To the Editor.—
We were disappointed to note that the recent study by Halprin et al1 on the effect of flurandrenolone occlusive tape on enzymes of psoriatic skin apparently provides little insight into the treatment rationale. We believe that much of the negative tenor of this report is due to improper experimental design and to incomplete analysis of the data, as the following comments will show.Halprin and co-workers express enzyme activities on the basis of wet weight of tissue, in contrast to the conventional use of dry-tissue weight. In a different study,2 Halprin and Ohkawara considered that dry weight offered no advantage over wet weight because normal, psoriatic, and treated skin were observed to contain about the same amount of water. But surely hydration occurs under occlusive tape—with the inevitable consequence that any parameter (except water content!) based on wet weight of tissue will be reduced. It