The reliability and validity of a short food frequency questionnaire among 9–11-year olds: a multinational study on three middle-income and high-income countries

Abstract

OBJECTIVE:The main aim of this study was to assess the reliability and validity of a food frequency questionnaire with 23 food groups (I-FFQ) among a sample of 9-11-year-old children from three different countries that differ on economical development and income distribution, and to assess differences between country sites. Furthermore, we assessed factors associated with I-FFQ's performance. METHODS: This was an ancillary study of the International Study of Childhood Obesity, Lifestyle and the Environment. Reliability (n = 321) and validity (n = 282) components of this study had the same participants. Participation rates were 95% and 70%, respectively. Participants completed two I-FFQs with a mean interval of 4.9 weeks to assess reliability. A 3-day pre-coded food diary (PFD) was used as the reference method in the validity analyses. Wilcoxon signed-rank tests, intraclass correlation coefficients and cross-classifications were used to assess the reliability of I-FFQ. Spearman correlation coefficients, percentage difference and crossclassifications were used to assess the validity of I-FFQ. A logistic regression model was used to assess the relation of selected variables with the estimate of validity. Analyses based on information in the PFDs were performed to assess how participants interpreted food groups. RESULTS: Reliability correlation coefficients ranged from 0.37 to 0.78 and gross misclassification for all food groups was o5%. Validity correlation coefficients were below 0.5 for 22/23 food groups, and they differed among country sites. For validity, gross misclassification was o 5% for 22/23 food groups. Over-or underestimation did not appear for 19/23 food groups. Logistic regression showed that country of participation and parental education were associated (P ⩽ 0.05) with the validity of I-FFQ.

Association between home and school food environments and dietary patterns among 9–11-year-old children in 12 countries

“…In addition, the food items listed in the two questionnaires were not identical. However, in the validation study of the ISCOLE FFQ, 19 some misreporting of food intake based on social desirability was observed; the consumption frequency of three food groups representing recommended, healthy foods was slightly overestimated, whereas the food group 'cakes and so on' was underestimated. We used previously identified dietary patterns and scores representing the overall quality of diet as the outcome variables.…”

“…Detailed information on the dietary assessment methods and the identification of dietary patterns can be found elsewhere. 15,19 In brief, for each site we chose two components, which were rotated with an orthogonal varimax transformation to enhance the interpretation, and based on food group loadings labeled them as 'unhealthy diet pattern' (characterized by high intakes of, for example, fast foods, ice cream, fried food, French fries and potato chips) and 'healthy diet pattern' (including, for example, dark-green vegetables, orange vegetables, vegetables in general and fruits and berries). In the present paper, we use standardized principal component scores for these two patterns as the dependent variables (unhealthy and healthy diet pattern scores).…”

“…19 Items in the FFQ used were not identical with the food availability questionnaire used to assess home food environment. To identify existing dietary patterns, we carried out principal components analysis using the FFQ food groups as input variables.…”

An international comparison of dietary patterns in 9–11-year-old children

“…The main objective of the substudy was to assess the reliability and validity of the FFQ applied in ISCOLE. 16 …”

“…Fruit juices were excluded from these analyses owing to low validity. 16 The PCAs were performed first by using the total data set, and then for each site separately. The scree plot curve showed a decline with a clear elbow between the second and third components, thus two components were eventually chosen for each analysis.…”