Dried blood spot thyroglobulin as a biomarker of iodine status in pregnant women

Context: Thyroglobulin (Tg) may be a sensitive biomarker of iodine nutrition in pregnant women (PW). A dried blood spot (DBS) assay would simplify collection and transport in field studies. Objectives: Our aims were to: 1) establish a reference range for DBS-Tg in iodine-sufficient PW; 2) test this reference range in PW with a range of iodine intakes; and 3) determine if co-measurement of Tg antibodies (Ab) is necessary to define population iodine status. Design, Settings and Participants: Standardized cross-sectional studies in 3870 PW from 11 countries with iodine intakes from deficient to more-than-adequate. To define the DBS-Tg reference range we included euthyroid, TgAb-negative PW (n=599) from 3 countries with sufficient iodine intakes. Main Outcome Measures: We measured urinary iodine concentration (UIC) and DBS TSH, total T4, Tg and TgAb. Results: In the reference PW population, median DBS-Tg (95%CI) was 9.2 (8.7–9.8) μg/L and was not significantly different between trimesters; the reference range...