Automated colorimetric gadolinium assay for verification of clearance and estimation of glomerular filtration rate.

Background: NSF (nephrogenic systemic fibrosis) is a potentially serious adverse effect for renal patients undergoing MRI (magnetic resonance imaging) procedures using gadolinium-containing contrast agents. There is therefore a need to verify clearance of these agents and to confirm appropriate renal status of patients treated with these drugs.

Methods: Serum samples from canine and feline subjects dosed with 0.1 mmol/kg of gadolinium agent, or from spiked samples were assayed for gadopentetate (Magnevist), gadodiamide (Omniscan) or gadoversetamide (OptiMARK) using a new dye reagent on the Olympus AU400. Accuracy was verified by ICP-MS.

Results: The reportable dynamic range is 3-600 micromol/l Gd. Split serum samples from animals dosed with 0.1 mmol/kg of gadopentetate ranged from 7-458 micromol/l Gd: y=1.121x+0.267, r=0.996, for the Olympus method as a function of Gd measurement by ICP-MS. Between-day imprecision was 1.3% CV-3.6% CV for samples ranging from 12-400 micromol/l Gd.

Conclusions: The assay is useful to verify the clearance of gadolinium and for evaluation of renal status by estimation of GFR using gadopentetate.