Quantifying and Tracking Vitiligo

“When determining the effectiveness of a specific treatment for a specific disease, it is important to have a reproducible, validated, pragmatic, and sensitive scoring system .” [1] Traditionally, the job of scoring has fallen to the dermatologist, who has two fairly widely accepted scoring systems available to help monitor vitiligo:  the vitiligo area severity index (VASI) [2] and the vitiligo disease activity score (VIDA) [3].

VASI involves breaking the body into “hand units,” each of which is approximately 1% of the total surface area of the body. Within each hand unit, the degree of depigmentation is estimated and quantized into one of 6 levels. The total VASI is then the sum of the quantized depigmentation levels, where the sum runs over all hand units.

The VIDA is a six-point scale for assessing vitiligo activity based on the individual’s own opinion of the present disease activity over time.

Both VASI and VIDA are convenient approximations in the absence of tools. But why not use tools! Why break the body into “hand units” when you can precisely measure the total surface area affected? Why use a subjective method of tracking changes, when you can do a mathematical alignment of two images?

Once tools are introduced, patients should have access to them, in order to be able to monitor their conditions themselves.

Skinofmine.com has developed a simple system for precisely determining the extent of vitiligo and its progression, based on standard measures and machine learning techniques.  We measure the extent of vitiligo in square millimeters, and use clustering techniques to precisely locate depigmented areas. We take scaling, rotation, and translation into account while determining the best alignment of two images for the purpose of visualizing changes over time.

We do hope these quantification tools will prove useful in the monitoring of vitiligo by patients and doctors alike.

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[1] James Ferguson, MD, FRCP. Published in Journal Watch Dermatology July 28, 2004, covering Arch Dermatol 2004 Jun; 140:677-83

[2] Hamzavi I, Jain H, McLean D, Shapiro J, Zeng H, Lui H. Parametric modeling of narrowband UV-B phototherapy for vitiligo using a novel quantitative tool: The Vitiligo Area Scoring Index. Arch Dermatol 2004;140:677-83.

[3] Njoo MD, Das PK, Bos JD, Westerhof W. Association of the Koebner phenomenon with disease activity and therapeutic responsiveness in Vitiligo Vulgaris. Arch Dermatol 1999;135:407-13.

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