title: Reliability and relative validity of an FFQ for nutrients in the Tehran lipid and glucose study.
abstract: OBJECTIVE
  To describe the relative validity and reliability of the FFQ used for assessing nutrient intakes of participants in the Tehran Lipid and Glucose Study (TLGS).
  
  
  METHODS
  A total of 132 subjects (sixty-one males and seventy-one females) were included in the study. Dietary data were collected monthly by means of twelve 24 h dietary recalls (24hDR). Subjects completed two, 168-item semi-quantitative FFQ. Blood and urine samples were taken every season for measurement of plasma biomarkers and urinary N and K.
  
  
  RESULTS
  Mean age and BMI of the participants were 35.5 (sd 16.8) years and 25.5 (sd 5.2) kg/m2, respectively. The mean energy-adjusted and deattenuated correlation coefficients for overall nutrient intake between the 24hDR and FFQ2 were 0.44 and 0.37 in <or=35-year-olds and >35-year-olds, respectively, and for individual nutrients ranged from 0.24 to 0.71 in men (mean r = 0.53) and from 0.11 to 0.60 in women (mean r = 0.39). The mean energy-adjusted reliability coefficients varied from 0.48 in <or=35-year-olds to 0.65 in >35-year-olds, and ranged from 0.41 to 0.79 in men (mean r = 0.59) and from 0.39 to 0.74 in women (mean r = 0.60). The FFQ2 and 24hDR produced exact agreement rates ranging between 39.6 % and 68.3 % in men and between 39.6 % and 54.1 % in women. The ranges of questionnaire validity coefficients, with the sample correlation between the questionnaires and biochemical marker as the lower limit and the estimate obtained by the method of triads as the upper limit, were 0.21-0.56 (protein) and 0.37-0.61 (K).
  
  
  CONCLUSIONS
  The FFQ developed for the TLGS has reasonable relative validity and reliability for nutrient intakes in Tehranian adults.
authors.affiliation: 1Obesity Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, PO Box 19395-4763, Tehran, Islamic Republic of Iran.
authors.forename: Parvin
authors.initials: P
authors.lastname: Mirmiran
authors.forename: Firoozeh Hosseini
authors.initials: FH
authors.lastname: Esfahani
authors.forename: Yadollah
authors.initials: Y
authors.lastname: Mehrabi
authors.forename: Mahdi
authors.initials: M
authors.lastname: Hedayati
authors.forename: Fereidoon
authors.initials: F
authors.lastname: Azizi
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000517:prevention & control; D004034:Diet Surveys; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007492:Iran; D008297:Male; D011939:Mental Recall; D024821:Metabolic Syndrome / Q000453:epidemiology / Q000517:prevention & control; D009584:Nitrogen / Q000652:urine*; D011188:Potassium / Q000652:urine*; D015203:Reproducibility of Results; D012307:Risk Factors; D012621:Seasons; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*
chemical_list: D015415:Biomarkers; D009584:Nitrogen; D011188:Potassium