Performance of iohexol determination in serum and urine by HPLC: Validation, risk and uncertainty assessment

BackgroundDetermination of glomerular filtration rate plays an important role in nephrological practice. Iohexol is a reference marker for glomerular filtration rate determination. It is available and safe. The aim of this study was to develop a simple, efficient and easy to use analytical method for the quantification of iohexol in serum and urine by high performance liquid chromatography and to thoroughly validate this method.MethodsThe HPLC method was inspired from the method published by Krutzen. The e.noval software V2.0 (Arlenda, Liège, Belgium) was used to compute all validation results.ResultsThe validation results indicate that the method will give accurate and reliable results for serum values ranging from 12.95 to 1295 µg/ml and for urine values ranging from 86.0 to 4144 µg/ml. In routine practice, iohexol concentrations found in plasma after injection range from 40 to 600 µg/ml. The expected urinary values are much wider. One should not hesitate to dilute urine samples to fit with the validated range over 5000 µg/ml.ConclusionThis is the first time that a reference method for the determination of GFR is validated with such a rigorous and thorough protocol. Contrary to other GFR markers, iohexol is now strongly validated from an analytical point of view.