Comparative Analysis of Glomerular Filtration Rate Measurement Techniques: Part 2. Current GFR Measurements.

Measured glomerular filtration rate (mGFR) remains the reference standard for precise assessment of kidney function when estimated approaches are insufficient. This second part of a two-part series reviews exogenous filtration markers used to obtain mGFR, including inulin, iothalamate, iohexol, and radionuclide-based tracers, with emphasis on their physiologic handling, analytic methods, accuracy, and clinical applicability. The review further examines emerging fluorescent and near-infrared tracers coupled with transcutaneous monitoring technologies that enable rapid or continuous assessment of GFR. Together, these approaches illustrate the evolution of mGFR measurement toward methods that are more practical, scalable, and responsive to dynamic changes in kidney function, while maintaining analytical accuracy.