Assessing the risk of iodine deficiency – a study to validate a digital screening tool in UK adults

Iodine is essential for thyroid hormone synthesis and is needed for brain development. In the UK, milk and dairy products are the main dietary sources, but the increasing consumption of plant-based alternatives may affect iodine intake. Few iodine-specific dietary assessment tools have been validated in UK adults, and none reflects recent changes in food availability, food composition and dietary patterns. This study aimed to develop and validate the Iodine Intake Risk Score screening tool, using a rapid digital iodine-specific questionnaire. Healthy UK adults (n 108) aged ≥18 years completed the Iodine Intake Risk Score screening tool and a 6-d food diary, which served as the reference method. Iodine intake from the tool and food diaries was estimated and was classified as insufficient (<140 µg/d) or sufficient (140-600 µg/d). Agreement between methods was assessed using Cohen's kappa, Wilcoxon signed-rank tests and Spearman's correlation. There was substantial agreement in iodine classification (κ = 0·68, p < 0·001). The screening tool demonstrated high sensitivity (82%) and specificity (87%) for identifying individuals with insufficient iodine intake. The median iodine intake from the screening tool did not differ significantly from that of the food diaries (145 v 140 µg/d; p = 0·07), and the two methods were strongly correlated (r 0·70, p < 0·001). Median completion time was 4 min. The screening tool provides a valid and efficient method for assessing iodine intake in UK adults, incorporating conventional and plant-based sources. It offers a practical approach for identifying individuals at risk of iodine deficiency and for supporting population monitoring and dietary interventions.