Validation and reproducibility of a semi-qualitative food frequency questionnaire for assessment of sodium intake in Iranian population

Abstract Background Few semi-quantitative food frequency questionnaire (SFFQ) has yet been developed to assess sodium intake s in Middle East region. This study was performed to validate SFFQ for sodium consumption assessment and evaluation of food groups΄ contribution in sodium intake.Methods This was a validation study. This study was performed on 198 healthy participants aged ≥ 6 years in Isfahan city, central part of Iran in 2014–2015. They provided two SFFQ at the beginning and after one year to evaluate the reproducibility. The validity of SFFQ for assessment of sodium intake compared with 24-hour urine sodium and twelve 24-hour dietary recalls which were completed monthly during a year as two standard methods.Results Correlation coefficient between the contribution of food groups to sodium intake based on SFFQ and 24-hour dietary recalls varied from 0.04 for legumes (P = 0.667) to 0.47 for added salt (P < 0.001). There was a significant correlation between the estimated total sodium intake based on SFFQ and both standard methods (P < 0.01). Intraclass correlation coefficient (95% CI) between first and second SFFQ had a diverse range from 0.10 (0.05–0.17) for fats and oils to 0.49 (0.28–0.69) for bread. According to the Bland-Altman plots, we observed an acceptable level of agreement between the two methods for sodium intake.Conclusions The SFFQ was a relatively valid and reliable method for estimating sodium intake and food groups contribution in its intake. A combination of two or more methods will be useful in achieving more accurate results.