Assessment of Vitiligo Lesions Using Polarized Dermoscopy, Sub-Ultraviolet Reflectance Dermoscopy, and Ultraviolet Dermoscopy

This is a single-center, cross-sectional observational imaging study in patients with clinically diagnosed vitiligo.

During a single study visit, demographic and clinical information will be recorded, including disease duration, recent disease course, current treatment status, and patient-reported changes in selected lesions. One to three clinically suitable vitiligo lesions will be included in the main assessment dataset for each participant. Genital lesions will not be evaluated due to practical imaging limitations, hygiene considerations, and participant comfort.

Each selected lesion will be imaged using the Casio DZ-D100-AEA device, which allows simultaneous acquisition of digital contact polarized dermoscopy, digital contact non-polarized dermoscopy, and sub-ultraviolet reflectance dermoscopy images from the same lesion area with a single image capture. This approach is intended to improve within-lesion comparability between polarized dermoscopy and sub-ultraviolet reflectance dermoscopy. Non-polarized images will be obtained as an automatic device output but will not be included in the routine analysis. Ultraviolet fluorescence dermoscopy images will be obtained from the same selected lesion using the DermLite DL5 handheld ultraviolet dermoscope with a smartphone adapter.

For each participant, one lesion will be designated as the index lesion for the primary analysis. If available, the second and third lesions in the main assessment dataset may be used for secondary and exploratory analyses. In participants with more than three imaged lesions, additional lesion images beyond the lesions retained in the main assessment dataset will be assigned to a separate exploratory/calibration image pool and will not be included in the formal main assessment dataset.

The allocation of lesions to the main assessment dataset or the exploratory/calibration pool will be completed before formal image scoring. When more than three lesions are available from a participant, lesions with clearer recent clinical history regarding activity, stability, or repigmentation will be preferentially retained in the main assessment dataset. If several lesions have similarly clear clinical information, allocation will aim to preserve representation of active/progressive, stable, and repigmented/regressive lesions when possible.

The exploratory/calibration image pool will be used for initial exploratory review, refinement of morphological terminology, preparation of evaluator training material, and calibration of scoring rules. These images will not be used as confirmatory evidence for the primary analysis.

Morphological assessment items will be developed from the literature and refined through the calibration process. This process will be used to standardize terminology and scoring rules among dermatologist evaluators before formal image evaluation.

After the scoring form is finalized, coded images from the main assessment dataset will be evaluated by dermatologist evaluators using a 0-3 visibility scoring system. To reduce observer bias, images will be presented without participant identity, lesion code, clinical lesion category, treatment information, or clinical history.

Complete blinding to imaging modality may not be possible because the imaging modalities have characteristic color and light features. This will be considered a methodological limitation. However, the coded and randomized image review process is intended to reduce recognition bias, recall bias, and assessment-order bias.