Interference of preservatives on urinary iodine measurement by Sandell-Kolthoff method.

This report aimed to determine the effects of different preservatives used to maintain the integrity of urine samples for a 24-hour urine collection on urinary iodine measurement by the Sandell-Kolthoff method in vitro. The selected preservatives were hydrochloric acid, acetic acid, boric acid, sodium carbonate, sodium fluoride, thymol with isopropanol, sodium chloride with formalin, and Saccomanno fixative. The test samples to which these preservatives were added and the control samples for basal measurements were prepared from the urine pool obtained from urine samples taken from healthy volunteers. The urinary iodine measurements were performed following the calculated minimum number of replicates in these prepared samples. The data analysis of the interferences of the preservatives was performed based on the Clinical and Laboratory Standards Institute EP7-A2 guideline. The preservatives that had more acceptable effects on the urinary iodine measurement compared to the others were sodium carbonate (0.5% w/v) and thymol (10% w/v) with isopropanol (0.25% v/v) for 24-hour storage at room temperature. This report presented reliable and usable data revealing the effects of preservatives, which are frequently used to maintain the integrity of urine samples for a 24-hour urine collection, on urinary iodine measurement. There are need to reveal the possible effects of potential exogenous interfering substances and the pathological levels of endogenous analytes or shaped elements in the urine matrix on methods with routine clinical use in making medical decisions.