title: [Study of validity and reproducibility of food frequency questionnaires for residents over 50-years-old in Xi'an City].
abstract: OBJECTIVE
  To examine the validity and reproducibility of Xi'an food-frequency questionnaire (FFQ) used to evaluate the diet intakes for residents in Xi'an City.
  
  
  METHODS
  125 males and females aged 50-80 years, from districts of urban Xi'an City, participated and completed all the six interviews in this study. Reproducibility of the questionnaire measurements was obtained by a repeated administration of the FFQ at one year interval. The mean of 24-hour dietary recalls (24-HDR) applied at three months intervals served as reference method for the estimation of the relative validity of questionnaire measurements.
  
  
  RESULTS
  Spearman correlation coefficients for reproducibility between two FFQs ranged from 0.38 for cakes to 0.74 for tea. Coefficients for validity assessed by four 24-HDRs were statistically significant for almost all food groups ranged from 0.12 to 0.74. After correction for within-subjects error, all correlation coefficients were improved, ranged from 0.17 to 0.79.
  
  
  CONCLUSIONS
  Therefore, Xi'an FFQ appears to be reasonably valid and reliable for most food groups.
authors: School of Medicine, Xi'an Jiaotong University, Xi'an 710061, China. wangxiaoqin@mail.xjtu.edu.cn
authors: Xiaoqin
authors: X
authors: Wang
authors: Hong
authors: H
authors: Yan
authors: Rina
authors: R
authors: Sa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002681:China; D002947:Cities; D004034:Diet Surveys; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D009752:Nutritional Status; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*