# Performance of Colorimetric Lateral Flow Immunoassays for Renal Function Evaluation with Human Serum Cystatin C

## TL;DR

This study evaluates a new colorimetric lateral flow immunoassay for detecting Cystatin C, a biomarker for kidney function, showing promising agreement with standard lab tests.

## Contribution

The study introduces a non-fluorescent lateral flow immunoassay for Cystatin C with optimized design and validation against a clinical standard.

## Key findings

- The developed LFIAs showed a 0.51 mg/L lower measurement compared to Roche assays.
- The 95% confidence interval ranged from 0.24 mg/L below to 1.27 mg/L above LFIAs’ results.
- The LFIA can detect early-stage renal impairment despite increased bias at low CysC concentrations.

## Abstract

Chronic kidney disease (CKD) is associated with heart failure and neurological disorders. Therefore, point-of-care (POC) detection of CKD is essential, allowing disease monitoring from home and alleviating healthcare professionals’ workload. Lateral flow immunoassays (LFIAs) facilitate POC testing for a renal function biomarker, serum Cystatin C (CysC). LF devices were fabricated and optimised by varying the diluted sample volume, the nitrocellulose (NC) membrane, bed volume, AuNPs’ OD value and volume, and assay formats of partial or full LF systems. Notably, 310 samples were analysed to satisfy the minimum sample size for statistical calculations. This allowed for a comparison between the LFIAs’ results and the general Roche standard assay results from the Southern Health and Social Care Trust. Bland–Altman plots indicated the LFIAs measured 0.51 mg/L lower than the Roche assays. With the 95% confidence interval, the Roche method might be 0.24 mg/L below the LFIAs’ results or 1.27 mg/L above the LFIAs’ results. In summary, the developed non-fluorescent LFIAs could detect clinical CysC values in agreement with Roche assays. Even though the developed LFIA had an increased bias in low CysC concentration (below 2 mg/L) detection, the developed LFIA can still alert patients at the early stages of renal function impairment.