Rapid, Precise, and Clinically Relevant Quantification of Urinary Albumin and Creatinine Using a NanoDrop UV-Vis Spectrophotometer

Albuminuria is a sensitive biomarker of kidney dysfunction, and the Albumin/Creatinine Ratio (ACR) is an essential measure for monitoring diabetic kidney disease (DKD). Abnormal levels can indicate a propensity for progressive renal failure and other complications such as cardiovascular diseases. This study employed UV/Visible spectroscopy to analyse aqueous urine samples spiked with bovine serum albumin (BSA) and creatinine at clinically relevant concentrations (0-30 mg/L for albumin and 600-1800 mg/L for creatinine).

UV/Visible spectra of co-spiked samples recorded in triplicate revealed distinct bands at 229 nm and 249 nm, corresponding to BSA and creatinine, respectively, alongside other amino acid bands. Partial Least Squares Regression (PLS-R) analysis for BSA yielded Root Mean Square Error of Calibration (RMSEC) and Cross-Validation (RMSECV) values of 66.93 and 73.92 mg/L, respectively. For creatinine, RMSEC and RMSECV values were 244.32 and 275.65 mg/L, respectively. Prediction models for both BSA and creatinine compared to ELISA demonstrated robust performance with R²PRED values of 0.96 and 0.95, respectively, indicating strong model reliability. The Limit of Detection (LOD) for co-spiked samples was 19.82 mg/L for BSA and 58.43 mg/L for creatinine. Our Univariate anlaysis of BSA bands at 230 nm and 287 nm produced a R2 of 0.984 for both and LOD values of 0.136 mg/L and 0.115 mg/L respectively.

These results demonstrate proof of concept of applying UV/Visible spectroscopy-based method as a rapid, cost-effective point-of-care (PoC) tool for ACR measurement, offering promising applications in the early diagnosis, monitoring, and prognosis of diabetic kidney disease and associated cardiovascular complications. The next stage will involve a clinical trial to evaluate the technology's potential under real-world conditions.