To the Editor.—
"Epidemiology" is the study of disease in populations. "Clinical" studies, on the other hand, focus on patients rather than on populations.1 Failure to appreciate this distinction leads to misconceptions about the meaning of medical data, and too often leads to fallacious conclusions concerning the frequency and cause of pathologic conditions.2(pp284-285) Two articles in a recent issue of the Archives (108:517, 537, 1973) illustrate this point.The article by Dajani et al titled "Endemic Superficial Pyoderma in Children" describes a well-performed epidemiologic study. The observations provide a measure of the frequency of pyoderma in defined populations of children at given points of time. (This kind of measure is properly referred to as the prevalence, and is expressed in percent.) Comparisons of rates of pyoderma are made between appropriately controlled age and sex groups to determine whether these factors influence the risk of contracting the disease.In
Allen AM. Use and Misuse of "Epidemiology". Arch Dermatol. 1974;110(1):131–132. doi:10.1001/archderm.1974.01630070089033
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