Methods for measuring iodine in urine and serum

Summary

The most important information in the determination of the status of iodine nutrition of a population comes from the measurement of the urinary excretion of iodine. Several methods are available for measuring urinary iodine. The choice among methods depends on the intended application, the number of samples, the cost and the technical capability. Epidemiological field studies demand simple, rapid and cost-effective methods. Suitable for these applications are the rapid urinary iodide test and the ammonium persulfate oxidation method which gives comparable results to the chloric acid method without having the drawbacks of being hazardous and explosive. In research studies however, sophisticated automated technology like the Technicon Autoanalyzer or Paired-Ion Reversed Phase HPLC are used in which the high cost of instrumentation are outweighed by the benefits of processing a large number of samples with high accuracy and minimal technician time.

For determining serum inorganic iodide (SII) the HPLC assay is the method of choice, because contaminations from the protein bound iodine fraction do not interfere with the detection process. The clinical relevance of the measurement of SII is limited, but allows the calculation of the absolute iodine uptake which has great value in pathophysiologic studies.

Keywords

Urinary iodine - serum inorganic iodide - liquid chromatography - ammonium persulfate - rapid urinary iodide test