Reliability of ⁵¹Cr-EDTA plasma and urinary clearance as a measure of residual renal function in dialysis patients

Abstract

Purpose: In dialysis patients, longer survival is associated with a higher residual renal function. Randomized controlled trials are conducted to clarify how residual renal function can be preserved. However, existing methods for measuring residual renal function are uncertain and there is a need for establishing a standard for measurements of glomerular filtration rate (GFR) in dialysis patients. Methods: ⁵¹Cr-EDTA clearances in plasma, urine, and dialysate were evaluated in a sample of 12 hemodialysis and 12 peritoneal dialysis patients. The patients’ condition was generally stable, and all patients were investigated twice within 4–10 days. Results: Plasma clearances of ⁵¹Cr-EDTA for all patients ranged between 2.1 and 30.8 mL/min/1.73m², whereas urinary ⁵¹Cr-EDTA clearances ranged from 0.7–20.0 mL/min/1.73m². This difference was statistically significant (p < 0.001). Week-to-week reproducibility expressed as coefficients of variation were below or equal to 10% for plasma clearances and 13% for urinary clearances in hemodialysis patients and 14% in peritoneal dialysis patients. Conclusions: This study demonstrated a difference between ⁵¹Cr-EDTA plasma and urinary clearances in dialysis patients. Plasma clearance of ⁵¹Cr-EDTA had the best reproducibility. For repeated measurements as in clinical prospective trials, we recommend ⁵¹Cr-EDTA plasma clearance based on blood sampling at 5 + 24 hours with subtraction of ⁵¹Cr-EDTA dialysate clearance in peritoneal dialysis patients. Further studies are needed to corroborate our findings.

Key Words::

• Adult
• chromium radioisotopes
• chronic kidney failure
• female
• glomerular filtration rate
• humans
• male
• renal dialysis
• reproducibility of results

Acknowledgements

We would like to thank Lene E. Nielsen for invaluable help with ⁵¹Cr-EDTA clearance calculations, and also Karin Hansen, Ilse Rasmussen, Lotte Paaby, and Lisbeth Holt at the Research Laboratory at the Department of Renal Medicine for helping with sampling blood, urine and dialysate. I appreciate the teaching and supervision given by biostatistician at Aarhus University, Mogens Erlandsen.

Grants from the Institute of Clinical Medicine at Aarhus University and the Danish Kidney Association made this study possible.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.