Scientists have analyzed calcium isotopes in patients' urine to determine early bone loss.

This technique was more sensitive in detecting bone loss than the X-ray method used today, with less risk to patients. Eventually, it could be used in clinical settings, and could be the beginning of additional innovative biosignatures to detect disease.

Scientists at Arizona State University (ASU; Phoenix, AZ, USA) and NASA are developing and applying the technique that originated in the Earth sciences. Using a model developed by ASU Professor, Joseph Skulan, scientists can compare the variously sized isotopes to determine whether patients' bone density is decreasing.

Bone deterioration can strike when a person experiences skeletal unloading--a result of bones not having to carry weight--and that is common in both hospital patients and astronauts. The scientists studied the urine of 12 healthy, but bed-ridden patients, finding that their method could detect bone loss after just a week of bed rest, much faster than the current method of X-ray absorptiometry.

The findings were published in the online Early Edition of the Proceedings of the National Academy of Sciences of the USA (PNAS) the week of May 28, 2012. With proof of concept in hand, the scientists hope to expand the method to detect bone-density changes in cancer patients. "We showed that the concept works as expected in healthy people in a well-defined experiment," said senior author Ariel Anbar. "The next step is to see if it works as expected in patients with bone-altering diseases. That would open the door to clinical applications."

With the new technique, bone loss is detected by carefully analyzing the isotopes of the chemical element calcium that are naturally present in urine. Patients do not need to ingest any artificial tracers and they are not exposed to any radiation, so there is virtually no risk, the authors noted.

The concept extends even beyond bone and calcium, the authors noted. Many diseases cause subtle changes in element isotope abundances, or in the concentrations of elements. These sorts of signatures have not been systematically explored in the development of biosignatures of cancers and other diseases.

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