title: Potentiometric measurement of urinary iodine concentration in patients with thyroid diseases with and without previous exposure to non-radioactive iodine.
abstract: BACKGROUND
  Extensive application of measurement of urinary iodine concentration (UIC) in several benign and malignant thyroid diseases could profit by the availability of rapid and inexpensive measuring techniques. Aim of this study was to apply a simple and inexpensive commercially available potentiometric method for the quantification of UIC based on iodine-specific ion-selective electrodes (ISE) in patients with thyroid diseases.
  
  
  METHODS
  This retrospective study included patients with differentiated thyroid cancer (n=286) and patients with hyperthyroidism of different etiologies (n=203). Within the whole sample (n=489) 20 patients had previously (1 week-6 months) been exposed to iodine overload, either from contrast media (n=8) or amiodarone (n=12).
  
  
  RESULTS
  In patients not exposed to iodine, the histogram showed that the distribution of UIC violated normality. The peak of the curve occurred between 5.0 μmol/L and 6.0 μmol/L. Variability was sizeable (percent coefficient of variation, %CV: 66%, 95% confidence interval: 1.48-18.72 μmol/L). The group of exposed patients could be easily distinguished from not exposed patients (median UIC: 47.5 μmol/L vs. 5.42 μmol/L). UIC was significantly correlated to urinary creatinine concentration, but normalization to urinary creatinine increased the inter-subject variability of UIC (%CV=96% vs. 66%). In test-retest studies (n=25) the intra-class correlation coefficient was 0.73 for UIC, 0.82 for creatinine and 0.64 for the UIC: creatinine ratio.
  
  
  CONCLUSIONS
  Iodine-specific ISE-based potentiometric methods can be successfully applied as an alternative to existing methods in patients with thyroid diseases. The promising characteristics of the method need to be confirmed in future larger prospective studies.
authors: Giampiero
authors: G
authors: Giovacchini
authors: Luca
authors: L
authors: Giovanella
authors: Andreas
authors: A
authors: Haldemann
authors: Uwe
authors: U
authors: Staub
authors: Frank G
authors: FG
authors: Füchsel
authors: Peter
authors: P
authors: Koch
mesh_terms: D005260:Female; D006801:Humans; D007455:Iodine / Q000008:administration & dosage* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011199:Potentiometry / Q000295:instrumentation; D011786:Quality Control; D012189:Retrospective Studies; D013959:Thyroid Diseases / Q000652:urine*
chemical_list: D007455:Iodine