Correlation of the Vasoconstrictor Assay and Clinical Activity in Psoriasis

To the Editor.— I read with great interest the article by Cornell and Stoughton 1 about the correlation between the vasoconstrictor activity and clinical efficacy of topical corticosteroids. I also have been involved in this area of research and have come to similar conclusions, 2 although the vasoconstrictor assay technique and the timing of readings employed by myself and my colleagues were different. We achieved the best correlation with clinical efficacy in psoriasis when we used the occluded vasoconstrictor assay with removal of materials at six hours followed by serial readings between seven and 25 hours and analysis of the area-under-the-curve values thus obtained. This assay also produced a useful general profile of the corticosteroid's vasoconstrictor activity. I would agree that a single reading often gives valuable information, but this approach can occasionally be misleading, as in the case of 0.05% clobetasone butyrate ointment (Eumovate), whose vasoconstrictor activity is potent