title: Determining median urinary iodine concentration that indicates adequate iodine intake at population level.
abstract: OBJECTIVE
  Urinary iodine concentration is the prime indicator of nutritional iodine status and is used to evaluate population-based iodine supplementation. In 1994, WHO, UNICEF and ICCIDD recommended median urinary iodine concentrations for populations of 100- 200 micro g/l, assuming the 100 micro g/l threshold would limit concentrations <50 micro g/l to </=20% of people. Some scientists felt this proportion was unacceptably high and wanted to increase the threshold above 100 micro g/l. The study was carried out to determine the frequency distribution of urinary iodine in iodine-replete populations (schoolchildren and adults) and the proportion of concentrations <50 micro g/l.
  
  
  METHODS
  A questionnaire on frequency distribution of urinary iodine in iodine-replete populations was circulated to 29 scientific groups.
  
  
  RESULTS
  Nineteen groups reported data from 48 populations with median urinary iodine concentrations >100 micro g/l. The total population was 55 892, including 35 661 (64%) schoolchildren. Median urinary iodine concentrations were 111-540 (median 201) micro g/l for all populations, 100-199 micro g/l in 23 (48%) populations and >/=200 micro g/l in 25 (52%). The frequencies of values <50 micro g/l were 0-20.8 (mean 4.8%) overall and 7.2% and 2.5% in populations with medians of 100-199 micro g/l and >200 micro g/l, respectively. The frequency reached 20% only in two places where iodine had been supplemented for <2 years.
  
  
  CONCLUSIONS
  The frequency of urinary iodine concentrations <50 micro g/l in populations with median urinary iodine concentrations >/=100 micro g/l has been overestimated. The threshold of 100 micro g/l does not need to be increased. In populations, median urinary iodine concentrations of 100-200 micro g/l indicate adequate iodine intake and optimal iodine nutrition.
authors.affiliation: International Council for Control of Iodine Deficiency Disorders, Brussels, Belgium. fdelange@ulb.ac.be
authors.forename: François
authors.initials: F
authors.lastname: Delange
authors.forename: Bruno
authors.initials: B
authors.lastname: de Benoist
authors.forename: Hans
authors.initials: H
authors.lastname: Burgi
mesh_terms: D000328:Adult; D002648:Child; D003677:Deficiency Diseases / Q000453:epidemiology / Q000652:urine*; D005260:Female; D014943:Global Health; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency / Q000652:urine*; D008297:Male; D009752:Nutritional Status; D011159:Population Surveillance; D012016:Reference Values; D011795:Surveys and Questionnaires
chemical_list: D007455:Iodine