Saliva: Surprising Applications in Medical Research

When you hear the word "saliva," several but common things will appear in your mind. One is the natural revulsion from picturing spits coming out of people's mouths. Another one is the ability to help digest and degrade starch into sugars via an enzyme known as amylase. And perhaps, you may have also heard that saliva is a nice little home for about 600 species of bacteria.¹ But, did you hear about this frivolous-looking liquid known as saliva contains proteins and RNA molecules? Furthermore, saliva's importance in medical research may be on the rise because of its wide availabilities and easy accessibility.

In an article written by Professor David T. Wong of UCLA, several interesting and surprising applications of saliva in medical research, including some that he and his colleagues conducted, were discussed.² Wong began this article by demonstrating the importance of this study. By using saliva as the material to conduct tests, two momentous issues in current health care were answered: safety and cost. In contrast to blood, saliva is much cheaper to obtain and does not have the risk of blood-borne diseases for people who carry out those tests.

So, let's hit the basics first - where does exactly saliva comes from?

Saliva originates from three types of salivary glands - sublingual gland, submandibular gland, and parotid gland. In the picture accompanying this article, number one corresponds to parotid gland, two to submandibular gland, and three to sublingual gland. Salivary glands are examples of exocrine glands, which "empty their secretions into ducts through which the secretions flow to points of release."³

Now, going back to Wong's article, he pointed out that a product named OraQuick was approved by U.S. Food and Drug Administration to detect HIV-1 or HIV-2 infection by using oral fluids. Although oral fluids are a bit different from saliva, they nevertheless hint the importance of saliva for detecting diseases. The manufacturer clinical studies reported that OraQuick correctly identified 99.3% of people infected with HIV and 99.8% of people without HIV.⁴ It did recommend confirmations from additional tests to confirm the results, however.

Still, for those people who cannot afford such tests (which, as we all know, may likely become more and more expensive) to determine whether they are infected with HIV viruses, these approved new tests will significantly reduce the burden and fear of having to go through long and expensive tests.

Wong personally conducted researches with his colleagues to experiment genetic materials in saliva on detecting several disease, including oral cancer and Sjögren's Syndrome, an autosome disease. Wong was interested in trying to detect early-stage oral cancer by using saliva, and his detailed study is available by PubMed here. Similarly, if you are interested in how Sjögren's Syndrome may be able to be detected using saliva, Wong published an article available here, and for more information on this syndrome, Mayo Clinic has a very detailed explanation on its website. I highly recommend you to check out these articles, but I will note that the articles by PubMed require subscription to see full text instead of just abstracts.

Bibliography

¹ Elizabeth Landau, "Spit happens: Saliva's mysteries revealed," CNN Health, 3 Mar. 2009, 28 May 2010 http://www.cnn.com/2009/HEALTH/03/03/saliva.spit.survey/>

² David T. Wong, "Salivary Diagnostics," American Scientist January-February 2008 Vol. 96, No. 1.

³ Richard W. Hill, et al., Animal Physiology (Sunderland: Sinauer Associates, Inc., 2004) 261.

⁴ Department of Health and Human Services: Centers for Disease Control and Prevention, "OraQuick Rapid HIV Test for Oral Fluid - Frequently Asked Questions." Centers for Disease Control and Prevention," 19 October 2006 (latest modified), 28 May 2010 (accessed) http://www.cdc.gov/hiv/topics/testing/resources/qa/oralfluidqandafin.htm>