Abstract: PO2388
Validation of Novel Cystatin C (CysC) Rapid Measurement Assay with Human Saliva
Session Information
- CKD: Insights from Recent Clinical Trials and Large Real-World Effectiveness Studies
November 04, 2021 | Location: On-Demand, Virtual Only
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2102 CKD (Non-Dialysis): Clinical, Outcomes, and Trials
Authors
- Beshay, Manal, Intelligent Optical Systems, Inc., Torrance, California, United States
- Nguyen, Trong, Intelligent Optical Systems, Inc., Torrance, California, United States
- Ortega, Maria, Intelligent Optical Systems, Inc., Torrance, California, United States
- Nguyen, Danh V., University of California Irvine, Irvine, California, United States
- Rhee, Connie, University of California Irvine, Irvine, California, United States
- Kalantar-Zadeh, Kamyar, University of California Irvine, Irvine, California, United States
Background
Rapid, frequent point-of-care (POC) monitoring of kidney filtration markers such as cystatin C (CysC) that does not require laborious blood specimen draws/processing can improve chronic kidney disease (CKD) patient outcomes and care. Saliva as a non-invasive biofluid for monitoring kidney function addresses a clinical need for rapid diagnostics in POC and home-based testing. Emerging data suggests CysC as a more reliable kidney filtration marker than creatinine because it is not affected by age, race, ethnicity, or body mass.
Methods
Our Enhanced Lateral Flow (ELF) immunoassays were validated against a commercial ELISA kit for quantitative measurement of CysC in 76 human healthy and CKD patient saliva samples. We applied Pearson correlation and Bland-Altman analysis to compare the two data sets, and assessed inter-assay repeatability by validating the coefficient of variation (CV) across measurements for the samples. Each sample was measured in triplicate (n=3) to obtain the CV value. The ELF assay was tested with 116 samples, and ELISA with 51 samples, due to limited resources.
Results
The ELF assay CysC assessment showed high correlation to the ELISA measurements, with Pearson r=0.78 (Fig. A). Bland-Altman analysis showed a minor bias of -0.017 mg/L between the two assays (Fig. B). Both assays demonstrated a <10% CV for most of the tests, with the ELF assay presenting a lower overall mean CV (6.5%) than the ELISA kit (7.2%) (Fig. C). Data from stability studies verified that the ELF assay maintains functionality at Day 510 when stored at room temperature.
Conclusion
We have demonstrated rapid measurement of CysC in human saliva with our novel ELF assay, with acceptable POC characteristics, and repeatability and reproducibility equivalent to ELISA. The ELF assay provided more accurate and faster results (<30 min. vs. 3 hr. for ELISA), and also demonstrated a longer shelf life (stable at 510 days at ambient vs. ELISA requirements for storage at -20°C with a 1 yr. expiration date). Future validation studies could lead to a saliva testing framework for kidney function markers, and a potential paradigm shift in the monitoring and care of CKD patients.
Funding
- NIDDK Support