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New Urine Test Could Reduce Need for Blood Samples

Researchers look for biomarker concentrations as small as one part in a billion

Professor Ken Marcus and his students at Clemson University in South Carolina have developed a new testing method that could make it possible to use urine instead of blood to test for diseases. Proteins in urine, for example, could help detect early signs of coronary heart disease, tell whether the body is rejecting a transplanted kidney, or show whether someone has sleeping sickness.

The investigators believe that the new approach will reduce costs, provide faster results, and lower the volume of urine needed for a sample.

The trouble with testing urine, however, is that it’s awash in salt, Marcus said. Therefore, it can be tricky to isolate the biomarkers (proteins) that tell whether a 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,” Marcus said. “The concentrations of these proteins would be one part in a billion.”

The magic component in the group’s research looks like kite string, but it’s no ordinary twine. It’s made of capillary-channeled polymer fibers.

As part of a study, Marcus and his students packed the fibers into plastic tubes and then passed urine samples through the tubes by spinning them in a centrifuge for 30 seconds. Then the researchers ran de-ionized water through the tubes for 1 minute to wash off salt and other contaminants.

Proteins are hydrophobic, so they remained stuck to the fibers. Marcus and his students extracted the proteins by running a solvent through the tubes in the centrifuge for an additional 30 seconds.

When it was all done, 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 approximately 5 minutes, limited only by the capacity of their centrifuge.

In urine tests commonly used now, polymer beads extract the proteins.

“The difference is that ours is smaller, faster, and cheaper,” Marcus said.

The team’s work was published in Proteomics: Clinical Applications.

In a review of the article, Professor You-he Gao of Beijing Normal University wrote that the method “may have more profound implications than the authors have claimed, simply because urine is more important than most biomarker researchers realize.”

Various mechanisms in the body limit changes in the blood. Urine, however, “accumulates all kinds of changes and should be a better biomarker source than blood,” Gao wrote.

Further, urine is the mostly easily obtained bodily fluid, he wrote. Sweat can also be obtained noninvasively, but it may not be as informative and as free of contaminants as urine, according to Gao.

The new method should also make it easier to test urine samples from babies, Marcus said. One of the challenges is obtaining a large-enough sample, but the new method requires only a few microliters of urine.

The research has been about a decade in the making, with various students working on it over the years.

Source: Clemson University; May 25, 2015.

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