title: Urinary iodine: comparison of a simple method for its determination in microplates with measurement by inductively-coupled plasma mass spectrometry.
abstract: The aim of our study was to develop and validate an inexpensive, rapid, easy to use quantitative method to determine urinary iodine without major procurement costs for equipment. The rationale behind introducing this method is the increasing demand for urinary iodine assessments. Our study included 103 patients (76 female, 27 male), age (arithmetic mean) 52 ± 17.3 years. Urinary iodine was determined in microplates by a modification of the Sandell-Kolthoff reaction. The results were compared with inductively-coupled plasma mass spectrometry (ICP-MS) for iodine, considered as reference method. Geometric mean of urinary iodine determined by the Sandell-Kolthoff reaction method was 62.69 μg/l (95% confidence interval 53.16-73.92) whereas by the ICP-MS method it was 65.53 μg/l (95% confidence interval 54.77-78.41). Passing-Bablok regression equations for both methods gave y = 3.374 + 0.873x (y: Sandell-Kolthoff method, x: ICP-MS). Spearman´s correlation coefficient was 0.981, indicating a very high degree of agreement between the two methods. Bland-Altman plots showed no significant systematic difference between the two methods. The modified Sandell-Kolthoff method using microtiter plate technique presented here is a simple, inexpensive semi-automated method to determine urinary iodine with very little toxic waste. Comparison with the ICP-MS-technique yielded a good agreement between the two methods.
authors.affiliation: Internal Medicine IV (Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry), Eberhard-Karls-University, Tübingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Haap
authors.affiliation: Labor Dr. Limbach &Kollegen, GbR, Medizinisches Versorgungszentrum, Im Breitspiel 15, 69126 Heidelberg, Germany.
authors.forename: Heinz Jürgen
authors.initials: HJ
authors.lastname: Roth
authors.affiliation: Labor Dr. Limbach &Kollegen, GbR, Medizinisches Versorgungszentrum, Im Breitspiel 15, 69126 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Huber
authors.affiliation: Department of Nuclear Medicine, Eberhard-Karls-University, Tübingen, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Dittmann
authors.affiliation: Internal Medicine IV (Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry), Eberhard-Karls-University, Tübingen, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Wahl
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007455:Iodine / Q000652:urine*; D008297:Male; D013058:Mass Spectrometry / Q000379:methods / Q000592:standards; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods / Q000592:standards; D016482:Urinalysis / Q000379:methods* / Q000592:standards
chemical_list: D007455:Iodine