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Comparing Quantitative Measures of Erythema, Pigmentation and Skin Response using Reflectometry

Authors


*Address reprint requests to Dr Mark D. Shriver, Department of Anthropology, Pennsylvania State University, 409 Carpenter Building, University Park, PA 16802, USA. E-mail: mds17@psu.edu

Abstract

We measured a number of pigmentation and skin response phenotypes in a sample of volunteers (n=397) living in State College, PA. The majority of this sample was composed of four groups based on stated ancestry: African-American, European-American, Hispanic and East Asian. Several measures of melanin concentration (L*, melanin index and adjusted melanin index) were estimated by diffuse reflectance spectroscopy and compared. The efficacy of these measures for assessing constitutive pigmentation and melanogenic dose–response was evaluated. Similarly, several measures of erythema (a*, erythema index and adjusted erythema index) were compared and evaluated in their efficacy in measuring erythema and erythemal dose–response. We show a high correspondence among all of the measures for the assessment of constitutive pigmentation and baseline erythema. However, our results demonstrate that evaluating melanogenic dose–response is highly dependent on the summary statistic used: while L* is a valid measure of constitutive pigmentation it is not an effective measure of melanogenic dose–response. Our results also confirm the use of a*, as it is shown to be highly correlated with the adjusted erythema index, a more advanced measure of erythema based on the apparent absorbance. Diffuse reflectance spectroscopy can be used to quantify the constitutive pigmentation, melanogenic dose–response at 7 d and erythemal dose–response at both 24 h and 7 d postexposure.

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