Parametric Modeling of Narrowband UV-B Phototherapy for Vitiligo Using a Novel Quantitative Tool

BACKGROUND: There is currently no quantitative tool for evaluating vitiligo treatment response using parametric methods. OBJECTIVE: To develop and apply a simple clinical tool, the Vitiligo Area Scoring Index (VASI), to model the response of vitiligo to narrowband UV-B (NB-UV-B) phototherapy using parametric tests. DESIGN: Prospective, randomized, controlled, bilateral left-right comparison trial. SETTING: North American tertiary care, university-affiliated phototherapy center. PATIENTS: Patients older than 18 years with stable vitiligo involving at least 5% of their total body surface in a symmetric distribution. INTERVENTION: Treatment with NB-UV-B was given 3 times a week to half of the body on all patients for either 60 treatments or 6 months. The contralateral side served as a no-treatment control. MAIN OUTCOME MEASURE: Repigmentation was assessed using the VASI, which was based on a composite estimate of the overall area of vitiligo patches at baseline and the degree of macular repigmentation within these patches over time. The VASI was validated separately against physician and patient global assessments. The overall reductions in VASI for NB-UV-B and control groups were modeled by multilevel regression with random effects and compared parametrically. RESULTS: The VASI scoring correlated well with both patient and physician global assessments (P =.05 and P<.001, respectively, using ordinal logistic regression). The extent of repigmentation after 6 months on the treated side was 42.9% (95% confidence interval, 26.7%-59.0%) vs 3.3% (95% confidence interval -19.3% to 30.0%) on the untreated side (P<.001). A significant difference between control and NB-UV-B groups was apparent within the first 2 months of therapy. The legs, trunk, and arms were much more likely to repigment than the feet and hands. CONCLUSIONS: The VASI is a quantitative clinical tool that can be used to evaluate vitiligo parametrically. Patients treated with NB-UV-B can be expected to achieve approximately 42.9% repigmentation of their vitiligo after 6 months of treatment, with the greatest response being achieved over the trunk and nonacral portions of the extremities.