Reply
Authors: Chérie M. Ditre, Thomas D. Griffin, George F. Murphy, Hirohiko Sueki, Brett TelegancWaine C. Johnson, Ruey J. Yu, Eugene J. Van Scott
Journal: Journal of the American Academy of Dermatology (1997)

We thank Dr. Whitmore for her interest and comments on our pilot study of the effects of α-hydroxy acids (AHAs) on photoaged skin. In reporting our results, we, like many other investigators, have no control over the misuse of scientific data for commercial gain. The 25% concentration of the AHAs was purposely chosen to avoid any endorsement of a commercially manufactured product because this formulation is not available. However, we respectfully disagree with her statement that the claim of increased papillary dermal collagen density, acid mucopolysaccharide content, and improved elastic fiber quality was not substantiated by our results. As we stated in the article on page 193, the increased papillary dermal collagen density of the AHA-treated sites was greater than that of the control sites as measured by quantitative image analysis, but the difference was not statistically significant. With regard to the acid mucopolysaccharide content, we state that the three independent dermatopathologists judged the staining to be variably increased in the papillary dermis in the AHA-treated specimens. This variation correlated with the clinical observation of variable increases in skin forearm thickness (thickness measurements outlined per patient in Table I, page 189). We showed that the improved elastic fiber quality was defined by their appearance as less fragmented and wavy fibers on Verhoeff van Gieson staining. The morphology of photodamaged elastic fibers has been documented in the past by other investigators and has been characterized as short and fragmented. This contrasts with the appearance of normal or nonphotodamaged elastic fibers as long, wavy, and nonfragmented. Dr. Whitmore expressed her confusion over the selection of eight of the 17 subjects in the study. Although all 17 subjects were asked to donate a specimen for evaluation, only eight consented. There was no bias made to their response to treatment. All three dermatopathologists were masked as to the type of AHA treatment applied to the subject's skin as well as to which side received the AHA treatment. They were also unaware of the patients' identities and their clinical responses. Therefore no bias could be attributed to the dermatopathologists' results. Incorrectly, Dr. Whitmore notes that the statistical testing was only applied to the dermal collagen density data. As shown in the "Results" section on page 191, the clinical findings of increased forearm skin thickness measurements were statistically analyzed and revealed a 25% increase in the AHA-treated sites that was found to be statistically significant ( p < 0.0001). In addition, the mean epidermal and papillary dermal thickness, as measured by histologic quantitative image analysis, were both found to be significantly increased after AHA treatment ( p = 0.0001 and p = 0.042, respectively [page 192]). With regard to the question of a paired Student t test, we regret that a typographic error was not detected on page 187 in the "Material and Methods" section; this was a paired t test, not a "partial" t test as printed. However, we again respectfully disagree with Dr. Whitmore because this type of test is acceptable in analyzing these data. We refer Dr. Whitmore to Bolton's text on pharmaceutical statistics. 1Bolton S. Pharmaceutical statistics: practical and clinical applications.in: 2nd ed. Marcel Dekker, New York1990: 494Google Scholar In this text he cites that the typical parametric methods (i.e., t tests) are commonly applied to rating such data as we presented and are accepted by many statisticians, including members of the Food and Drug Administration. We agree with Dr. Whitmore that the t test did not show a statistically significant increase in papillary dermal collagen as stated on page 193. We regret our oversight in not including this finding in the abstract. Finally, we stress that this was a pilot study and an attempt to obtain scientific data regarding the effects of AHAs on the skin's epidermal and dermal compartments. To date, we are not aware of any other published collaborative exploratory effort.