The combination of patient preference for nonpainful, minimally invasive testing options and recognition that the convenience of rapid, point-of-care testing may facilitate earlier diagnosis of many chronic conditions is driving the push toward clinical adoption of saliva-based diagnostics tests.

“Noninvasive could be defined as something that sits on the skin and takes a measurement from the body without a sample, like continuous glucose meters,” says James Nichols, Ph.D., director of clinical chemistry at Baystate Medical Center (Springfield, Mass.). “Saliva and urine testing, I might call minimally invasive.”

Why the interest in noninvasive testing in general? “It is not a cost issue so much as a convenience and privacy issue,” says Nichols, who cautions that the technology will improve in the near term to the point that clinical adoption may be more pervasive. “There is still concern on the lab side about the technical performance. Are they as precise and accurate as a central lab? Are we getting as reliable results? That question is not fully resolved yet, but it will clearly continue to advance in the next five years.”

Increasing Scientific Attention
Oral fluids-based diagnostic testing has emerged as a translational and clinical priority with national visibility. Detecting dozens of diseases in a sample of saliva was issued by President Obama as one of the 14 “Grand Challenges” for biomedical research in the 21st century. In order for the scientific community to achieve this, the National Institutes of Health’s National Institute of Dental and Craniofacial Research (NIDCR) has invested heavily over the past 10 years in research efforts to substantiate the scientific foundation of salivary diagnostics and to begin to determine which conditions might be correlated with biomarkers found in saliva.

Initial research focused on developing the “diagnostic alphabet” of saliva by first defining and cataloging all the proteins and RNAs present in saliva and at what resolution. To date 1,166 proteins have been identified and represent the foundational toolbox for building clinical diagnostic applications. To disseminate these findings and foster translational efforts, the Salivaomics Knowledge Base, an online database, was developed, and by using bioinformatics applications, saliva proteins can be matched to existing research efforts demonstrating the protein’s function elsewhere in the body. In the last few years, researchers from University of California Los Angeles (UCLA) have applied this research tool and discovered they can diagnose early-stage oral cancer and the autoimmune disease Sjögren’s Syndrome from saliva.

NIDCR also called for the development of point-of-care biosensor technologies that will permit the use of a drop of saliva for the simultaneous detection of multiple salivary biomarkers in real time and in a cost-effective manner. While more sensitive technology has aided in identifying salivary biomarkers and detecting them in very small quantities, clinical testing applications for systemic conditions remain relatively few.

That distal systemic disease is reflected in the constituents of saliva is enormously significant and potentially highly clinically meaningful for the early detection of disease, monitoring disease progression, and predicting therapeutic outcomes. Salivary biomarkers for disease detection (both oral and systemic), particularly for molecular oncology, are emerging where blood markers are still elusive. Renowned saliva researcher David Wong, D.M.D., Ph.D., the associate dean of research at the UCLA School of Dentistry, says the systemic oncological diseases his lab has studied (including pancreatic cancer, breast cancer, lung cancer, gastric cancer, and ovarian cancer) have all yielded “highly discriminatory” salivary biomarkers. While saliva-based oncological diagnostics may be several years away, routine screening for chronic conditions may be coming to a dentist office soon.

Dentists Take Note
Saliva has attracted widespread interest as a diagnostic medium for rapid, point-of-care testing and dentists have taken active roles in working to integrate the tests into clinical practice.

The role of prevention and the improved integration of health care providers across disciplines frequently emerge during discussion of efforts to enact reform in the U.S. health care system. More patients visit a dentist annually than visit a physician, so utilizing dentists could be an important resource for an integrated health care delivery strategy. In an expanded care role, dentists could screen for underlying conditions in addition to providing oral health care. Utilization of a saliva-based diagnostic platform fits logically into this scenario.

Research suggests that the majority of dentists feel diagnostics screening is important and they are willing to conduct screening for medical conditions. Screening for nonoral conditions could likely include systemic diseases such as cardiovascular and respiratory diseases, diabetes mellitus, HIV/AIDS, and hepatitis.

Patient acceptance of “chairside medical screening” in a dental setting is a critical element for the successful implementation of this strategy. A study of patient attitudes toward chairside medical screening in dental settings was published online in the Journal of Public Health Dentistry in October 2011. The majority of respondents surveyed in both private practice settings (170) and an inner-city dental school clinic (263) were willing to have a dentist conduct screening for heart disease, high blood pressure, diabetes, HIV, and hepatitis infection (55 percent to 90 percent). Sixty percent to 94 percent of respondents were willing to provide oral fluids, finger-stick blood, blood pressure measurements, and height and weight in a dental setting, and half to two-thirds were willing to pay up to $20 for the screening. The fact that the test was not done by a physician was ranked as the least important potential barrier. While all respondents expressed a favorable attitude toward chairside screening, the mean score was significantly lower among clinic patients across most questions.

“The [American Dental Association (ADA)] is embracing it. Nearly 175,000 dentists [can be mobilized to] integrate saliva diagnostic testing in the next two to three years,” says Wong. “The ADA sees this as a scientifically driven clinical agenda. Third-party payers are in the picture and on board. The dentist of the future will integrate noninvasive testing and saliva integrates perfectly into it.”

The ADA has approved two saliva-diagnostic-related reimbursement codes, Wong says, but they are waiting for a credible test to be ready.