Lab Chip 13, 4231–4238 (2013)

Monitoring the albumin levels in urine can be used to diagnose the early stages of kidney diseases, a growing global health problem. Because albumin levels fluctuate with time, tests should ideally be performed every few hours, but this demands successive patient visits to clinics. Now, Ahmet Coskun and colleagues from the University of California in Los Angeles, USA, have developed a lightweight, compact photonic attachment for a smart phone that can be used to measure albumin levels from urine samples. It uses a diode laser to simultaneously excite fluorescence in test and control samples. The fluorescence from both samples is then imaged using a lens and the existing camera unit on the smart phone. The tests take about 5 min to perform. Using buffer and synthetic urine samples, the researchers demonstrated that the platform has a detection limit of 5–10 μg ml−1, which is over three times better than the clinically accepted normal range of ≤30 μg ml−1. The researchers claim that the tester could be extended to enable simultaneous testing of multiple compounds, enhancing its usefulness for early detection of kidney-related diseases.