One-sample determination of glomerular filtration rate (GFR) in children. An evaluation based on 75 consecutive patients

Abstract

Background and aim. From a clinical point of view determination of glomerular filtration rate (clearance) is important. The aim of the present study was to compare the one-sample clearance to reference multiple-sample ⁵¹Cr-EDTA clearance in consecutively referred children suspected of or with established nephro-urological disorders. Material and methods. A total of 75 children, age ½–13 years, received a quantitative intravenous injection of ⁵¹Cr-EDTA followed by six plasma samples 10–120 min after injection. The multiple-sample clearance was measured as injected dose relative to the area under the plasma radioactivity curve. The one-sample clearance was determined from a single plasma sample collected at 60, 90 or 120 min after injection according to the one-pool method. Results. The overall accuracy of one-sample clearance was excellent with mean numeric difference to the reference value of 0.7–1.7 mL/min. In 64 children, the one-sample clearance was within ± 4 mL/min of the multiple-sample value. However, in 11 children the numeric difference exceeded 4 mL/min (4.4–19.5). Analysis of age, body size, distribution volume, indicator retention time, clearance level, curve fitting, and sampling time could not explain the observed large difference between one-sample and multiple-sample clearance in these 15% of the children. Conclusion. In the majority of children there is an excellent agreement between one-sample clearance and multiple-sample clearance. However, unexpectedly in a small fraction (15%) larger discrepancies are found. If an accurate clearance value is essential a multiple-sample determination should be performed.

Key Words::

• ⁵¹Cr-EDTA
• glomerular filtration rate
• plasma clearance
• renal function
• slope-intercept technique

Acknowledgements

The authors thankfully acknowledge the skillful assistance of Ms Hanne B. Hansen, MSc, Ms Katja Andersen, technician, and Ms Georgina T. Narvaez, BsC, secretary.

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