Renal and extrarenal clearance of99mTc-MAG3: A comparison with125I-OIH and51Cr-EDTA in patients representing all levels of glomerular filtration rate

Abstract

. This investigation was undertaken in order to determine whether the clearance of technetium-99m mercaptoacetyltriglycine (99mTc-MAG3) is more closely correlated to the clearance of iodine-125 orthoiodohippurate (125I-OIH) than to the clearance of chromium-51 ethylene diamine tetra-acetate (51Cr-EDTA) and whether there is a clinically significant extrarenal clearance of 99mTc-MAG3 . Fifty-one patients with a glomerular filtration rate (GFR) of 4-132ml/min were studied. After a simultaneous single injection of the three tracers, plasma clearance was measured from blood samples 0-5h post injection (p.i.) (0-24h in patients with GFR<15ml/min). Renal plasma clearance was measured 0-5h p.i. The ratio between the renal plasma clearance of 99mTc-MAG3 and 125I-OIH was 0.57. The ratio between the renal plasma clearance of 99mTc-MAG3 and 51Cr-EDTA was 2.57. The coefficient of variation (CV) of the 99mTc-MAG3/125I-OIH ratio was significantly smaller than the CV of the 99mTc-MAG3/51Cr-EDTA ratio (13.4% versus 31.2%). The corresponding plasma clearance ratios were 0.59 (CV=14.8%) and 2.48 (CV=27.0%). Plasma clearance overestimated renal plasma clearance by 7.0ml/min (5.4%) for 99mTc-MAG3 and by 4.1ml/min (8.4%) for 51Cr-EDTA. The difference in plasma and renal plasma clearance of 125I-OIH of 5.5ml/min did not reach statistical significance. Red blood cell binding of 99mTc-MAG3, 125I-OIH and 51Cr-EDTA was 2.0%, 14.6% and 0.2%, respectively. Protein binding of 99mTc-MAG3, 125I-OIH and 51Cr-EDTA was 86.3%, 61.1% and 5.9%, respectively. The volume of distribution of 99mTc-MAG3, 125I-OIH and 51Cr-EDTA was 16.3%, 27.0% and 19.4% of body weight. In conclusion, the clearances of 99mTc-MAG3 and 125I-OIH are more closely correlated than is the clearance of 99mTc-MAG3 with GFR. Extrarenal clearance of 99mTc-MAG3 is relatively smaller than extrarenal clearance of 51Cr-EDTA. Thus, plasma clearance of 99mTc-MAG3 can be used as a measure of renal tubular function.

Simultaneous technetium-99 MAG3, iodine-131-orthoiodohippurate and iodine-125 iothalamate clearance and biodistribution after bolus injection in rats

“…The higher degree of binding to plasma protein of [ 99m Tc]MAG 3 compared with that of [ 131 I]OIH can explain the [3,21,23]. Both compounds are extracted mainly by tubular secretion; thus, the lower renal extraction fraction for [ 99m Tc]MAG 3 may be related to its slower dissociation from binding sites (blood proteins) or to a lower affinity for the tubular transport system compared with [ 131 I]OIH.…”

Reproducibility of technetium-99m mercaptoacetyltriglycine clearance in patients with impaired renal function

“…Subsequently, 10 blood samples (5,12,17,27,37,44, 60, 90, 120 and 180 min post-injection) of 5 ml were drawn into heparinized tubes through an indwelling catheter with a three-way stopcock from the contralateral arm; the catheter was rinsed with saline after each blood sampling. Subsequently, 10 blood samples (5,12,17,27,37,44, 60, 90, 120 and 180 min post-injection) of 5 ml were drawn into heparinized tubes through an indwelling catheter with a three-way stopcock from the contralateral arm; the catheter was rinsed with saline after each blood sampling.…”

“…The utility of 99m Tc-MAG3 clearance has been extensively investigated in several studies [4][5][6], and it has been shown that the clearance of 99m Tc-MAG3 is closely correlated with the clearance of [ 131 I]OIH [6][7][8][9]. However, it has generally been reported that, although 99m Tc-MAG3 has very good accuracy [7][8][9][10][11][12], the results in terms of reproducibility are still controversial [13][14][15][16][17][18][19]. The reproducibility of the study is especially important in patients with renal failure in order to determine whether changes in renal function in serial measurements are related to progression, regression, resolution of the disease or poor reproducibility of the test.…”

How Measuring Glomerular Filtration Rate? Comparison of Reference Methods

“…Most of the authors consider that 51 Cr-EDTA is not binding to proteins (<0,5% (Brochner-Mortensen, 1978;Bailey et al, 1970;Garnett et al, 1967;Stacy & Thorburn, 1966;Forland et al, 1966;Kempi & Persson, 1975;Forland et al, 1966)) even if Rehling described a binding to protein of 10% (Rehling et al, 1995;Rehling et al, 2001). Due to its low molecular weight, 51 Cr-EDTA is freely filtrated through the glomerulus.…”

“…Jagenburg had also calculated an extra-renal clearance of 2 mL/min in two anuric dialysis patients (Jagenburg et al, 1978). Only, Rehling described a higher extra-renal clearance at 8.4% (Rehling et al, 1995). Measurement of 51 Cr-EDTA by nuclear count is very precise and easy because 51 Cr-EDTA half time is long (27 days) (Chantler et al, 1969).…”