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Development and validation of the fingertip unit for assessing Facial Vitiligo Area Scoring Index
Jung Min Bae1, Raheel Zubair2, Hyun Jeong Ju1
1Department of Dermatology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwona, Korea.
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.
