Accuracy of Point-of-Care Transdermal GFR Methodology

Background Chronic kidney disease (CKD) is typically staged using population-derived empirical equations to estimate GFR (eGFR) based on serum creatinine and/or Cystatin C. However, these eGFR equations can be inaccurate for an individual patient. While plasma-derived GFR using an exogenous agent is the preferred methodology, the requirement for multiple blood samples and laboratory analysis limits its clinical practical utility. We have shown the fluorescent molecule relmapirazin is an exogenous GFR tracer agent and its transdermal fluorescence detection at the point-of-care can assess a clinically relevant range of GFR across all human skin colors. In the current study, transdermal GFR (tGFR) was compared to the plasma-derived indexed GFR (nGFR) in a multi-center pivotal clinical study. Methods We evaluated 182 participants with normal eGFR to CKD Stage 4 across all six Fitzpatrick Skin Scale (FSS) types. A sensor attached to the chest contained an LED and photodetector for transdermal fluorescence detection following intravenous administration of relmapirazin. The primary endpoint was percentage of tGFR values within 30% of nGFR (P 30 ). Results P 30 of 94% (95%CI 89-97%) was obtained for the entire cohort. P 30 was 96% and 92% for participants with GFR greater than or less than 60 mL/min/1.73m 2 , respectively. P 30 of 96% was for participants with FSS I-III and 90% with IV-VI. Conclusion The tGFR yielded a higher P 30 value than creatinine-based eGFR equations reported in the current literature. For the cohort subsets of CKD strata and FSS, all P 30 values observed were in the optimal range as established by the 2024 KDIGO guideline.