In the past six years, saliva has risen to center stage for disease detection, monitoring and even health surveillance. A number of foundational research tools are now in place to fully explore the clinical utilities and potentials of saliva including oral cancer screening and detection. DTI in cooperation with FDI Worldental Daily spoke with Dr David Wong, USA, at this year's World Dental Congress in Singapore about the value of salivary biomarkers for identifying systemic diseases.

Worldental Daily: In recent years, the role of saliva for the detection and monitoring of diseases has risen to centre stage. Can you summarise the latest findings for us?
Dr David Wong: Seven years ago, the National Institute of Dental & Craniofacial Research (NIDCR), one of the 27 institutes at the US National Institute of Health (NIH) made a visionary investment to turn salivary diagnostics into a clinical reality. The outcomes of this scientific investment are what constitute the recent excitement and clinical potentials for salivary diagnostics. We now know there are multiple diagnostic alphabets in saliva to define the diagnostic coordinates of oral and systemic diseases. Point-of-care diagnostic technologies are soon to be in place to permit a drop of saliva to detect and monitor diseases at the dentist office.

We all know what saliva is made of as well as about its several functions in the mouth. How exactly does it work as a biomarker?
Biomarkers are defined as cellular, biochemical, and molecular characteristics by which normal and/or abnormal processes can be recognised and/or monitored. On a daily basis, the salivary glands (major and minor) secretes ~1.5 litres of saliva into the oral cavity, carrying with it health/disease information biomarker information. The sources of these biomarkers can be from disease sites or the salivary glands themselves can produce disease informative surrogate biomarkers. The salivary gland system can be perceived as a local anatomical organ that is poised to monitor local and systemic diseases. The real blessing is that they secrete a biofluid, saliva, that can be obtained non-invasively, non-painfully, non-embarrassingly without needles and cringing.

What salivary diagnostic toolboxes are at hand or currently in development? How may one be able to incorporate it into one’s clinical practice? Are they Food and Drug Administration (FDA)-approved?
Current salivary diagnostic toolboxes include the diagnostic alphabets (proteome, transcriptome, micro-RNA and microbial) and point-of-care diagnostic technologies. Integration into clinical practice requires identification of impactful clinical application and approval by the FDA. With the exception of the salivary HIV antibody test, no other salivary biomarker test has reached the FDA-level evaluation. We anticipate our point-of-care device and biomarkers for oral cancer detection to be evaluated by the FDA in two years.

What is their diagnostic value? Is it possible, for example, to detect early stages of oral cancer through these toolboxes?
Using the salivary biomarker technologies developed at University of California Los Angeles, we were able to harness clinically robust and highly discriminatory salivary biomarkers (> 90 per cent sensitivity and specificity) that can detect early state of oral cancer and Sjögren’s syndrome patients.

What about systemic and psychobiological diseases?
The value of salivary biomarkers for systemic disease is one of the final frontiers. It is the Holy Grail. Intense research is ongoing in my lab and others. It will be safe to predict that definitive clinical and basic science data will be available in the next 24 months to substantiate beyond any doubt that systemic diseases, including neurological disorders, will be reflected diagnostically in saliva. Using animal models we have already published work to demonstrate the systemic disease salivary biomarker connection.

What are the limits of saliva diagnostic toolboxes?
The limits and boundaries of salivary diagnostic toolboxes constitute the scientific values of these endeavours. For example, with the limits and boundaries of the salivary proteome determined, 1166 proteins, we now know the resolution of saliva for clinical diagnostic applications based on the proteome alphabet. Knowing these limits defined the scientific foundation and credibility of saliva as a clinical entity. The existence of multiple diagnostic alphabets in saliva (proteome, transcriptome, micro-RNA and microbial) and their associated defined contents elevate saliva as a top tier contender for personalised individual medicine applications, in addition to clinical diagnostics.

Do oral diseases have any impact on the diagnostic value of saliva?
A number of oral diseases have been evaluated for salivary diagnostic applications including caries assessment, oral cancer, and periodontal disease. Proper control of oral diseases in the study population to control the effect of periodontal disease and inflammation in particular is important.

Thank you very much.

(This interview is published with permission by the FDI World Dental Federation.)