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Table 3 Spearman’s rho correlation coefficient a between estimated iodine intake from I-FFQ (μg/day), estimated iodine intake from food diary (μg/day) and urinary iodine concentration (UIC) (μg/L)

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

Iodine intake from I-FFQb vs. Food diaryc (n = 123) I-FFQb vs. UICd (n = 123) Food diaryc vs. UICd (n = 134)
Diet 0.36 (P < 0.001) 0.06 (P = 0.488) 0.18 (P = 0.042)
Diet and supplements 0.62 (P < 0.001) 0.21 (P = 0.018) 0.41 (P < 0.001)
  1. aSpearman’s rank order correlation coefficient. The correlation coefficients strength (effect size) was considered poor if < 0.20, acceptable if 0.20–0.49 and strong if ≥0.50 in according to previously used dietary methods [30]
  2. bIodine specific food frequency questionnaire (I-FFQ)
  3. cIodine specific food diary from six consecutive days
  4. d Urinary iodine concentration (UIC): Pooled sample of spot urinary samples from six consecutive days