Rapid Test Kit for Measurement of Urinary Iodine

Lynntech, Inc., College Station TX

Investigators

Abstract

Iodine is an essential micronutrient and an integral component of thyroid hormones. Iodine is obtained through the diet and is mainly absorbed by the gastrointestinal tract as the inorganic anion, iodide. An accurate assessment of population iodine status is necessary to inform public health policies and clinical research on iodine nutrition. Urinary iodine concentration (UIC) directly reflects dietary iodine intake and is the most common indicator used worldwide to assess population iodine status. Clinical laboratory tests of thyroid function are sometimes used as indicators of iodine status, although such use is often problematic. Even in severely iodine-deficient regions, there is a great deal of intra-individual variation in the ability of the thyroid to adapt. In most settings and in most population subgroups other than newborns, thyroid function tests are not considered sensitive indicators of population iodine status. However, the thyroid-derived protein thyroglobulin is increasingly being used for this purpose. UIC is currently a well validated population biomarker for iodine status, but individual biomarkers that could be used for research, patient care, and public health are lacking. Several methods for determination of UIC are available. However, currently used methods for urinary iodine measurement either require expensive instrumentation with qualified personnel (inductively coupled plasma-mass spectrometry, instrumental nuclear activation analysis) or oxidative sample digestion to remove potential interferences prior to analysis by a kinetic colorimetric method originally introduced by Sandell and Kolthoff. The Sandell?Kolthoff method is based on the catalytic effect of iodide on the reaction between Ce4+ and As3+. UIC has also been measured using ion selective electrodes, but it required removal of chloride ions from the urine sample by a chromatographic process. In addition, the ion selective and reference electrodes are prone to fouling and requires highly skilled personnel for use and maintenance. Lynntech is proposing to develop a simple innovative method for rapid and accurate measurement of urinary iodine concentration. This method will utilize convenient and disposable dry reagent cartridges for sample conditioning and iodine level determination, and eliminates the need for use of corrosive liquid reagents. Proposed method for determination of urinary iodine involves three simple steps. First, pass urine sample through an ion exchange cartridge for iodide extraction. Second, pass a small volume of an eluent (salt water) through the ion exchange cartridge, reagent cartridge and detection cartridge in series for elution of iodide, oxidation of iodide to iodine and capture iodide on a detection membrane. Third, measure iodine concentration using a colorimeter. Because of the ease of use and low cost this technology can potentially make a significant impact on public health by making it possible to conveniently measure UIC much more frequently and providing accurate assessment of iodine deficiency at an individual basis.