Aim: To validate a semi-quantitative food frequency questionnaire (SFFQ) and assess the dietary intake of Iranian adults.
Methods: This study was conducted among 113 healthy adults in Iran. We administered twelve 24-hour dietary recalls (24DRs) during a year as a reference method. The 165-item SFFQ was administered twice, along with the first and last 24DRs. To examine validity and reproducibility of SFFQ, the correlation coefficients (r) and de-attenuated correlation coefficients and intra-class correlation coefficient (ICC) between 24DRs and SFFQ were calculated. The Bland-Altman method was used to assess agreement between the two methods.
Results: De-attenuated correlations varied from 0.42 (polyunsaturated fatty acids) to 0.62 (energy) (all P < .001) for nutrients and from 0.48 (oils and fats) to 0.65 (sweets) for food groups (all P < .05). We found reasonable reproducibility of SFFQ for both nutrients and food groups. ICC (95%CI) varied from 0.47 (0.15-0.74) for saturated fatty acids to 0.64 (0.47-0.76) for energy and from 0.43 (0.15-0.62) for oils and fats to 0.58 for grains (0.31-0.69). According to the Bland-Altman plots, we observed an acceptable level of agreement between the two methods.
Conclusions: We found reasonable relative validity and acceptable reproducibility of SFFQ. This SFFQ can be used to classify individuals based on their dietary intake in our population.
Keywords: diet; food frequency questionnaire; reliability; reproducibility; validity.
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