Examining the relative validity of an adult food frequency questionnaire in children and adolescents

Background And Objective: Dietary factors have been implicated in the pathogenesis of inflammatory bowel diseases (IBD). The aim of the study was to assess the accuracy of a food frequency questionnaire (FFQ) developed in French and English for adults 18 years and older, among subjects ages 7 to 18 years participating in a prospective cohort study. PATIENTS AND Methods: Healthy children and adolescents ages 7 to 18 years were recruited from outpatient orthopedic clinics in a Montréal pediatric hospital. Of the 131 recruits, 65 (86% Francophone) provided a complete 78-item semiquantitative FFQ and 3-day nonconsecutive food records (3D-FR). Parents of young children completed both instruments, whereas older children and adolescents completed them on their own. The FFQ were analyzed using Microsoft Access software for customized data entry and the 3D-FR were analyzed using CANDAT software, both based on the 2007b Canadian Nutrient File. Results: The FFQ overestimated intakes relative to the 3D-FR by around 15%. Spearman rank correlation coefficients between test and reference methods were positive, largely ranged from 0.22 (vitamin C) to 0.57 (saturated fat), and were generally statistically significant (0.05< P < 0.0001). Stronger associations between test and reference methods were found for adolescents (13-18 years) and for girls. Some 77% of participants were jointly classified into the same half of the distribution, with 39% exact agreement and only 6% frank misclassification. Conclusions: The FFQ can be confidently used to rank young subjects on a range of nutrient intakes with the potential to provide useful information on dietary risk factors in the etiology of inflammatory bowel disease. Accuracy could be enhanced by improving completion quality of FFQs, notably by young adolescent boys.