Disease, Detection and DNA: What your saliva says about you


Research has shown that human saliva holds a treasure trove of data related to human biology and genetics. This aids in the diagnosis and monitoring of disease and adds to a health professionals’ arsenal in determining the most appropriate ways to detect and treat diseases.

Research conducted by the Johns Hopkins University Centre for Interdisciplinary Bioscience Research1 explores the composition and utility of human saliva as a means for medical diagnostics. Saliva collection is both less invasive and less expensive than traditional blood or urine sampling, serving as a gateway for revolutionary technology in the healthcare industry, particularly in replacing existing medical testing methods that may be less effective in detecting diseases.

A closer look into saliva

Beyond its more obvious functions in taste and digestion, saliva contains a variety of biomarkers, that are effective in diagnosing and monitoring a range of disorders from cancer to infectious disease.

One such biomarker is an antibody; one of our bodies defence mechanisms against infectious diseases. This immune response is part of the adaptive immune system, protecting us from becoming sick when our body’s encounter the same pathogen again. Antibodies are therefore measurable indicators of exposure to different diseases.

Saliva contains a ‘biological motherload’ of genetic material from which an individual’s unique blueprint or ‘spit print’ can be determined. Human saliva yields DNA of a similar quality to blood, meaning that saliva can be used for similar genetic applications when compared to blood-based testing 1. Most of the DNA in saliva comes from white blood cells, which are a great source of high-quality genomic information2. Genetic information is incredibly valuable in the diagnostic setting as it can be utilised to measure the risk and likelihood of a person developing a particular disease. Genetic information also provides insight into what kinds of treatment will work best for an individual, leading to more personalised medicine and better health outcomes for the patient.

Conveniently, a human adult will produce around 1.5L of saliva per day. And so, a once underappreciated digestive fluid has in fact turned out to be capable of providing a comprehensive view of an individual’s health status.

How your saliva could save your life

Saliva-based testing can be used to inform medical decision making when treating and managing diseases. Research centres around the globe are incorporating salivary biomarkers into their diagnostic activities, with one of the biggest accomplishments to date being the detection of HIV in saliva3. Scientists have since discovered that a number of other infectious diseases such as; Ebola Virus, Dengue Fever, measles and even the notorious SARS-CoV-2 can be detected in human saliva4.

Researchers at the Johns Hopkins University Centre for Interdisciplinary Bioscience Research are also suggesting that saliva can be used to monitor stress levels5, by the measurement of salivary alpha-amylase (sAA). sAA is present when the body’s ‘fight or flight’ response is activated. Saliva testing can also be used to indicate human heart health through the detection of elevated c-reactive proteins, which are also found in the blood. Beyond human health, there are many other real-world usage cases for oral-fluid testing yet to be explored, such as by law enforcement agencies to detect alcohol intoxication and to test for illicit substance abuse.

Saliva is more attractive than blood in these examples as it allows for multiple samples to be taken each day without the need for trained medical practitioners. The sampling procedure is also far more economical as saliva is easily collected, shipped and stored, resulting in decreased costs for both healthcare practitioners and patients alike6.

A new future for pathology

Not only are saliva tests less invasive but they can be self-collected, are pain-free and allow for repeated daily testing, therefore bypassing many of the limitations associated with blood or urine-based tests.

On an epidemiological level, these tests can significantly improve community-wide disease surveillance, as well as increase disease sampling from a global population pool. It is because of these benefits, and the fact that new, and some of the same proteins that exist in both human blood and saliva, that leading researchers are proposing that saliva testing could potentially replace blood for some biomarkers7.

However, it is not as easy as it seems. Despite these favourable attributes, the use of saliva diagnostics is not yet a mainstream idea. This is mainly because traditional blood point of care diagnostics are not sensitive or accurate enough to perform quantitative measurements in human saliva. Given that the vast majority of disease-specific biomarkers are still largely unknown, it is clear we have an opportunity to provide information on saliva biomarkers that are found in concordance with blood but also potentially new information that exists only in saliva.

For a saliva-based test to be successful, it should provide non-invasive, accurate, disease-specific and rapid measurements, as well as be inexpensive and portable.

The future of saliva-based testing

The iQ Group Global’s Biosensor Diagnostic and Monitoring Platform utilises human saliva, collected on a small, organic diagnostic ‘strip’ to test for a range of oral-fluid biomarkers. The core Organic Thin Film Transistor (OTFT) technology enables the testing ability of more than 130 biomarkers, ranging from glucose for diabetes management, to different antibodies against SARS-CoV-2, to hormones and nucleic acids. Depending on the analyte of interest, the detection element of the Biosensor can be altered to rapidly produce new saliva-based diagnostic tests.

With the Biosensor Platform, The iQ Group Global is powering the future of medical diagnostics and enabling patients to take control of their health.


References

1. Granger DA, Johnson SB, Szanton SL, Out D, Schumann LL. Incorporating salivary biomarkers into nursing research: an overview and review of best practices. Biol Res Nurs. 2012;14(4):347-356. doi:10.1177/1099800412443892   

2. GARBIERI T, BROZOSKI D, DIONÍSIO T, SANTOS C, NEVES L. Human DNA extraction from whole saliva that was fresh or stored for 3, 6 or 12 months using five different protocols. Journal of Applied Oral Science. 2017;25(2):147-158. doi:10.1590/1678-77572016-0046

3. Freel S, Williams J, Nelson J et al. Characterization of Human Immunodeficiency Virus Type 1 in Saliva and Blood Plasma by V3-Specific Heteroduplex Tracking Assay and Genotype Analyses. J Virol. 2001;75(10):4936-4940. doi:10.1128/jvi.75.10.4936-4940.2001

4. Corstjens PL, Abrams WR, Malamud D. Detecting viruses by using salivary diagnostics. J Am Dent Assoc. 2012;143(10 Suppl):12S-8S. doi:10.14219/jada.archive.2012.0338

5. Liu Y, Granger D, Kim K, Klein L, Almeida D, Zarit S. Diurnal salivary alpha-amylase dynamics among dementia family caregivers. Health Psychology. 2017;36(2):160-168. doi:10.1037/hea0000430

6. Yoshizawa JM, Schafer CA, Schafer JJ, Farrell JJ, Paster BJ, Wong DTW, Salivary Biomarkers: Toward Future Clinical and Diagnostic Utilities. Clinical Microbiology Reviews. 2013;26(4);doi:10.1128/CMR.00021-13

7. Hettegger P, Huber J, Paßecker K et al. High similarity of IgG antibody profiles in blood and saliva opens opportunities for saliva based serology. PLoS ONE. 2019;14(6):e0218456. doi:10.1371/journal.pone.0218456

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