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Secrets of saliva

Secrets of Saliva:

August 2007

by Will Sansom

A 64-year-old man enters his doctor’s office after not eating for days. He has persistent nausea, vomiting, low-grade fever and itching. His skin tone is yellow. Through a stethoscope, the doctor detects the sound of excess fluid in the abdomen. He believes he is looking at a classic case of the liver-destroying infection hepatitis C, but needs to confirm with a laboratory.

Currently, a doctor verifies the diagnosis by drawing blood and sending it to a central lab in another location, perhaps another city, where it is analyzed for hepatitis C antibodies, elevated liver enzymes and other markers. He may also perform a liver biopsy to reveal inflammation. The serology and other lab reports may take days to return from the central laboratory.

Now researchers at the Health Science Center’s Dental School are studying how to detect hepatitis C — and other diseases — without pricking the skin for a blood sample. In the case of some harder-to-diagnose cases of hepatitis C, liver biopsies could be prevented. The dental investigators are working with saliva-based diagnostic technology developed at The University of Texas at Austin and licensed to a private company, LabNow Inc. Saliva contains a number of antimicrobial proteins and is a first line of defense against oral diseases. It can also be connected to a host of disease states, as reflected by antibodies, proteins and hormones.

The Dental School was invited to conduct studies under a $6.1 million grant awarded to U.T. Austin by the National Institute of Dental and Craniofacial Research (NIDCR). The research program seeks to validate whether a "lab-on-a-chip" system can rapidly diagnose a number of disease states, including hepatitis C, oral cancer, recurrent heart attacks and asthma. The University of Kentucky and the University of Louisville also are participating.

"The most exciting thing about this project is the technology," said San Antonio lead investigator and salivary gland expert Chih-Ko Yeh, B.D.S., Ph.D., professor of dental diagnostic science at the Health Science Center. "In 10 to 15 years, or even sooner, we will have a product in doctors’ offices that will make it obsolete to send samples to centralized laboratories like we do today. This product should make it possible to read results in 15 to 20 minutes instead of waiting days, and it will be non-invasive — much more comfortable for patients."

  Lab-on-a-chip system
Lab-on-a-chip system: The test reactive area is a silicon chip less than half an inch square with dozens of tiny wells in the chip and beads of reagents. When saliva flows over it, the beads light up.
A disadvantage to using saliva, rather than blood, is that saliva does not necessarily reflect the composition of the blood serum. Dr. Yeh said the key is to decide what kind of disease states can be effectively diagnosed using saliva. The current research is designed to do that.

The proprietary prototype is based on nanotechnology and requires only a tiny bit of saliva, Dr. Yeh said. The test reaction area is a silicon chip less than half an inch square with dozens of wells in the chip and beads of reagents in the wells. The second component of the system is a tabletop, portable reader with a screen.

"Each bead is tagged with a substance that, when saliva flows over it, lights up in the reader," said co-investigator Spencer W. Redding, D.D.S., M.Ed., professor and chairman of the department of dental diagnostic science at the Health Science Center and occupant of the Castella Dental Chair in Aging Studies. "This technology has a lot of gee-whiz characteristics to it. This could have application for lab tests for anybody, including children and the homebound elderly."

The San Antonio researchers are confirming the system’s accuracy and reliability by first testing for hepatitis B antibodies, which are more pervasive than hepatitis C in humans. "Once this is done, we intend to confirm our data with detection of HIV antibodies, and then will expand to making diagnoses of hepatitis C," Dr. Yeh said.

He pointed out that readouts in field clinics in remote places, such as villages in Africa, could be sent via the Internet for other physicians to make diagnoses and suggest health care.

Excitement is sure to build as the project progresses, because the easier and faster that science can make the diagnosis of human diseases, the more often those diseases will be detected and treated for the betterment of individuals and the societies in which they live.


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