Glomerular filtration rate: comparison of simultaneous plasma clearance of ^99mTc-DTPA and ⁵¹Cr-EDTA revisited

Abstract

The issue of whether ^99mTc-DTPA can replace ⁵¹Cr-EDTA for measurement of plasma clearance as a surrogate for glomerular filtration rate (GFR) is of great relevance to daily clinical practice. Prompted by the shortage of ⁵¹Cr-EDTA we conducted a head-to-head comparison in patients attending our department for GFR determination. The two tracers (3.7 MBq of ⁵¹Cr-EDTA and 8 MBq of ^99mTc-DTPA) were administered intravenously immediately after each other, and the standard number of blood samples were drawn. Fifty-four patients were enrolled. In 51 of these, single-sample measurement was performed with the following results: GFR_EDTA was 84.6 ± 23.3 mL/min, GFR_DTPA was 84.2 ± 24.7 mL/min. The mean difference was 0.4 ± 2.8 mL/min, p = 0.32, and results based on the two tracers were highly correlated (r = 0.995). GFR_DTPA exceeded GFR_EDTA at high GFR values (difference < 0 at GFR_EDTA >91.4 mL/min) and vice versa (difference > 0 at GFR_EDTA < 91.4 mL/min). However, differences fell within few GFR units that most often will have no clinical consequence. We therefore conclude that ^99mTc-DTPA can replace ⁵¹Cr-EDTA for single-sample determination of GFR in a clinical setting.

Keywords:

• GFR
• clearance
• chromium-51
• technetium 99m
• EDTA

Acknowledgements

The skilled technical assistance of Louise Janus is greatly appreciated.