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Research Article: Psychometric validation of the Chinese version of the Scratch Intensity and Impact Scale (SIIS) in patients with chronic pruritus

Date Published: 2026-08-17

Abstract:
Chronic pruritus poses a substantial burden on patients, leading to physical discomfort, emotional distress, and psychosocial dysfunction. The Scratch Intensity and Impact Scale (SIIS) is a patient-reported outcome (PRO) measure designed to assess both scratching intensity and its effects on health-related quality of life (HRQoL). However, its psychometric properties have not been validated in a Chinese population. This study aimed to culturally adapt and psychometrically validate the SIIS for Chinese patients with chronic pruritus. The original SIIS was translated into Chinese following a standardized forward-backward translation procedure. In a cross-sectional study, 358 adult patients with chronic pruritus were recruited from Northeast China. Construct validity was assessed by randomly splitting the sample for exploratory factor analysis (EFA; n =?179) with oblique rotation and confirmatory factor analysis (CFA; n =?179). Reliability was evaluated through internal consistency (Cronbach’s ? and McDonald’s ? ), split-half reliability, and two-week test–retest reliability. Content validity was examined using content validity indices. The 13-item Chinese version of the SIIS exhibited a stable two-factor structure, explaining 84.378% of the total variance. Sampling adequacy was confirmed (KMO?=?0.948), and Bartlett’s test indicated suitability for factor analysis (? 2 =?6798.064, p <?0.001). CFA demonstrated acceptable model fit: chi-square degree of freedom ( ? 2 /df)?=?2.094, root mean square error of approximation (RMSEA)?=?0.078, standardized root mean square residual (SRMR)?=?0.0188. Comparative Fit Index (CFI)?=?0.985, Tucker–Lewis Index (TLI)?=?0.981, Normed Fit Index (NFI)?=?0.972, and Incremental Fit Index (IFI)?=?0.985. Content validity was strong, with a scale-level content validity index (S-CVI) of 0.96 and item-level indices (I-CVI) ranging from 0.83 to 1.00. The scale also showed excellent reliability, including high internal consistency (Cronbach’s ? =?0.971, McDonald’s ? =?0.969), split-half reliability (Spearman–Brown coefficient?=?0.904), and strong test–retest stability over 2 weeks ( r =?0.958). The Chinese version of the SIIS demonstrates strong psychometric properties, confirming its reliability and validity as a PRO instrument for evaluating scratching intensity and HRQoL impact. In this population, it shows promise as a PRO instrument for adult patients with chronic pruritus due to AD or psoriasis in dermatology settings, pending further validation in broader populations.

Introduction:
Chronic pruritus poses a substantial burden on patients, leading to physical discomfort, emotional distress, and psychosocial dysfunction. The Scratch Intensity and Impact Scale (SIIS) is a patient-reported outcome (PRO) measure designed to assess both scratching intensity and its effects on health-related quality of life (HRQoL). However, its psychometric properties have not been validated in a Chinese population. This study aimed to culturally adapt and psychometrically validate the SIIS for Chinese patients…

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