Novel Saliva-based Renal Function Test Platform

Project Summary Chronic Kidney Disease (CKD) affects millions of people worldwide, including 20 million adults and children in the USA. Timely detection of kidney function deterioration can improve management of CKD, including in kidney transplanted recipients. Without a blood draw, an acute kidney injury (AKI) event or a transplant rejection could remain unrecognized for extended periods of time, leading to irreversible loss of kidney function and structure. Novel patient-friendly methods of kidney function measurement with high levels of precision and reproducibility are urgently needed to ensure more frequent and reliable monitoring in the home and for point-of-care screening. Currently, invasive phlebotomy followed by laborious blood specimen processing and reporting are the only way to measure the three major kidney filtration markers: serum creatinine, urea, and cystatin C. However, saliva has been proven to mirror blood biomarker levels. Limited preliminary data suggest that salivary creatinine and urea levels correlate with those in serum in CKD patients. Measurable levels of cystatin C have been assayed in saliva without being affected by periodontal disease. Based on these findings, Intelligent Optical Systems (IOS), in collaboration with the University of California (UC) Irvine and UC San Francisco, plans to develop (Phase I, 12 months) a novel means of detecting creatinine, cystatin C, and urea in saliva, using a highly sensitive and selective enzyme-based lateral flow assay (ELF assay). In this novel, compact, single-step, enzymatic multiplexed assay, highly fluorescent dyes yield reliable quantitative measurements on a portable analyzer. The innovatively developed methods will be subsequently (Fast-Track) validated in 200 CKD patients from UCI nephrology and transplant clinics (Phase II, 24 months). The proposed development builds on extensive IOS expertise in complex assay development, using saliva matrix that has been successfully validated in clinics for bone metabolism markers and rapid testing for drug of abuse. In Phase I we will demonstrate the feasibility of recording reproducible and sensitive measurements of salivary creatinine, cystatin C, and urea, using spiked and laboratory tested human saliva samples obtained from BioreclamationIVT. Assay specification, sensitivity LOD, specificity, and stability will be reported by the end of Phase I in accordance with IOS-established protocols for salivary assay development and optimization. Building on a successful Phase I demonstration of an ELF assay, and validating the results against the predetermined milestone criteria, we will then conduct the clinical validation in Phase II, testing saliva measurements against blood levels in 200 human subjects with CKD – including 50 kidney transplant recipients – with a broad range of GFR of 10-60 mL/min/1.73 m2 BSA. Our proposed Fast-Track design is efficient, feasible, and innovative, and has a high likelihood of sustained powerful influence and immediate clinical applicability. The availability of non-invasive, point-of-care, multiplex measures of kidney function would have a dramatic impact on the care and monitoring of patients with CKD, particularly in remote locations.Project Narrative Intelligent Optical Systems, in collaboration with the University of California Irvine Nephrology and transplant Centers, proposes to develop a novel rapid technique for measuring three kidney function markers in saliva. The device will be portable for rapid bedside measurement of saliva samples acquired noninvasively from patients in point-of-care and home settings, and for rapid screening. The multiplexed measurements of the target markers will not only be a reliable and reproducible measure of kidney filtration function, but will also be an early predictor of CKD progression or acute worsening of kidney function in transplanted patients.