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Table 4 Agreement of quartile membership between estimated iodine intake from the iodine-specific food frequency questionnaire (I-FFQ) and the food diary, and urinary iodine concentration (UIC)

From: Validation and reproducibility of a new iodine specific food frequency questionnaire for assessing iodine intake in Norwegian pregnant women

  I-FFQa vs. Food diaryb (n = 122) I-FFQa vs. UICc (n = 123) Food diaryb vs. UICc (n = 133)
Stable quartile, n (%) 57 (47%) 41 (33%) 53 (40%)
Adjacent quartile, n (%) 51 (42%) 51 (42%) 50 (38%)
Opposite quartile, n (%) 14 (11%) 31 (25%) 30 (23%)
Weighted kappa, kw d 0.60 0.21 0.40
  1. aIodine specific food frequency questionnaire (I-FFQ)
  2. bIodine specific food diary from six consecutive days
  3. cUrinary iodine concentration (UIC): Pooled sample of spot urinary samples from six consecutive days
  4. dTracking coefficient of Cohen’s weighted kappa. A kw of 0.01–0.20 represents slight agreement, 0.21–0.40 fair agreement, 0.41–0.60 moderate agreement, 0.61–0.80 substantial agreement, and 0.81–1.00 almost perfect agreement [33]