Reliability and validity of a semi-quantitative food frequency questionnaire: dietary intake assessment among multi-ethnic populations in Northwest China

BACKGROUND: Few multi-ethnic dietary culture-sensitive food frequency questionnaires (FFQ) have been developed due to the complexity and diversity of cooking methods and styles. This study aimed to develop and validate a specific FFQ among multi-ethnic groups in Northwest China. METHODS: In the reliability study, 139 participants aged 20–65 completed two identical FFQs separated by 3 months. The relative validation of the FFQ was assessed by three 24-h recalls (24HR) employed in the interval of two FFQs, as a reference. Stratified analyses were also conducted by the major ethnic groups (Han nationality or Ethnic minority). RESULTS: For reproducibility, the median (range) of Spearman’s correlation coefficients (SCC) was 0.71 (0.43–0.84) for nutrients. The intra-class correlation coefficients (ICC) covered a spectrum from 0.39 to 0.78 (median: 0.64). Meanwhile, the weighted kappa values ranged from 0.11 to 0.64. For validity, the median (range) of Pearson’s correlation coefficients derived from the energy unadjusted and the adjusted values between FFQ and 24HR were 0.61 (0.12–0.79) and 0.56 (0.12–0.77), respectively. The results of correlation coefficients were similar between the two ethnic groups. Moreover, the Bland–Altman plots likewise demonstrated a satisfactory level of agreement between the two methods. CONCLUSIONS: The FFQ showed acceptable reproducibility and moderate relative validity for evaluating dietary intake among multi-ethnic groups in northwest China. It could be a credible nutritional screening tool for forthcoming epidemiological surveys of these populations. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s41043-023-00452-9.