RELATIVE VALIDITY AND REPRODUCIBILITY OF A FOOD FREQUENCY DIETARY QUESTIONNAIRE FOR USE IN THE ITALIAN EPIC CENTERS

A pilot questionnaire was developed for the EPIC centres of northern I taly, and validated in the feasibility part of the cohort project. The questionnaire was self-administered and of the food frequency type wi th portion size estimated by means of pictures. It was structured by c ourses within a meal characteristic of Italian dietary habits. Dietary intake estimated by the questionnaire was compared to the correspondi ng estimates obtained from 8-14 24-hour recall interviews administered over a 1-year period, The reference method was validated by means of urinary nitrogen in 4-6 repeated 24-hour urine collections. One hundre d and ninety-seven volunteers (47 men and 150 women) were enrolled and completed the study lasting 1 year. They filled out two questionnaire s at the beginning and at the end of the study, and had a 24-hour reca ll interview once a month. Twenty-four-hour urine samples were collect ed at regular intervals. Usual intake of energy, the major nutrients a nd some vitamins were estimated for the questionnaires and the referen ce method by means of food composition tables compiled for this study. The agreement between the questionnaire and the 24-hour recalls was o nly good for alcohol consumption: Pearson's correlation was 0.73 and 0 .77 in men and women respectively. Otherwise the relative validity of the questionnaire ranged between 0.28 for fat to 0.52. for carbohydrat es in men and 0.25 and 0.50 in women for the same nutrients. The valid ity of the two interview methods in estimating protein intake, compare d to mean urinary nitrogen was 0.24 (M) and 0.18 (W) for the questionn aire and 0.63 (M) and 0.48 (W) for 24-hour recalls. The main causes of low performance of the questionnaire were identified to be the estima ted intake of dressing and cooking rats, Vegetables and meat. Remedies were devised and introduced in the final version of the questionnaire currently in use in the EPIC project.