Advantages of collecting multiple urinary iodine concentrations when assessing iodine status of a population.

Aim: To evaluate the effect of collecting multiple (four) urine samples on the extensive variance often observed within a cohort when determining iodine status via urinary iodine concentration (UIC).

Methods: Fifty-one children aged two to three years and thirty children aged 8-10 years participated in the study in South East Queensland, Australia. Each child's four urine samples were analysed using ammonium persulphate digestion before a Sandell-Kolthoff reaction method. Analysis of variance techniques were used to assess the effect of using multiple urine samples.

Results: The median UICs were 223.3 and 141 μg/L for two- to three-year-olds and eight- to 10-year-olds, respectively. The coefficient of variance (CV) of UIC for children aged two to three years was reduced by 35.6%, 36.5% and 39.7% when two, three and four samples were included in the adjustment, respectively. Similarly, the CV of UIC for children aged 8-10 years was reduced by 24.7%, 30.7% and 34.7%, respectively.

Conclusion: Although the practicality and cost of collecting multiple UICs need to be considered, collecting multiple UIC samples from each participant provides a more accurate reflection of a cohort iodine status.