Validity of simplified protocols to estimate glomerular filtration rate using iohexol clearance

Area of Science:

• Nephrology
• Clinical Chemistry
• Pharmacokinetics

Background:

• Iohexol clearance is a precise marker for glomerular filtration rate (GFR).
• Current protocols for iohexol clearance are often lengthy and require multiple blood samples.
• Simpler, shorter protocols are needed for practical clinical application.

Purpose of the Study:

• To evaluate the feasibility of a simplified iohexol clearance protocol for estimating GFR.
• To determine if a single blood sample can accurately measure GFR using iohexol.
• To assess the clinical utility of a shortened protocol for routine GFR assessment.

Main Methods:

• Two iohexol clearance estimates were performed two weeks apart in 11 healthy individuals and 26 patients with chronic kidney disease (CKD stages 1-3).
• Blood samples were collected at 60, 90, 120, 150, 180, and 240 minutes post-iohexol injection.
• Iohexol concentrations in blood specimens were analyzed to calculate GFR.

Main Results:

• Excellent correlation was observed between the two visits (slope 1.00).
• Single-point estimates from 120 to 240 minutes showed coefficients of variation (CV) of 4.5-7.0%, comparable to the 240-minute reference method (5.4%).
• Multi-point estimates (2-3 samples between 60-120 min) offered no advantage and overestimated GFR at lower levels.

Conclusions:

• A single blood sample for iohexol clearance, collected 2 to 4 hours post-infusion, provides an accurate GFR estimate.
• This simplified method is a potentially suitable tool for routine clinical GFR measurement.
• Shortened protocols enhance the practicality of using iohexol clearance in clinical settings.