title: Validation of a short food frequency questionnaire specific for iodine in U.K. females of childbearing age.
abstract: BACKGROUND
  Widespread subclinical iodine insufficiency has recently been reported in Europe, based on urinary iodine using World Health Organization/Food and Agriculture Organization criteria, in particular among young women. Although urinary iodine concentration (UIC) is a useful measurement of the iodine status in a population, it does not provide an insight into the habitual iodine intake of this population. This is compounded by the fact that very few iodine-specific food frequency questionnaires (FFQ) have been validated so far. The present study aimed to develop and validate a new, simple, rapid survey tool to assess dietary iodine exposure in females of childbearing age.
  
  
  METHODS
  Iodine was measured in a duplicate 24-h urine collection. Iodine intake was measured with duplicate 4-day semi-quantitative food diaries and the FFQ. Correlation, cross-classification and Bland-Altman analyses were used to estimate agreement, bias and the reliability of the method. The triangular (triad) method was used to calculate validity coefficients.
  
  
  RESULTS
  Forty-three women, aged 19-49 years, took part in the validation of the 17-items FFQ. Median (interquartile range) UIC was 74 (47-92) μg L(-1) , which is indicative of mild iodine insufficiency. The FFQ showed good agreement with food diaries with respect to classifying iodine intake (82% of subjects were classified in the same or adjacent quartile). The FFQ was moderately correlated with the food diaries (rs  = 0.45, P = 0.002) and urinary excretion in μg L(-1) (rs  = 0.34, P = 0.025) but not in μg day(-1) (P = 0.316). The validity coefficients were 0.69, 0.66 and 0.52 for the food diaries, FFQ and urinary iodine excretion, respectively.
  
  
  CONCLUSIONS
  The FFQ provides a rapid and reliable estimate of dietary iodine exposure to identify those population subgroups at risk of iodine deficiency.
authors.affiliation: Human Nutrition, School of Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow Royal Infirmary, Glasgow, UK.
authors.forename: E
authors.initials: E
authors.lastname: Combet
authors.forename: M E J
authors.initials: ME
authors.lastname: Lean
mesh_terms: D000328:Adult; D003677:Deficiency Diseases / Q000453:epidemiology / Q000209:etiology; D004032:Diet; D015930:Diet Records; D004034:Diet Surveys / Q000592:standards*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D007455:Iodine / Q000008:administration & dosage* / Q000172:deficiency / Q000652:urine; D008875:Middle Aged; D015596:Nutrition Assessment; D015203:Reproducibility of Results; D012307:Risk Factors; D011795:Surveys and Questionnaires / Q000592:standards*; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007455:Iodine
keywords: childbearing age; females; food frequency questionnaire; iodine; triads method; validation