VALIDATION OF A FOOD FREQUENCY QUESTIONNAIRE FOR ASSESSING DIETARY-INTAKE IN A STUDY OF CORONARY HEART-DISEASE RISK-FACTORS IN CHILDREN

A food frequency questionnaire (FFQ) was designed and validated for us e in an epidemiological survey measuring coronary heart disease risk f actors in British children. The questionnaire asked about the frequenc y of children's consumption of 35 food items over the previous month a nd was completed by parents/guardians. Food items represented a range of food groups from which children may eat, with emphasis on foods wit h a high fat and fibre content. The questionnaire was validated agains t 14 daily recalls of consumption, using the same food list as the FFQ . The sample consisted of 272 children, aged 5-11 years, The response rate for the FFQ was 92% and for the recall, 82% in the first week and 66% in the second week. The level of agreement between the FFQ and th e recall was measured by calculating (McGinnis JM & Nestle M, 1989, Am . J. Clin. Nutr. 49, 23-28) the median difference between results from the two methods and (Willett WC (ed.), 1990, Nutritional epidemiology , ch. 15; Oxford University Press) the percentage of children classifi ed by FFQ to within +/- 1 day per week of the recall. Median differenc es between individual items on the questionnaire and the recall were l ess-than-or-equal-to 0.5 days for 91% of items and equal to 1 day for the remainder. The percentage agreement to within +/- 1 day per week b etween frequencies reported in the two methods ranged from 99.8% for l amb to 46.8% for low-fibre cereal. Better agreement was found for food items representative of fat intake than those of fibre intake. Childr en were also scored according to their frequency of intake of fat (hig h/low) and fibre (high/low) to develop 'nutrient intake profiles'. The agreement between the profile scores derived from the FFQ and the rec all were assessed by weighted kappa statistics. Moderate agreement was achieved for the profiles of high fat, low fat and low fibre (kappa(w t) = 0.58, 0.71 and 0.59, respectively) but lower for high fibre (kapp a(wt) = 0.48). The questionnaire proved a valid instrument for classif ying children into broad patterns of consumption in an epidemiological study assessing children's risk factors for coronary heart disease an d for following trends in children's dietary intake over time.