title: Assessment of iodine status using dried blood spot thyroglobulin: development of reference material and establishment of an international reference range in iodine-sufficient children.
abstract: BACKGROUND
  Thyroglobulin (Tg) may be a valuable indicator of improving thyroid function in children after salt iodization. A recently developed Tg assay for use on dried whole blood spots (DBS) makes sampling practical, even in remote areas.
  
  
  OBJECTIVE
  The study aim was to develop a reference standard for DBS-Tg, establish an international reference range for DBS-Tg in iodine-sufficient children, and test the standardized DBS-Tg assay in an intervention trial.
  
  
  METHODS
  Serum Tg reference material of the European Community Bureau of Reference (CRM-457) was adapted for DBS and its stability tested over 1 yr. DBS-Tg was determined in an international sample of 5- to 14-yr-old children (n = 700) who were euthyroid, anti-Tg antibody negative, and residing in areas of long-term iodine sufficiency. In a 10-month trial in iodine-deficient children, DBS-Tg and other indicators of iodine status were measured before and after introduction of iodized salt.
  
  
  RESULTS
  Stability of the CRM-457 Tg reference standard on DBS over 1 yr of storage at -20 and -50 C was acceptable. In the international sample of children, the third and 97th percentiles of DBS-Tg were 4 and 40 microg/liter, respectively. In the intervention, before introduction of iodized salt, median DBS-Tg was 49 microg/liter, and more than two thirds of children had DBS-Tg values greater than 40 microg/liter. After 5 and 10 months of iodized salt use, median DBS-Tg decreased to 13 and 8 microg/liter, respectively, and only 7 and 3% of children, respectively, had values greater than 40 microg/liter. DBS-Tg correlated well at baseline and 5 months with urinary iodine and thyroid volume.
  
  
  CONCLUSIONS
  The availability of reference material and an international reference range facilitates the use of DBS-Tg for monitoring of iodine nutrition in school-age children.
authors.affiliation: Laboratory for Human Nutrition, Swiss Federal Institute of Technology, LFV E19, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zimmermann
authors.forename: Bruno
authors.initials: B
authors.lastname: de Benoist
authors.forename: Sandro
authors.initials: S
authors.lastname: Corigliano
authors.forename: Pieter L
authors.initials: PL
authors.lastname: Jooste
authors.forename: Luciano
authors.initials: L
authors.lastname: Molinari
authors.forename: Khairya
authors.initials: K
authors.lastname: Moosa
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Pretell
authors.forename: Zuhair Salman
authors.initials: ZS
authors.lastname: Al-Dallal
authors.forename: Yao
authors.initials: Y
authors.lastname: Wei
authors.forename: Chen
authors.initials: C
authors.lastname: Zu-Pei
authors.forename: Toni
authors.initials: T
authors.lastname: Torresani
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003677:Deficiency Diseases / Q000178:diet therapy; D005062:European Union / Q000458:organization & administration; D005260:Female; D006801:Humans; D007455:Iodine / Q000097:blood* / Q000172:deficiency / Q000627:therapeutic use / Q000652:urine; D008297:Male; D012015:Reference Standards; D012016:Reference Values; D017673:Sodium Chloride, Dietary / Q000627:therapeutic use; D013954:Thyroglobulin / Q000032:analysis*; D013959:Thyroid Diseases / Q000178:diet therapy; D013960:Thyroid Function Tests / Q000379:methods / Q000592:standards*; D014944:World Health Organization / Q000458:organization & administration
chemical_list: D017673:Sodium Chloride, Dietary; C034024:iodized salt; D013954:Thyroglobulin; D007455:Iodine