AN ASSESSMENT, AND REPRODUCIBILITY OF FOOD FREQUENCY DATA PROVIDED BYHOSPITAL CONTROLS

In order to assess the comparability and reproducibility of informatio n from a questionnaire used in a case-control study on digestive tract cancers conducted in Italy, a total of 400 subjects were randomly sel ected from a large sample of hospital controls and contacted at home t o repeat the interview. Of these, 294 (73%) subjects were re-interview ed. Mean values of intake were computed for the 400 subjects selected, and among the 294 responders for the first and second interview. Thes e values were comparable, most of them being within a 10% range. Spear man correlation coefficient (r(s)) values of consumption between the f irst and second interview were > 0.65 for consumption of pastries, pas ta or rice, bread, fish, milk, green vegetables, eggs and apples; betw een 0.50 and 0.65 for meat, chicken, liver, ham, cold cuts, cheese, fr uit, cabbage, carrots, tomatoes, peppers, salad, citrus fruit and melo n; and lower than 0.50 for a few infrequently eaten foods. For all foo ds, the estimated average weekly intake in the second interview increa sed consistently and substantially with increasing tertile of the firs t interview. This study shows a satisfactory comparability of dietary information from subjects interviewed at home with that provided durin g their original interview in the hospital, and a good reproducibility of information collected in the two settings.