title: A simple micro-photometric method for urinary iodine determination.
abstract: BACKGROUND
  Urinary iodide concentration (UIC) is useful to evaluate nutritional iodine status. In clinical settings UIC helps to exclude blocking of the thyroid gland by excessive endogenous iodine, if diagnostic or therapeutic administration of radio-iodine is indicated. Therefore, this study established a simple test for the measurement of UIC.
  
  
  METHODS
  UIC was analyzed in urine samples of 200 patients. Samples were pre-treated at 95°C for 45 min with ammonium persulfate in a thermal cycler, followed by a photometric Sandell-Kolthoff reaction (SK) carried out in microtiter plates. For method comparison, UIC was analyzed in 30 samples by inductivity coupled plasma mass spectro-metry (ICP-MS) as a reference method.
  
  
  RESULTS
  Incubation conditions were optimized concerning recovery. The photometric test correlated well to the reference method (SK=0.91*ICP-MS+1, r=0.962) and presented with a functional sensitivity of 20 μg/L. UIC of patient samples ranged from <20 to 750 μg/L (median 110 μg/L); 90% of the urine samples had iodide concentrations below 210 μg/L.
  
  
  CONCLUSIONS
  The modified SK-test takes approximately 90 min for analyses of 20 urine samples compared with 27 h for ICP-MS. The photometric test provides satisfactory results and can be performed with the basic equipment of a clinical laboratory.
authors.affiliation: Department of Laboratory Medicine, Medical University of Vienna and the General Hospital of the City of Vienna, Vienna, Austria. gabriele.grimm@meduniwien.ac.at
authors.forename: Gabriele
authors.initials: G
authors.lastname: Grimm
authors.forename: Heidelinde
authors.initials: H
authors.lastname: Lindorfer
authors.forename: Heidi
authors.initials: H
authors.lastname: Kieweg
authors.forename: Rodrig
authors.initials: R
authors.lastname: Marculescu
authors.forename: Martha
authors.initials: M
authors.lastname: Hoffmann
authors.forename: Alois
authors.initials: A
authors.lastname: Gessl
authors.forename: Manfred
authors.initials: M
authors.lastname: Sager
authors.forename: Christian
authors.initials: C
authors.lastname: Bieglmayer
mesh_terms: D019411:Clinical Laboratory Techniques / Q000379:methods*; D006801:Humans; D007455:Iodine / Q000652:urine*; D010783:Photometry; D013997:Time Factors
chemical_list: D007455:Iodine