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Glomerular filtration rate by single-injection inulin clearance: definition of a workable protocol for children
D W Swinkels1, J C Hendriks, J Nauta
1Department of Clinical Chemistry, University Hospital Nijmegen, The Netherlands. D.Swinkels@ckcl.azn.nl
Insights
Optimizing glomerular filtration rate (GFR) measurement in children using inulin clearance is possible. A simplified seven-sample schedule with two-compartment analysis provides accurate GFR results efficiently.
Area of Science:
- Pediatric Nephrology
- Renal Physiology
- Diagnostic Methods
Background:
- Glomerular filtration rate (GFR) is a key indicator of kidney function.
- Inulin clearance is a gold standard for GFR determination but can be cumbersome.
- Optimizing GFR measurement in pediatric patients is crucial for accurate diagnosis and management of renal diseases.
Purpose of the Study:
- To optimize the procedure for determining GFR using serum inulin clearance in children.
- To evaluate the suitability of a reduced sampling frequency and a two-compartment model for inulin clearance analysis.
Main Methods:
- Analysis of 117 serum inulin time-decay curves from 59 children (1.3–15.2 years) with renal disease.
- Comparison of one-compartment versus two-compartment models for inulin disappearance curves.
- Assessment of a reduced sampling schedule (seven data points) over 4 hours.
Main Results:
- The two-compartment model provided a statistically better fit to serum inulin disappearance curves compared to the one-compartment model.
- A minimum of seven data points (over 4 hours) was sufficient without significantly affecting model fit or calculated inulin clearance.
- The simplified 'seven-sample schedule' maintained clinical accuracy.
Conclusions:
- A standardized 'seven-sample schedule' combined with two-compartment analysis is a practical and accurate method for pediatric GFR determination.
- This optimized approach offers a balance between clinical accuracy and procedural convenience for inulin clearance measurements in children.
- The findings support the use of this refined method for routine GFR assessment in pediatric nephrology settings.
Abstract:
The total serum clearance of inulin after a single intravenous injection is an established method for the determination of the glomerular filtration rate (GFR). To optimize this procedure in children, we analyzed 117 serum inulin time-decay curves in 59 children (age range 1.3-15.2 years)with renal disease. It was found that the two-compartment model fitted statistically better to the disappearance curves of serum inulin than the one-compartment model. The sampling frequency could be reduced from 12 to a minimum of seven data points (t=0, 10, 20, 30, 65, 120 and 240 min) in 4 h without a relevant change in the fit of the two-compartment model to the date or in the calculated clearance of serum inulin. We conclude that, by using a standardized 'seven-sample schedule', followed by a two-compartment analysis, the single-injection serum clearance of inulin is a suitable compromise between practical convenience and clinical accuracy for the determination of the GFR in children.