A simple spot test promises to improve the detection of urinary proteins that can indicate renal problems and kidney failure. Japanese researchers have developed a point-of-care test which potentially poses a big improvement over current testing methods with its high sensitivity and short analysis times. 

Elevated levels of proteins, such as human serum albumin (HSA), in urine indicate kidney problems, which is a widespread public health concern. Until now, no methods for simple yet sensitive detection existed as most screening methods require sophisticated instrumentation. The test developed by Emiko Kaneko and colleagues at Tokohu University, Sendai uses a dye to visualise HSA proteins in urine. 'It is well recognised that the anionic dye (Erythrosin B) binds to a protein molecule through electrostatic and hydrophobic interactions,' explains Kaneko. 

The urine sample, dye and polyethyleneglycol (Peg) are mixed and a drop placed on a membrane-based test strip. The dye binds with HSA resulting in a change in its absorbance causing the drop to produce a pink-red ring on the test strip. As well as the results being visible to the naked eye, further measurement of the dye's absorbance using a spectrometer allows for sensitive detection of the protein levels in the sample. The use of Peg in the test is key feature as it increases the sensitivity by maintaining good dispersion of the dye, says Kaneko. 

The simplicity of the test means that it could be developed for daily monitoring in patients. Cristina Davis an expert in biosensors at the University of California says that 'easy to use and cost-effective point-of-care diagnostic tests such as this are extremely promising, and should provide important information for clinicians managing patient care.' 

Looking to the future, Kaneko and his coworkers are keen to commercialise the test and have already begun a clinical surveillance study using both patients and healthy subjects. 

David Sharpe 

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