ASSESSMENT OF THE VALIDITY OF A FOOD FREQUENCY QUESTIONNAIRE AS A MEASURE OF FOOD USE BY COMPARISON WITH DIRECT OBSERVATION OF DOMESTIC FOOD STORES

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Abstract
The aim of this study was to assess the validity as a measure of food use of a 90-item semi-quantitative food frequency questionnaire which had been used in a study of food consumption patterns and health among 3,000 people aged 65 years and over selected at random from the electoral rolls of Adelaide, South Australia. In 1986, 18 months after the original survey, 200 randomly selected participants were invited to take part in the present study. The food frequency questionnaire was administered by mail, and results were compared with a direct observation of the foods that 40 subjects had in their home. The kappa statistic indicated good agreement (in all cases greater than that expected due to chance) between the reported use of individual foods in the questionnaire and the observed presence or absence of those foods in the subject's home. Correlation coefficients between scores generated from the questionnaire for consumption from specific food groups and those derived from direct observation of domestic food stores ranged from 0.42 to 0.86. These data indicate that a simple self-administered dietary questionnaire can provide a valid measure of food use patterns in elderly people.