both scales, with no statistically significant difference between them. The second part of the study evaluated the variation in MCID according to baseline pruritus. This study also assessed the influence of sex, pruritus aetiology, skin condition, duration, localization and quality of pruritus on MCID. METHODS The detailed study design is described elsewhere (6). All patients (n = 192) were asked to rate their mean pruritus intensity within 24 h (VAS24h and NRS24h), at baseline (V1), after 5–14 days (V2), and after 28–42 days (V3). At each visit, patients also reported the average (VAS average ) and maximum (VAS max ) pruritus intensity within the previous 4 weeks, as well as completed the Dermatology Life Quality Index (DLQI) and Hospital Anxiety and Depression Scale (HADS-A, HADS-D). At V2 and V3, patients completed a MCID questionnaire with 2 questions: (1) Did your pruritus change in comparison with the first visit (yes/no)? (2) If yes, how did your pruritus change (‘’greatly worsened’’, ‘’worsened’’, ‘’improved’’, ‘’highly improved’’, ‘’all gone’’)? The category ‘’improved’’ was the anchor variable used for MCID calculations for follow-up vi- sits vs. baseline (V1–V2 and V1–V3). Among improved patients, MCID was calculated for 4 VAS 24h and NRS 24h pruritus severity categories (1: 0–2.9 = mild, 2: 3–6.9 = moderate, 3: 7–8.9 = se- vere, 4: 9–10 = very severe pruritus) and for 2 additional VAS 24h categories, i.e. < 7 (weak to moderate pruritus) and ≥ 7 (severe to very severe pruritus). The statistical analysis was performed using SPSS V22.0 for Windows. All data were evaluated descriptively and delineated with standard statistical measures. Before statistical testing, a Kolmogorov–Smirnov test was used to analyse variable distribu- tion. For abnormally distributed samples, a non-parametric test was used (Mann–Whitney for independent and Wilcoxon test for dependent variables between 2 subgroups; Kruskal–Wallis for independent variables between more than 2 subgroups). Multiple pairwise comparisons were performed using the Dunn procedure. For normally distributed samples, a parametric test was used (t-test to compare differences between 2 subgroups; analysis of variance (ANOVA) for more than 2 independent subgroups). Multiple pair- wise comparisons were performed using the Tukey method. The categorical parameter relationships between 2 independent groups were analysed with an χ 2 and Fisher’s exact test, and between 2 related groups via McNemar’s test. The statistical significance was defined as p < 0.05. The study was approved by the local ethics committee (no. 2007- 413-f-S) and registered in the German Clinical Trials Register (DRKS) (no. DRKS00005732). RESULTS At V2 35.94% (n = 69) and 35.42% (n = 68) at V3 (mean 33 days) reported an improvement of the pruritus vs. during previous visits. In this ‘’improved’’ anchor ca- tegory, the mean  ± SD MCID on VAS 24h was 1.40  ±  2.37 (p < 0.001) for V2 vs. V1 (V1–V2) n: 13 33 13 9 9 34 19 7 12 32 13 9 9 33 18 8 and 1.98  ±  2.50 (p < 0.001) for V3 vs. V1 (V1– 6 V3). The corresponding NRS 24h values were 4.56 1.41  ± 2.13 (p < 0.001) and 1.83  ± 2.31 (p < 0.001). 4.38 4.33 4.21 3.65 4 Fig. 1 shows the mean MCID for V1–V2 and 2.92 2.85 2.74 V1–V3 per severity grade, as rated with the 2 VAS 24h and NRS 24h (Fig. 1, Table SI 1 ). 1.34 1.06 0.83 0.46 The differences in VAS 24h and NRS 24h among 0.22 0 0 the severity categories were statistically signifi- -0.04 VAS24h NRS24h VAS24h NRS24h -0.62 cant (p < 0.001) at both time periods. V1-V2 V1-V3 -2 Fig. 2 shows the mean MCID for V1–V2 and V1–V3, as rated with VAS 24h , NRS 24h , DLQI, Pruritus Severity Grade 1: 0-2.9 2: 3-6.9 3: 7-8.9 4: 9-10 -4 HADS-A, and HADS-D in the categories Fig. 1. Mean minimal clinically important difference (MCID) for visit 2 vs. visit 1 VAS 24h < 7 and ≥ 7. The differences between (V1–V2) and for visit 3 vs. visit 1 (V1–V3) per average pruritus severity grade in the the categories VAS 24h < 7 and VAS 24h ≥ 7 were 24 h preceding the corresponding visit, as rated by visual analogue scale (VAS 24h ) and statistically significant considering both the by numeric rating scale (NRS 24h ). Accepted Oct 3, 2019; E-published Oct 3, 2019 doi: 10.2340/00015555-3332 Acta Derm Venereol 2019; 99: 1288–1290 This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica.