Relative validity and reproducibility of the CyFFQ semiquantitative food frequency questionnaire for assessing dietary intake in Cypriot adults

Background Assessment of dietary intake is fundamental for evaluating the interrelationships between diet and disease. The present study aimed to develop and validate the semiquantitative Cypriot food frequency questionnaire (CyFFQ). Methods A 171-item paper-and-pencil semiquantitative interview-administered FFQ was developed, including local foods and culturally specific meals commonly consumed among Cypriot adults. FFQ reproducibility was assessed by comparing the energy-adjusted daily macro- and micronutrients intake at baseline (FFQ1) and 1 year later (FFQ2) using a Wilcoxon matched pairs signed rank test and intraclass correlation coefficients (ICCs) in a random sample of Cypriot adults. FFQ relative validity was evaluated by comparing the intake as estimated by FFQ2 with that obtained from the average of three 24-h recalls taken over the year between FFQ1 and FFQ2. Associations between nutrient intakes estimated using FFQ2 and the 24-h recalls were assessed using Spearman rank correlation and Bland-Altman plots were used to assess agreement between the FFQ and the 24-h recalls. Results Among eligible participants, 68 (78%) completed the study (44.1% males, aged 30.5-47.5 years). The energy-adjusted intakes of macro- and micronutrients did not significantly differ between the two FFQs, excluding magnesium. The FFQ2 and the averaged 24-h recalls were significantly correlated for most macro- and micronutrients. The median (interquartile) ICC for all macro- and micronutrients was 0.46 (0.38-0.52) (p < 0.05). Agreement was satisfactory (>30%) for most micro- and macronutrients. Bland-Altman plots also confirmed good agreement between the two methods. Conclusions The CyFFQ is a valid and reliable tool for assessing dietary consumption in Cypriot adults.