Development and validation of the fingertip unit for assessing Facial Vitiligo Area Scoring Index

Background: Facial involvement of vitiligo is an important factor in a patient's life and has often been evaluated separately from body surface area in clinical trials. However, no reliable tools to measure facial vitiligo specifically are available thus far.

Objective: To develop and validate a practical instrument for assessing facial vitiligo.

Methods: The ratios of a hand to a fingertip unit (FTU) of 98 healthy volunteers (age range, 2-69 years) were calculated to define the FTU. Facial Vitiligo Area Scoring Index was measured as the sum of all FTUs of each vitiligo lesion on the face (range, 0-112 FTU). In the validation study, 6 raters evaluated 11 patients with facial vitiligo twice at an interval of 2 weeks.

Results: One hand was measured at 32.1 ± 1.3 FTU, which was highly consistent among subjects across different age groups, sexes, and races. Facial Vitiligo Area Scoring Index showed remarkably high accuracy (concordance correlation coefficient, 0.946; smallest detectable change, 2.2 FTU) as well as high intrarater reliability (intraclass correlation coefficient, 0.903; inter-rater reliability, 0.903).

Limitations: Lack of dynamic validation of responsiveness.

Conclusion: Facial Vitiligo Area Scoring Index using the FTU is an intuitive, precise, and reliable instrument for assessing the extent of facial involvement in vitiligo patients.