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Objective measurement of erythema in psoriasis using digital color photography with color calibration
A Raina1, R Hennessy1, M Rains2
1Biomedical Engineering Department, The University of Texas at Austin, Austin, TX, USA.
Background:
Traditional metrics for evaluating the severity of psoriasis are subjective, which complicates efforts to measure effective treatments in clinical trials.
Methods:
We collected images of psoriasis plaques and calibrated the coloration of the images according to an included color card. Features were extracted from the images and used to train a linear discriminant analysis classifier with cross-validation to automatically classify the degree of erythema. The results were tested against numerical scores obtained by a panel of dermatologists using a standard rating system.
Results:
Quantitative measures of erythema based on the digital color images showed good agreement with subjective assessment of erythema severity (κ = 0.4203). The color calibration process improved the agreement from κ = 0.2364 to κ = 0.4203.
Conclusion:
We propose a method for the objective measurement of the psoriasis severity parameter of erythema and show that the calibration process improved the results.
