Frequency factor, definition significance

Atopic diathesis is indubitably a common human trait, but several factors make it difficult to obtain an absolutely accurate measurement of its true frequency (1) differences in definition of the state and of individual diseases that accompany it (2) significant influences of race, sex, and environmental factors in the production of clinical disease (3) the natural history of the individual conditions, with remissions and exacerbations, means that prevalence figures at any given time underestimate the number of patients actually at risk and (4) symptoms occurring in early life are often not recognized as atopic. However, one can estimate that at least one in five Western individuals will have experienced at least one atopic disorder by the age of twenty. The frequency of positive skin tests, with or without symptoms, indicates that about a third of the population carry the atopic predisposition (Davis, 1976 Godfrey and Griffiths, 1976). 

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