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Published on: May 10, 2013
One-sample determination of glomerular filtration rate (GFR) in children. An evaluation based on 75 consecutive
Ulrik L Henriksen1, Inge-Lis Kanstrup, Jens H Henriksen
1Departments of Clinical Physiology and Nuclear Medicine , Hvidovre.
Insights
One-sample glomerular filtration rate (GFR) measurements show excellent agreement with multiple-sample methods in most children. However, a small percentage of children exhibit significant discrepancies, necessitating multiple-sample GFR determination when accuracy is critical.
Area of Science:
- Pediatric Nephrology
- Renal Function Assessment
- Diagnostic Accuracy
Background:
- Accurate determination of glomerular filtration rate (GFR) is clinically vital for managing pediatric nephro-urological disorders.
- The (51)Cr-EDTA clearance test is a reference standard for GFR measurement.
Purpose of the Study:
- To compare the accuracy of a simplified one-sample GFR method against the established multiple-sample (51)Cr-EDTA clearance in children.
- To evaluate the reliability of one-sample GFR in pediatric patients with kidney conditions.
Main Methods:
- Seventy-five children (age ½-13 years) underwent (51)Cr-EDTA injection with serial plasma sampling.
- Multiple-sample clearance was calculated using the injected dose/plasma radioactivity area under the curve.
- One-sample clearance was derived from a single plasma sample at 60, 90, or 120 minutes post-injection.
Main Results:
- Overall, one-sample GFR demonstrated excellent accuracy, with mean differences of 0.7-1.7 mL/min compared to the reference.
- In 85% of children, one-sample GFR values were within ± 4 mL/min of the multiple-sample reference.
- A notable 15% of children showed discrepancies exceeding 4 mL/min (range 4.4-19.5 mL/min), unexplained by various clinical or analytical factors.
Conclusions:
- The one-sample GFR method provides reliable estimates in the majority of pediatric patients.
- Unexpectedly large discrepancies in a subset of children highlight potential limitations of the simplified method.
- For critical clinical decisions requiring precise GFR values, the multiple-sample clearance method remains the gold standard.
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 (51)Cr-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 (51)Cr-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.
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