Validation of an enzyme-linked immunosorbent assay for measuring iohexol in canine serum as a marker for intestinal permeability and glomerular filtration rate.

Iohexol is a non-radioactive, water-soluble, iodinated radiographic contrast medium that is widely used in detection imaging for both the scientific and clinical purposes. Iohexol is also frequently used as a marker for glomerular filtration rate (GFR) in both humans and animals, such as dogs and cats; but also as intestinal permeability (IP) marker in humans, dogs, horses and rats. Even though there are different detection tests for assessing the GFR and IP, a highest validation method is required. Therefore, the aim of this study was to determine the FIT-GFR Iohexol Kit (ELISA) accuracy for the measurement of iohexol in canine serum, and to compare it to both high-performance liquid chromatography (HPLC) and neutron activation analysis (NAA). Blank and iohexol-containing blood samples (n=100) from Beagles dogs were collected from the jugular vein in lithium heparin tubes before and after intravenous application of 3.0 g iohexol/dog to the cephalic vein. The results of this study showed that the correlation coefficients when comparing ELISA vs. HPLC (r=0.99), ELISA vs. NAA (r=0.99) and HPLC vs. NAA (r=0.98) were all excellent. We conclude that measurement of iohexol from canine serum using the FIT-GFR Iohexol Kit is as reproducible and reliable as using HPLC or NAA. Nonetheless, using ELISA for measuring iohexol may be more practical, economical and useful than using HPLC or NAA.