A new method of mapping human saliva may represent a breakthrough in diagnosing dozens of ailments.

Dr. David Wong, associate dean of research at California's UCLA school of dentistry, has identified the key protein and genetic compounds that comprise saliva.

Scientists expect the development to allow the early detection of diseases from lung cancer to osteoporosis because the composition of saliva changes when a disease is present.

Wong's research could mean that blood tests are no longer necessary for many types of tests. Patients could simply be asked to spit in a test tube, providing the sample fluid necessary for the test.

"If parts of our bodies are not happy and are going through stages of disease, they (the salivary glands) know about it," Wong told the Toronto Star.

"They will change their physiology and biochemistry."

Wong will present his findings today at the International Association of Dental Research in New Orleans.

He says scientists have managed to map all 1,500 proteins in healthy human saliva. They have also come up with a complete listing of the 1.4 million pieces of genetic information contained in saliva and known as the genome.

"We have known for decades that there is information in saliva that is good for disease detection except we could never put our hands on it," Wong said. "The technology wasn't there to turn it into clinical utility."

That technology has been developed over the past four years with the help of a US$85 million grant from the U.S. National Institutes of Health.

The cataloguing process is now complete, and scientists expect to be able to diagnose disease from specific changes in saliva composition.

"Knowing these alphabets we can basically find out what the saliva-specific signature is for heart disease, for osteoporosis, for neurological disorders and for cancers," said Wong.

Tests for specific diseases, such as lung cancer, should be available within several years, Dr. Wong said.

Scientists at the University of Texas Dental Branch at Houston have also been working on saliva analysis, and say they have developed a test that may assist in the diagnosis, treatment and follow-up care of breast cancer.

The Texas researchers warn that the saliva test would only be one of a number of testing procedures for breast cancer, and wouldn't eliminate the need for regular mammogram screening or blood testing.

The test has not yet been approved by the U.S. Food and Drug Administration.

The human circulatory system connects the salivary glands to every organ in the body, which creates 1.25 litres of saliva every day through three pairs of salivary glands.