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

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)

Iodine intake from	I-FFQ^b vs. Food diary^c (n = 123)	I-FFQ^b vs. UIC^d (n = 123)	Food diary^c vs. UIC^d (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)

^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]
^bIodine specific food frequency questionnaire (I-FFQ)
^cIodine specific food diary from six consecutive days
^d Urinary iodine concentration (UIC): Pooled sample of spot urinary samples from six consecutive days

ISSN: 1475-2891