Sample-to-Answer Quantitative Rapid Test for Point-of-Care Monitoring of Urinary Cystatin C Levels.

Urinary cystatin C (uCysC) has emerged as an endogenous biomarker for renal impairment. In managing renal pathologies, early screening and monitoring of disease progression are crucial for both at-risk individuals and diagnosed patients. The ultimate goal is to prevent and mitigate the associated risks of morbidity and mortality, thereby promoting longevity. However, conventional methods for quantifying uCysC have limitations that hinder their applications in point-of-care for resource-limited settings. In this study, we provide a sample-to-answer quantitative rapid test to monitor uCysC levels. The device uses a vent for urine sampling with a fixed volume, gravitational sedimentation for effective on-device reaction, and a dual-microbead immunoassay for the length-based visual quantification of uCysC. The achieved limit of detection (LOD) is 33.33 ng/mL, with excellent selectivity, pH level tolerance, and high accuracy. This all-in-one device bypasses peripheral lab settings to enable low-cost testing of renal impairment, which will benefit both general users and medical practitioners for telemedicine applications and large-scale disease self-management.