Iohexol as a marker of glomerular filtration rate in patients with diabetes: comparison of multiple and simplified sampling protocols.
OBJECTIVE
To report on the reproducibility of iohexol glomerular filtration rate (GFR) estimation, to compare the plasma clearance of iohexol with that of[51Cr]EDTA and to evaluate the reliability of reduced sampling schedules in estimating GFR in Type 1 and Type 2 diabetes mellitus.


METHODS
Agreement was assessed in 15 Type 1 and 26 Type 2 diabetics with creatinine ranging from 53 to 564 micromol/l.


RESULTS
The regression between multiple-sample iohexol and[51Cr]EDTA clearances was 0.999 in Type 1 and 0.987 in Type 2 diabetes (P < 0.0001 for both). A seven-sample design and the three-sample approach by Brøchner-Mortensen were validated by comparison with the full-sample schedule in 87 patients (51 Type 1, 36 Type 2). Full-sample GFR was 80.3 +/- 43.8, seven-sample 79.5 +/- 43.9 (r = 0.990) and three-sample 79.8 +/- 45.2 ml.min-1.1.73 m-2 (r = 0.972). The coefficients of variation of GFR were 2.7 +/- 1.4% and 3.8 +/- 1.9% for the full-sample and the seven-sample approaches, respectively, and significantly higher for the three-sample design (6.9 +/- 3.4%, P = 0.0001).


CONCLUSIONS
After iohexol injection, the Brøchner-Mortensen schedule does not provide an accurate estimate of GFR. The seven-sample approach gives acceptable errors and allows a good estimate of GFR throughout a wide range of renal function.
Department of Endocrinology and Metabolism, University of Pisa, and Cisanello Hospital of Pisa Azienda Ospedaliera Pisana, Pisa, Italy.
L
L
Pucci
S
S
Bandinelli
M
M
Pilo
M
M
Nannipieri
R
R
Navalesi
G
G
Penno
D000328:Adult; D000704:Analysis of Variance; D002860:Chromium Radioisotopes / Q000493:pharmacokinetics; D003287:Contrast Media; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004492:Edetic Acid / Q000493:pharmacokinetics; D005260:Female; D005919:Glomerular Filtration Rate; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007472:Iohexol / Q000493:pharmacokinetics*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D012044:Regression Analysis; D015203:Reproducibility of Results
D002860:Chromium Radioisotopes; D003287:Contrast Media; D004492:Edetic Acid; D006442:Glycated Hemoglobin; D007472:Iohexol