A simple saliva test might soon replace blood and urine testing as the standard method for detecting disease or drug abuse. A team of American researchers made that prediction at the recent meeting of the American Association for the Advancement of Science in Washington. The spit test relies on a variety of emerging medical technologies.
Researchers have known for a long time that human spit - saliva -- is a lot like blood. It contains enzymes, hormones, antibodies and bits of genetic material. Oral tests for HIV, alcohol and steroids, among other drugs, are already in use in the United States and other countries.
But, now spit is moving into the mainstream as a diagnostic tool. Scientists applaud its virtues. Saliva is always available, and samples can be collected easily, without using invasive needles or having to wait on a patient's bladder.
Biochemist Daniel Malamud says the saliva test he is developing at the University of Pennsylvania can detect certain microbes like HIV and a harmless bacterium related to anthrax.
He is working on the prototype for an oral swab kit. The device - about the size of a credit card - could analyze samples on the spot in emergency situations or in a doctor's office to test, for example, for common respiratory infections in children.
"(So, for example) You take your kid to the doctor. He looks in the mouth and says, it is probably a virus, but just to be safe, he says, 'I'll put you on an antibiotic. Call me in 48 hours. I'll give you the results from the strep test.' And then he will say, 'It was strep negative, but you may as well stay on the antibiotics.' The patient doesn't. So, if we could take an oral sample and before the person has left the emergency room or the doctor's office you can tell them what it is that they have."
Such information would reduce the misuse of antibiotics, which can lead to drug resistant bacteria. Saliva has also been the focus of Paul Denny's research. He's a professor of diagnostic sciences at the University of Southern California.
His research shows a relationship between saliva proteins and tooth decay. He says the test can predict in children the timing and number of cavities and which teeth are most vulnerable.
"There is also a version of the test that we have been able to develop in which we can forecast deciduous teeth, that is the baby teeth, and this leads us to the possibility that eventually a version of the test would be included in a well baby checkup to provide to provide early information on what the future health care needs of that child might be."
Saliva tests may also provide early screening for oral cancer and other systemic diseases. New findings from the University of California Los Angeles show that genetic molecules in saliva match oral cancer proteins with 91 percent accuracy.
Scientists like David Wong with the UCLA research group says the work comparing saliva proteins of healthy people with those of people with disease is advancing diagnostic research and could help improve survival rates.
"We must first identify what are the usual proteins in people like ourselves in normal saliva and then we can begin to look at disease populations and see if they have signatures, protein signatures such as diabetes, cancer, rheumatoid arthritis and so on and so forth.
David Wong says that such early detection of disease saves lives, lowers medical costs and promotes lifetime wellness. The National Institute of Dental and Craniofacial Research - an agency within the National Institutes of Health - is funding multiple projects across the United States to bring diagnostic saliva tests to market within two or three years.