Urine test could reduce need for blood samples

Photo: Female student shows sample in vial

Master's student Marissa Pierson holds a vial of proteins to be extracted for analysis; ©Clemson University

Researcher Ken Marcus and his students at Clemson University, South Carolina, have developed a new testing method that they believe will reduce costs, get faster results and lower the volume of urine needed for a sample than is the case with traditional testing methods.

It's great news for patients who get the willies when the nurse pulls out the needle to draw blood. The method Marcus and his students have developed could help make it possible to use urine instead of blood to test for more diseases.

Proteins in urine, for example, could help detect early signs of coronary heart disease, tell whether the body is rejecting a transplanted kidney and show whether someone has sleeping sickness. The trouble with testing urine is that it is awash in salt, Marcus said. It can be tricky to isolate the proteins that act as biomarkers. Those biomarkers are the clues that tell whether the patient is sick or has ingested a drug.

"You have got almost seawater coming out of you, and I am 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 ingredient in the group's research looks like kite string, but it is no ordinary twine. It is 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 a minute to wash off salt and other contaminants. Proteins are hydrophobic, so they remained stuck to the fibers. The researchers extracted the proteins by running a solvent through the tubes in the centrifuge for 30 seconds.

When it was all done, they were left with purified proteins that could be stored in a plastic vial and refrigerated until tested. The team was able to extract 12 samples in about five minutes, limited only by centrifuge capacity.

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 recently published by the journal Proteomics-Clinical Applications. The authors were Benjamin T. Manard, Sarah M.H. Jones and Marcus.

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, 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 free of contaminants as urine, he wrote.

The new method should also make it easier to test urine samples from babies, Marcus said. One of the challenges now is getting 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. They include W. Clay Davis, Dwella M. Nelson, Brad Knippel, Rayman D. Stannelle, Christine M. Straut, Tim M. Brewer, Jennifer J. Pittman, Manoj Randunu, Benjamin T. Manard, Carolyn Q. Burdette and Abby J. Schadock-Hewitt.

COMPAMED-tradefair.com; Source: Clemson University

More about Clemson University at: www.clemson.edu