Abstract
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. 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. Forty-three women, aged 19-49years, took part in the validation of the 17-items FFQ. Median (interquartile range) UIC was 74(47-92) μgL(-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 μgL(-1) (rs =0.34, P=0.025) but not in μgday(-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. The FFQ provides a rapid and reliable estimate of dietary iodine exposure to identify those population subgroups at risk of iodine deficiency.
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