Evaluation of sample bias for measuring plasma iohexol clearance in kidney transplantation.
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.
Stolz
Arnaud
A
Division of Nephrology and Transplantation, Centre Hospitalier et Universitaire, Reims, France.
Hoizey
Guillaume
G
Toupance
Olivier
O
Lavaud
Sylvie
S
Vitry
Fabien
F
Chanard
Jacques
J
Rieu
Philippe
P
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
D003287:Contrast Media; D007472:Iohexol; D003404:Creatinine