Questionnaire based exposure assessment methods.

In environmental epidemiological studies, questionnaires may be the method of choice for assessing exposure because no other source of information is available, or because they provide the most efficient study design, allowing a larger study size and greater statistical power than would be possible with other more accurate measurement techniques. Problems may arise from a lack of content validity (the questionnaire does not cover all sources of exposure to the hazard of interest) or criterion validity (e.g., through inaccurate recall or misunderstanding of questions). Methods for validating questionnaires are described. The usefulness of validated 'standard' questionnaires is discussed, particularly in regard to comparison of exposure patterns in various populations studied separately. It is stressed that the validity of standard questionnaires should not be automatically assumed when they are applied to populations other than those in which they have been tested.