Simple sampling strategy for measuring inulin renal clearance

Area of Science:

• Nephrology
• Renal Physiology
• Diagnostic Methods

Background:

• Standard inulin clearance (Cin) requires multiple samples over 2 hours.
• Minimizing sample collection is desirable for practical clinical application.
• This study evaluates the accuracy of reduced sampling for Cin determination.

Purpose of the Study:

• To assess the validity of inulin renal clearance using a single urine collection period of 30, 60, or 90 minutes.
• To determine the minimum collection time needed for accurate Cin measurement.
• To propose a simplified protocol for inulin clearance testing.

Main Methods:

• Utilized inulin clearance data from 737 individuals analyzed using the standard method.
• Calculated inulin clearance (Cin) with single urine collections of 30, 60, and 90 minutes.
• Analyzed serum inulin concentration changes and correlated results with standard Cin (Cin-ST).

Main Results:

• Serum inulin concentration showed minimal, variable changes during the clearance period.
• Single urine collections of 30, 60, and 90 minutes demonstrated high correlations with standard Cin (0.962-0.998).
• Root mean square errors decreased significantly with longer collection periods (10.4 to 2.3 ml/min/1.73 m²).

Conclusions:

• Inulin clearance with single urine collection is a convenient and accurate method.
• A single urine collection of 60 minutes offers a practical balance of convenience and accuracy.
• This simplified method supports efficient assessment of glomerular filtration rate (GFR).