TY - JOUR
T1 - Conventional measurements of GFR using Cr-51-EDTA overestimate true renal clearance by 10 percent
AU - Moore, A E B
AU - Park-Holohan, S J
AU - Blake, G M
AU - Fogelman, I
PY - 2003/1/1
Y1 - 2003/1/1
N2 - It is widely believed that measurement of the area under the plasma clearance curve (AUC) following a single intravenous injection of chromium-51 labelled ethylene diamine tetra-acetic acid (Cr-51-EDTA) is a gold standard method for determining glomerular filtration rate (GFR). However, there are reports that Cr-51-EDTA may have a significant extrarenal clearance. The aim of this study was to identify the non-renal component of Cr-51-EDTA plasma clearance contributing to the AUC measurement of GFR. Seventy healthy postmenopausal women (mean age 60 years, range 45-79 years) were injected with 3 MBq Cr-51-EDTA and 0.25 MBq iodine-125 labelled human serum albumin and 11 blood samples taken between 0 and 4 h through an indwelling venous cannula. For the first 21 subjects, two complete urine collections were made 0-2 h and 2-4 h after injection, and for the final 49 patients, four 1-h urine collections were made. The mean Cr-51-EDTA total plasma clearance was 84 ml/min (range 50-132 ml/min). The mean ratio (SEM) of urine to total clearance determined from the cumulative 1-, 2-, 3- and 4-h data was 0.903 (0.018), 0.891 (0.013), 0.898 (0.011) and 0.899 (0.010) respectively and remained constant despite the mean urine concentration decreasing from 122% to 15%/litre during this period. A least squares fit to data from the 238 individual urine collections was used to determine the fraction of the total plasma clearance attributable to renal clearance, alpha(o), and the residual urine volume, DeltaV. The results were alpha(o)=0.910 (95% CI: 0.889-0.932) and DeltaV=14 ml (95% CI: -4 to +34 ml). The overestimation of the true renal clearance of Cr-51-EDTA by the AUC method is believed to be due to the failure of the plasma clearance curve to reach the true terminal exponential by 2 h after injection as usually assumed. As a result, conventional measurements of GFR using Cr-51-EDTA overestimate the true renal clearance of tracer by approximately 10%.
AB - It is widely believed that measurement of the area under the plasma clearance curve (AUC) following a single intravenous injection of chromium-51 labelled ethylene diamine tetra-acetic acid (Cr-51-EDTA) is a gold standard method for determining glomerular filtration rate (GFR). However, there are reports that Cr-51-EDTA may have a significant extrarenal clearance. The aim of this study was to identify the non-renal component of Cr-51-EDTA plasma clearance contributing to the AUC measurement of GFR. Seventy healthy postmenopausal women (mean age 60 years, range 45-79 years) were injected with 3 MBq Cr-51-EDTA and 0.25 MBq iodine-125 labelled human serum albumin and 11 blood samples taken between 0 and 4 h through an indwelling venous cannula. For the first 21 subjects, two complete urine collections were made 0-2 h and 2-4 h after injection, and for the final 49 patients, four 1-h urine collections were made. The mean Cr-51-EDTA total plasma clearance was 84 ml/min (range 50-132 ml/min). The mean ratio (SEM) of urine to total clearance determined from the cumulative 1-, 2-, 3- and 4-h data was 0.903 (0.018), 0.891 (0.013), 0.898 (0.011) and 0.899 (0.010) respectively and remained constant despite the mean urine concentration decreasing from 122% to 15%/litre during this period. A least squares fit to data from the 238 individual urine collections was used to determine the fraction of the total plasma clearance attributable to renal clearance, alpha(o), and the residual urine volume, DeltaV. The results were alpha(o)=0.910 (95% CI: 0.889-0.932) and DeltaV=14 ml (95% CI: -4 to +34 ml). The overestimation of the true renal clearance of Cr-51-EDTA by the AUC method is believed to be due to the failure of the plasma clearance curve to reach the true terminal exponential by 2 h after injection as usually assumed. As a result, conventional measurements of GFR using Cr-51-EDTA overestimate the true renal clearance of tracer by approximately 10%.
UR - http://www.scopus.com/inward/record.url?scp=0038207724&partnerID=8YFLogxK
U2 - 10.1007/s00259-002-1007-y
DO - 10.1007/s00259-002-1007-y
M3 - Article
SN - 1619-7089
VL - 30
SP - 4
EP - 8
JO - European Journal of Nuclear Medicine and Molecular Imaging
JF - European Journal of Nuclear Medicine and Molecular Imaging
IS - 1
ER -