Shining a Light on Saliva Testing
How biomarkers for oral and systemic disease can be identified from an easy- to-collect sample
Fred W. Michmershuizen
As new technologies come online, opportunities for improving patient care continue to expand. One of the most promising areas is the growing field of saliva testing. Like blood, a person's saliva contains biomarkers. But unlike blood, collecting saliva does not require a needle. Obtaining a sample is painless, and it can easily be done in a dental chair, in a mobile clinic, or at home. When scientifically analyzed, a saliva sample can point to risk factors not only for caries and oral disease, but for many different types of systemic conditions as well. These diagnostic clues can aid caregivers at all levels in detection, risk prevention, and treatment. As increased acceptance and economies of scale make saliva testing more widely available and affordable, the possibilities for the future are enough to make your mouth water.
Let's take a closer look at what can be learned by testing a patient's saliva.
Saliva is, of course, necessary for a person's health and wellbeing and has several functions, namely, to aid in the digestion of food, to protect against harmful infections, and to lubricate and protect teeth and gums. Most people never even think about their saliva during the course of the day, unless they don't have enough of it. An adequate secretion of saliva is necessary for optimal oral health. For patients with xerostomia, often associated with decreased saliva production, several methods of treatment are available.1 Assuming a patient produces a healthy amount of saliva, examining it can tell us a great deal about that person's oral and overall health.
Detecting Biomarkers in Saliva
The use of saliva as a diagnostic tool has been studied extensively.2 According to the American Dental Association (ADA), a wide range of biological components can be detected in saliva, including hormones, cytokines, antibodies, proteins and enzymes, metabolites and electrolytes, DNA and other nucleic acids, markers for tumors, prescribed and illicit drugs, and all types of microorganisms, including bacteria, viruses, and fungi.3 The American Academy for Oral Systemic Health (AAOSH), an organization dedicated to fostering awareness of the connection between oral and systemic health, has identified saliva testing as a helpful tool that can be offered in dental settings.4,5
Despite the advantages of saliva testing as a diagnostic tool, it has yet to become a standard everyday procedure for dental practices.6 That may change, however, as more companies enter the arena with proprietary testing mechanisms. Some of these tests involve sending a sample to a lab, while others offer rapid results. Many tests are designed to detect specific strains of bacteria that are associated with caries and periodontal disease. Others track factors such as pH, electrolytes, and glucose. There is testing geared specifically toward orthodontic patients and other testing intended for patients who are pregnant. Still other tests are being designed for screening wide swaths of people.
Laboratory testing of saliva and other oral fluids is regulated under federal standards established by the Clinical Laboratory Improvement Amendments (CLIA) of 1988, and these standards are designed to ensure that testing is reliable and accurate.3,7 According to the ADA's interpretation of the CLIA, for a test to make a claim of clinical validity it must receive authorization from the United States Food and Drug Administration (FDA), and as of June 2021 no saliva test has been approved by the FDA for evaluating risk of periodontal disease, dental caries, or head and neck cancer.3,7 This situation could change at any moment, as industry continues to innovate. Multiple tests have received emergency use authorization from the FDA to detect SARS CoV-2 (COVID-19) infection and antibodies in saliva and gingival crevicular fluid.3,8,9 There are also two oral fluid tests that have been authorized by the FDA to detect cancer risk.3,10
A lack of FDA authorization does not preclude dental professionals from utilizing saliva testing products, just from relying on them for making clinical decisions. Dental and healthcare professionals at all levels generally acknowledge that more information about what is happening inside a patient's mouth and body is better than less, and having measurable data can only improve the level of care.
Consider the periodontal probe, for example, which is not a diagnostic tool, but something that measures tissue damage that has already taken place due to inflammation.11 Salivary testing has the potential to detect risk factors, such as the presence of harmful bacterial strains associated with caries and periodontitis, so that action can be taken before disease can progress.
Maria L. Geisinger, DDS, MS, a professor in the Department of Periodontology at the University of Alabama at Birmingham, says "trust but verify" is a good mantra to keep in mind when evaluating a particular testing technology and whether it can be of use in clinical practice. "As tests become commercially available, look at what the research shows," Geisinger says. "Salivary analytics and other types of new diagnostic technology coming out is exciting, but we also have to look at the body of literature behind it to make sure that we're using these tools correctly."
Hygienists and dentists can benefit in several ways by offering saliva testing to their patients. These benefits include being better able to deliver improved outcomes, experiencing an increase in case acceptance, and, perhaps most helpful of all, having scientific findings to share with individual patients on risks for systemic conditions, such as diabetes, cardiovascular disease, dementia, cancer, and more.11
It's that third benefit, the ability to identify whole body health risks, that has the potential for the greatest impact. In many cases saliva testing might save a patient's life, literally. According to the ADA Health Policy Resources Center, 27 million people in the United States visit a dentist but not a physician each year.12 The potential impact of saliva testing is noticed, therefore, by those working in public health. "When you're in a health provider shortage area, a hygienist or dentist might be the only health professional of any kind a patient sees in a year, so looking at everything that's within your scope is vitally important," says Crystal Spring, BSDH, RDH, LAP. Spring, who runs a mobile nonprofit organization, Smiles Across Montana, that provides care for the underserved, says she's looking forward to the day when saliva testing can be used as a screening tool by mobile clinics to detect whole-body health risks. A barrier, Spring says, has been affordability of the tests.
What Saliva Testing Can and Cannot Do
While the term "salivary diagnostics" is used extensively, it's important to keep in mind that it's not possible to test someone's saliva and, for example, diagnose him or her with caries penetrating into dentin on tooth No. 14, or determine they have Stage III periodontitis, nor can a saliva test indicate cancer, or the development of type 2 diabetes. What testing can do, however, is provide screening tools for risk assessment. These tools can be useful in developing a more effective course of treatment, as well as making informed referrals to health care providers for systemic conditions.
Staying up to date on technologies like saliva testing is all part of delivering the very best care for patients.
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3. Department of Scientific Information, Evidence Synthesis & Translation Research, ADA Science & Research Institute, LLC. Salivary diagnostics. ADA website. https://www.ada.org/resources/research/science-and-research-institute/oral-health-topics/salivary-diagnostics. Updated July 19, 2021. Accessed April 20, 2023.
4. Nabors TW. Critical role of saliva testing in your practice. American Academy for Oral Systemic Health website. https://www.aaosh.org/core-curriculum-ce/critical-role-of-saliva-testing-in-your-practice. Published April 18, 2022. Accessed April 20, 2023.
5. Anderson C. 2022 saliva analysis: the new patient engagement tool. American Academy for Oral Systemic Health website. https://www.aaosh.org/connect/2022-saliva-analysis-the-new-patient-engagement-tool. Published February 1, 2022. Accessed April 20, 2023.
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7. Centers for Medicare & Medicaid Services. CLIA overview. CMS website. https://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Downloads/LDT-and-CLIA_FAQs.pdf. Updated October 22, 2013. Accessed April 20, 2023.
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9. Rao PV, Nair-Shaef D, Chen S, et al. Performance and utility of an oral fluid-based rapid point-of-care test for SARS-COV-2 antibody response following COVID-19 infection or vaccination [preprint]. medRxiv. 2021. doi:10.1101/2021.06.28.21259657.
10. US Food and Drug Administration. Direct-to-consumer tests. FDA website. https://www.fda.gov/medical-devices/in-vitro-diagnostics/direct-consumer-tests. Updated December 20, 2019. Accessed April 21, 2023.
11. Nabors TW. Explore the benefits of salivary testing through direct diagnostics. Compend Contin Educ Dent. 2022;43(5)304.
12. Vujicic M, Israelson H, Antoon J, et al. A profession in transition. J Am Dent Assoc. 2014;145(2)118-121.