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March 1975

Limited Usefulness of Artificial Light Sources

Arch Dermatol. 1975;111(3):394-395. doi:10.1001/archderm.1975.01630150114018

To the Editor.—  A recent report1 on ultraviolet light sources showed that the ultraviolet output of a solar simulator was similar to the natural spectrum of sunlight. For this reason, investigators are using this artificial light source to evaluate the effectiveness of sun-protective agents prior to sunlight performance tests. Implicit in this method is the assumption that the data obtained with such artificial light sources can be used to predict the results in sunlight tests.A recent study2 with patients having erythropoietic protoporphyria (EPP) compared the ultraviolet protective qualities of orally administered β-carotene in tests using sunlight and a solar simulator. The authors reported that the results showed the qualitative protective effect of β-carotene with either light conditions, but they were concerned about "a lack of more quantitative correlation."We compared their data2 obtained with sunlight and xenon-arc light in the 21 patients who had both tests by comparing the protective factors obtained with each light source (Table). The correlation coefficient for this comparison was

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