New urine testing method to improve disease detection

Researchers from Clemson University have developed a new urine testing method that is said to reduce costs, achieve faster results, lower the volume of fluid needed and remove the need for invasive blood tests.

Professor Ken Marcus explained that the problem with testing urine is that it’s awash in salt, meaning it can be tricky to isolate the proteins that act as biomarkers - the clues that tell whether the patient is sick or has ingested a drug.

“You’ve got almost seawater coming out of you, and I’m trying to find something far smaller than a needle in a haystack,” Professor Marcus said. “The concentrations of these proteins would be one part in a billion.”

In a study published in the journal Proteomics - Clinical Applications, Professor Marcus and his students added capillary-channelled polymer fibres - which look a bit like kite string - to micropipette tips. They then passed urine samples through the tubes by spinning them in a centrifuge for 30 seconds, before running de-ionised water through the tubes to wash off salt and other contaminants.

Proteins are hydrophobic, so they remained stuck to the fibres. The team extracted the proteins by running a solvent through the tubes in the centrifuge for 30 seconds. The researchers were left with purified proteins that could be stored in a plastic vial and refrigerated until it was time for testing.

The team was able to extract 12 samples in about five minutes, limited only by centrifuge capacity. Compared to polymer beads, which are used to extract proteins in current urine tests, the fibres are described by Professor Marcus as “smaller, faster and cheaper”. The new method also requires only a few microlitres of urine, which should make it easier to test urine samples from babies.

In a review of the article, Professor Youhe Gao of Beijing Normal University wrote that the method “may have more profound implications than the authors have claimed”, with urine having the potential to act as a better biomarker source than blood.

This is because various mechanisms in the body limit changes in the blood, whereas urine “accumulates all kinds of changes”, Gao said. He added that urine is the mostly easily obtained bodily fluid apart from sweat, which may not be as informative and free of contaminants as urine.

“Urine is more important than most biomarker researchers realise,” Gao wrote.

Image caption: Master’s student Marissa Pierson holds a vial of proteins to be extracted for analysis.

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