The standard vasoconstrictor assay has been of proven value in ranking the potencies of topically applied corticosteroids from alcoholic solutions. Shortening the time of application, omitting occlusion, and using multiple reading times has allowed valuable observations to be made on the effective delivery of corticosteroids from their vehicles. As with any biologic assay, substantial variation does occur. These inherent errors may be reduced by preselection of subjects and the use of sufficient numbers of subjects and sites. Interpretive errors can be reduced by using two independent readers, randomization of the test materials, the use of a patterned square site, and standard lighting conditions.
Burdick KH. Various Vagaries of Vasoconstriction. Arch Dermatol. 1974;110(2):238-242. doi:10.1001/archderm.1974.01630080040010