British Journal of Dermatology | 2021
P26: Using the Vitiligo Noticeability Scale in clinical trials and clinical practice: construct validity, interpretability, reliability and acceptability
Abstract
P26 Using the Vitiligo Noticeability Scale in clinical trials and clinical practice: construct validity, interpretability, reliability and acceptability J. Batchelor, S. Gran, P. Leighton, L. Howells, A. Montgomery, W. Tan and K. Thomas University of Nottingham, Nottingham, UK Systematic reviews have identified many vitiligo trials, but these use different and often unvalidated outcome measures, preventing the combination of results in meta-analyses and leading to research waste. To address this problem, a vitiligo core outcome set (VCOS) is being developed. Core outcome sets are internationally agreed minimum sets of high-quality, validated outcome measurement instruments that should be used in clinical trials for specific conditions. Their adoption improves trial design and allows meta-analysis of data from different trials, generating better-quality evidence to support patient care. Valid and reliable outcome measures are needed for the VCOS. We previously developed the Vitiligo Noticeability Scale (VNS) as a patient-reported outcome measure to assess one of the domains in the VCOS: cosmetic acceptability of repigmentation achieved with vitiligo treatment. When developing the VNS we used digitally generated images to show different levels of repigmentation. In this research, we used a large database of clinical images of vitiligo from the HI-Light Vitiligo trial, in order to assess the construct validity, interpretability, test–retest reliability and acceptability of the VNS. We used image pairs of vitiligo patches before and after treatment, plus VNS and other outcome data, from the HILight trial. We compared these with outcome assessments for the same image pairs made by clinicians and people with vitiligo who were not trial participants. We conducted hypothesis testing to assess psychometric properties of the VNS, using kappa statistics to assess agreement between outcome measures. We also ran three focus groups and an online discussion group to gain qualitative feedback on how the VNS is used by people with vitiligo. Our hypothesis that there would be a positive association between VNS and global treatment success at end of treatment was supported. The kappa statistic ranged from 0 41 to 0 91, depending on the VNS score used to define treatment success. A VNS score of 3 (partial treatment response) may be more highly valued by people undergoing vitiligo treatment than previously thought. Age and skin phototype did not influence interpretation of the VNS scores. Other analyses confirmed VNS test–retest reliability (weighted kappa 0 73). Clinician-rated percentage repigmentation > 75% also showed good agreement with global treatment success (kappa 0 80). In the focus groups, people with vitiligo confirmed the VNS to be an acceptable and meaningful assessment. These findings support the case for including the VNS in the VCOS for the domain of ‘cosmetically acceptable repigmentation’.