Using the Vitiligo Noticeability Scale in clinical trials: construct validity, interpretability, reliability and acceptability.

Trial participants may assess their vitiligo differently compared with blinded assessors. A VNS score of 3 may be more highly valued by people undergoing vitiligo treatment than was previously thought. What is already known about this topic? Vitiligo is a common condition, and can have a considerable psychological impact. A Vitiligo Core Outcome Set is being developed, to enable the results of vitiligo trials to be compared and combined more easily. The Vitiligo Noticeability Scale (VNS) is a patient-reported outcome measure (PROM) developed in partnership with people with vitiligo; initial validation studies have been promising. What does this study add? The VNS shows good construct validity, reliability and acceptability; it can be used in all ages and skin phototypes. All five levels of the VNS scale should be reported for transparency, to aid interpretation of trial findings, and to facilitate meta-analysis in systematic reviews. VNS assessments made by trial participants and independent observers are likely to be qualitatively different, making blinded assessment of VNS by independent observers difficult to interpret. Blinding of participants to trial interventions is recommended whenever possible. What are the clinical implications of the work? The VNS can be used as a PROM to assess the cosmetic acceptability of repigmentation at individual patches of vitiligo. A VNS score of 3 or more is likely to be valued by patients as a treatment success.