Validation of New Markers of Glomerular Filtration Rate: Dota Gadolinium and Calcium EDTA (MultiGFR)

Research on estimation and measurement of renal function has been greatly stimulated by the international concept of chronic kidney disease (CKD) and its classification into stages of severity based on the level of glomerular filtration rate (GFR) (National Kidney Foundation KDOQI and ANAES in 2002, KDIGO conference in 2005), and by the development of recommendations for clinical practice according to this stages. Many efforts have focused on the validation of new formula to estimate GFR from endogenous markers. Nevertheless, the performance of these formula is limited by a large inter individual variability, that requires in many cases the use of GFR measurement using exogenous tracers (extreme anthropometric characteristics, abnormal production of endogenous tracers, potential kidney donors, dose adjustment, nephrotoxicity monitoring…). The use of GFR measurement is burdened by a lack of availability due to methodological, biological and regulatory (for radioactive tracers) constraints. That's why a need exists for new validated tracers that will be more accessible and easier to use. Moreover, there are differences between the measurement techniques: single injection of the tracer or concentration equilibrium obtained by continuous infusion; plasma or urinary clearance. Two new tracers for GFR measurement are here offered for validation: Gd-DOTA and Calcium-EDTA. Gd-DOTA is a macrocyclic paramagnetic contrast product, which can be measured using an ELISA type immunoassay. Although being widely used in radiology with higher doses than those that will be used for GFR measurement in the multi-GFR study, Gd-DOTA has never been involved in systemic nephrogenic fibrosis cases (ProFinest study). Calcium-EDTA has been used for many years for the chelation of heavy metals. Recently, a colorimetric assay for Calcium-EDTA measurement has been developed. Gd-DOTA and Calcium-EDTA clearance for GFR measurement will be compared to inuline clearance in healthy volunteers (25 for each new tracer) and CKD patients (150 for each new tracer).