Glomerular Filtration Rate Measurement Utilizing Transdermal Detection Methodology

The well-known accuracy limitations of estimated GFR (eGFR) currently employed in clinical practice present barriers to optimal care for patients with, or at-risk for, decreased kidney function. A point-of-care glomerular filtration rate (GFR) measurement methodology has the potential to address these limitations. We prospectively assessed transdermal detection of the novel fluorescent GFR tracer agent relmapirazin in participants having normal or impaired kidney function across all human skin colors on the Fitzpatrick Skin Scale (FSS). A multi-center study comprising 74 participants with eGFR from normal to Stage 4 CKD was performed. Forty-six participants were FSS types I-III, and twenty-eight were FSS type IV-VI. A module containing an LED and photodetector to activate and collect transdermal relmapirazin fluorescence was attached adhesively to the upper chest of each participant. Relmapirazin (1.5mg/kg) was administered by intravenous push, and fluorescence emission was acquired for 12 hours. A two-compartment pharmacokinetic model fit the fluorescent intensity vs time data, and the fluorescence clearance rate (FCR) was extracted from the second (terminal) compartment. Plasma relmapirazin concentrations were measured contemporaneously and the corresponding plasma GFR for each participant was determined. Linear regression analysis was used to compare the FCR to the indexed plasma GFR. Participant age range was 23 to 80 years old, with 59% females. The two-compartment pharmacokinetic behavior was observed in the fluorescence intensity vs time data and a FCR was successfully deduced for every participant completing the 12-hour study. The FCR vs. the indexed plasma GFR yielded an excellent correlation over the range of GFR measured and for all skin colors with a r2 = 0.90 (95% confidence interval 0.85 to 0.94). No severe adverse events were reported. Point-of-care transdermal detection of the fluorescent GFR tracer agent relmapirazin was feasible in patients with normal to impaired kidney function and for a range of skin color types.