Measured Glomerular Filtration Rate: The Query for a Workable Golden Standard Technique

Area of Science:

• Nephrology
• Clinical Chemistry
• Biomarker Discovery

Background:

• Inulin clearance was the reference for measured glomerular filtration rate (mGFR), but limitations exist.
• Serum creatinine has known limitations; exogenous markers like iohexol, iothalamate, and radioisotopes (e.g., 51Cr-EDTA) are used for accurate GFR estimation.
• Lack of standardization in exogenous marker assays and protocols leads to variability in mGFR results.

Purpose of the Study:

• To highlight the need for standardization of measured glomerular filtration rate (mGFR) methods.
• To address the scientific and regulatory challenges hindering the clinical use of current mGFR techniques.
• To advocate for the development of reliable endogenous filtration markers for accurate GFR estimation.

Main Methods:

• Review of existing literature on exogenous filtration markers for GFR measurement.
• Analysis of limitations associated with inulin, serum creatinine, and various exogenous markers (radioactive and non-radioactive).
• Discussion of challenges including lack of certified reference materials, standardized protocols, and regulatory hurdles.

Main Results:

• Current exogenous mGFR methods (iohexol, iothalamate, radioisotopes) lack standardization in markers, analytical techniques, and procedural protocols.
• Significant variations in reported mGFR results question the reliability of these methods as a gold standard.
• Regulatory issues further restrict the clinical application of existing mGFR techniques.

Conclusions:

• Standardization of the filtration marker, analytical method, and GFR determination procedure is urgently required for mGFR.
• Development of an endogenous filtration marker or panel for single-blood-draw GFR estimation, comparable in accuracy to mGFR, is needed.
• Standardization will enhance the scientific reliability and clinical utility of kidney function assessment.