Development and validation of an iodine-specific FFQ to estimate iodine intake in Australian pregnant women.

The British journal of nutrition
Q1
Mar 2015
Citations:35
Influential Citations:5
Observational Studies (Human)
83
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Enhanced Details

Methods
Observational validation study of an iodine-specific FFQ (I-FFQ) in pregnant Australian women. 122 participants aged 18–41, enrolled before 20 weeks gestation; 96 completed. Nested in the PINK cohort; ethics approval obtained.
Results
I-FFQ shows moderate validity for iodine intake from food (r = 0.349, P < 0.001) and very strong validity when iodine supplements are included (r = 0.876, P < 0.001). Adequacy classification agreement improves from 66% (food alone) to 90% (food plus supplements) with kappa rising from 0.28 to 0.72. Reproducibility across pregnancy is strong (r = 0.622). Total iodine intake estimated by I-FFQ correlates with 24 h UIE and 24 h UIC, but not with spot UIC. Supplement users show moderate correlations with UIE/UIC; non-supplement users show weaker or no correlation. Iodised salt use raises UIE but does not consistently affect UIC. No association with thyroid function markers (TSH, fT3, fT4, Tg) after adjustment. Conclusion: The I-FFQ is a valid, reproducible tool to screen for inadequate iodine intake in pregnant Australian women, with limited ability to predict thyroid function; could be refined to quantify iodised salt or adapted to similar populations.
Limitations
Small, single-country sample; observational validation; iodine intake from iodised salt not quantified; only one 24 h urine and one spot urine sample; PABA not used to check collection completeness; thyroperoxidase not measured; Tg antibodies measured but autoimmunity not fully excluded; results may not generalize beyond Australian pregnant population; majority used iodine supplements; self-reporting biases in FFQ; potential measurement error; inability to quantify salt iodine intake may weaken associations.

Abstract

Adequate iodine is important during pregnancy to ensure optimal growth and development of the offspring. We validated an iodine-specific FFQ (I-FFQ) for use in Australian pregnant women. A forty-four-item I-FFQ was developed to assess iodine intake f...