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

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.

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.

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.