title: Evaluation of sample bias for measuring plasma iohexol clearance in kidney transplantation.
abstract: BACKGROUND
  Plasma clearance of iohexol (PCI) is becoming a commonly used standard tool in many clinical trials to evaluate the glomerular filtration rate (GFR). However, most studies performing PCI use only early plasma samples (2, 3, and 4 hr). This study aims to evaluate the role of early and late plasma sampling in the precision of PCI calculation in transplant recipients.
  
  
  METHODS
  We evaluated 342 renal transplant recipients for both renal clearance (RC) and plasma clearance, using iohexol and six blood samples (2, 3, 4, 5, 6, and 24 hr). Patients were divided into three subgroups according to RC: <30, 30 to 60, and >60 mL/min/1.75 m(2).
  
  
  RESULTS
  A simplified technique using early plasma samples overestimated GFR with a mean difference between plasma clearance and RC of 53.3%, 25.7%, and 12.5% for the three subgroups, respectively. This difference decreased to 8.8%, 6.3%, and 5.5%, respectively, when the 24-hr sample was included in plasma clearance calculation.
  
  
  CONCLUSIONS
  These results demonstrate that GFR evaluation by PCI in renal transplant recipients requires a late plasma sample.
authors.affiliation: Division of Nephrology and Transplantation, Centre Hospitalier et Universitaire, Reims, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Stolz
authors.forename: Guillaume
authors.initials: G
authors.lastname: Hoizey
authors.forename: Olivier
authors.initials: O
authors.lastname: Toupance
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lavaud
authors.forename: Fabien
authors.initials: F
authors.lastname: Vitry
authors.forename: Jacques
authors.initials: J
authors.lastname: Chanard
authors.forename: Philippe
authors.initials: P
authors.lastname: Rieu
mesh_terms: D000328:Adult; D019540:Area Under Curve; D015982:Bias; D001774:Blood Chemical Analysis / Q000379:methods*; D003287:Contrast Media / Q000378:metabolism*; D003404:Creatinine / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007472:Iohexol / Q000378:metabolism*; D016030:Kidney Transplantation / Q000502:physiology*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged
chemical_list: D003287:Contrast Media; D007472:Iohexol; D003404:Creatinine