Measurement properties of the Vitiligo Impact Scale-22 (VIS-22), a vitiligo-specific quality-of-life instrument

Abstract

Summary Background Vitiligo has a significant psychological impact which needs to be evaluated separately from the extent of depigmentation. We have developed a vitiligo-specific quality-of-life (QoL) instrument, Vitiligo Impact Scale-22 (VIS-22) for this purpose. Objectives To study the measurement properties of VIS-22 and compare it with the Dermatology Life Quality Index (DLQI) and Skindex-16. Methods Item-reduction analysis was used to reduce the number of items in the original VIS from 27 to 22. The 5-point Physician's Global Assessment (PGA) was used to evaluate the QoL followed by a Visual Analogue Scale (VAS) to assess patient-perceived severity. VIS-22, DLQI and Skindex-16 were self-administered. The validity of the VIS-22 was assessed in 161 patients, reliability in 69 patients and responsiveness in 72 patients and compared with DLQI and Skindex-16. Conclusions VIS-22 is a valid, reliable and responsive QoL instrument. It is comparable to DLQI and Skindex-16 in its measurement properties, while being specific to the needs of patients with vitiligo. What's already known about this topic? Vitiligo has a significant psychosocial burden that needs to be measured separately from the extent of its involvement. Although general and dermatology-specific quality-of-life instruments have been used for this purpose, until recently a vitiligo-specific instrument was not available. What does this study add? The Vitiligo Impact Scale-22 (VIS-22) is a valid, reliable and responsive health-related quality-of-life instrument. It is comparable with the Dermatology Life Quality Index and Skindex-16 in its measurement properties while being specific for patients with vitiligo. Scores on VIS-22 as a whole and responses to individual items can serve as a guide for treatment decisions including psychological intervention. Results Criterion validity was shown by strong correlation of VIS-22 with VAS (r = 0·7076). Convergent validity was evidenced by strong correlations with DLQI (r = 0·71) and Skindex-16 (r = 0·72). Known-groups validity was demonstrated by significantly higher scores in females, those with less education, patients with progressive disease and patients with vitiligo compared with controls (P < 0·001). Reliability was shown by excellent correlation of the scores between baseline and 2 weeks (r = 0·9053). VIS-22 was found to be responsive with scores at 12 weeks moving parallel to scores on VAS. Similar trends were noted with DLQI and Skindex-16.