Reproducibility and validity of a food-frequency questionnaire (NFFQ) to assess food consumption based on the NOVA classification in adults

NOVA is a classification that divides foods into four groups according to processing. Since no questionnaires have been validated to assess the consumption of foods with different levels of processing in the general adult population, we tested the reliability and validity of a 94-item Food Frequency Questionnaire (NFFQ) designed to estimate the intake (g/day) and the weight ratio (%) of the NOVA food groups in Italian adults. Time reliability and validity were tested by administrating the NFFQ to 110 subjects on two different occasions and comparing it with a weighed dietary record (WDR). Strong correlations between NFFQs (r>0.7, p<0.001) and intraclass correlation coefficients (ICC) of 0.851-0.940 indicated good test-retest reliability. Moderate correlations between the NFFQ and the WDR (0.6<0.7), ICC of 0.536-0.741, and consistent agreement for intake percentages as revealed by Bland-Altman plots indicated moderate to good validity. The NFFQ could be useful for future investigations in this research field.