Practical approach for determining glomerular filtration rate by single-injection inulin clearance

Area of Science:

• Nephrology
• Biochemistry
• Medical Diagnostics

Background:

• Glomerular filtration rate (GFR) is a key indicator of kidney function.
• Accurate GFR measurement is crucial for diagnosing and managing kidney diseases.
• Current methods, like isotope clearance, can be complex and time-consuming.

Purpose of the Study:

• To evaluate a simplified single-injection inulin clearance method for GFR determination.
• To compare the accuracy of this new method against a standard isotope clearance technique.
• To assess the method's ability to detect early declines in GFR.

Main Methods:

• Compared single-injection inulin clearance with 99mTc-DTPA isotope clearance in 21 subjects (GFR > 35 mL/min).
• Administered a 5g inulin bolus, collecting blood samples at 20, 45, 90, 120, 145, 180, and 240 minutes.
• Measured inulin concentrations using sensitive chemical or enzymatic methods.
• Calculated GFR using a one-compartment model with inulin levels from two sampling times (20 and 240 min).

Main Results:

• The single-injection inulin method yielded GFR values comparable to the isotope technique (y = +4.80 mL/min + 0.92x, r = 0.97).
• Inulin concentrations at 20 and 240 minutes were sufficient for accurate GFR estimation.
• The method demonstrated potential for detecting early decreases in GFR in subjects with mild kidney impairment.

Conclusions:

• Single-injection inulin clearance, using only two blood samples, provides a reliable GFR measurement.
• This simplified method is suitable for clinical use and can aid in early detection of kidney damage.
• Further validation in broader patient populations is warranted.