title: A simple LC-MS method for the determination of iohexol and iothalamate in serum, using ioversol as an internal standard.
abstract: BACKGROUND
  Chronic kidney disease (CKD) is diagnosed and explored through the determination of the glomerular filtration rate (GFR). Our goal was to develop a simple LC-MS method for the determination in serum of 2 popular GFR markers, contrast agents iohexol and iothalamate, for routine use and comparison studies between the two markers. A similar contrast agent, ioversol, was used as an internal standard and the method underwent a rigorous validation protocol based on β-expectation tolerance intervals.
  
  
  METHODS
  We adapted the HPLC-UV method from Cavalier et al. to our LC-MS system. Data treatment for the validation was performed using Multiquant 3.0 (Sciex, Framingham, MA, USA) and e.noval 3.0 software (Arlenda, Liège, Belgium).
  
  
  RESULTS
  According to the validation results our method will give accurate and reliable results for concentrations ranging from 6.8 to 250μg/ml for iohexol and 6.15μg/ml to 250μg/ml for iothalamate. In our practice these intervals are sufficient to determine both compounds in most patient samples. Samples with higher detected concentrations can always be diluted into range.
  
  
  CONCLUSIONS
  With its internal standard and extensive validation, our method is now ready for routine and clinical research use.
authors.affiliation: Department of Clinical Chemistry, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium.
authors.forename: Laurent
authors.initials: L
authors.lastname: Nyssen
authors.affiliation: Department of Nephrology and Hypertension, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Delanaye
authors.affiliation: Department of Clinical Chemistry, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Le Goff
authors.affiliation: Department of Clinical Chemistry, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Peeters
authors.affiliation: Department of Clinical Chemistry, University of Liège, CHU Sart-Tilman, 4000 Liège, Belgium. Electronic address: etienne.cavalier@chu.ulg.ac.be.
authors.forename: Étienne
authors.initials: É
authors.lastname: Cavalier
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007472:Iohexol / Q000032:analysis* / Q000737:chemistry; D007483:Iothalamic Acid / Q000032:analysis* / Q000737:chemistry; D013058:Mass Spectrometry; D012015:Reference Standards; D014283:Triiodobenzoic Acids / Q000032:analysis* / Q000592:standards
chemical_list: D014283:Triiodobenzoic Acids; D007483:Iothalamic Acid; D007472:Iohexol; C054871:ioversol
keywords: Glomerular filtration rate; Iohexol; Iothalamate; Ioversol; LC-MS; Nephrology