Saliva performs a multiplicity of roles within the oral cavity, and like many things in life, its importance is usually not appreciated until it is absent. The pursuit of timely, cost-effective, accurate, and non-invasive diagnostic methodologies is an endeavour of urgency among clinicians and scientists alike and hence giving birth to saliva as a diagnostic tool. The accessibility of the mouth renders it a portal through which one can potentially monitor systemic and oral health. For the past two decades, salivary diagnostic approaches have been developed to monitor oral diseases such as periodontal diseases and to assess caries risk.
Why Saliva ?
Saliva has been studied extensively as a potential diagnostic tool over the last decade due to its ease and non-invasive accessibility along with its abundance of biomarkers, such as genetic material and proteins. Like serum, saliva also contains hormones, antibodies, growth factors, enzymes, microbes and their products. The composition of saliva varies from site to site within the mouth of the one individual, and changes according to the time of day and proximity to meals. Its properties are affected by the level of hydration and general health of the individual. Water makes up approximately 99% of the volume of saliva, and serves as the solvent for the other components that make up saliva.
Advantages of Saliva as diagnostic tool
- Non-invasive, easy to use, inexpensive.
- Safer to administer than serum sampling (no needles).
- Real-time diagnostic values.
- Multiple samples can be obtained easily.
- Collection and screening can be done at home.
- Minimal risks of cross-contamination.
- More economical sampling, shipping and storage compared to serum.
There have been concerns about the use of saliva for diagnostic purposes due to its low concentration of analytes in comparison to blood. However, with the advent of highly sensitive molecular methods and nanotechnology, this is no longer a limitation.
Applications of saliva as diagnostic tool
- Sjogren’s syndrome (SS) is a chronic autoimmune disease characterized by salivary and lacrimal dysfunction, multiple organ abnormalities and serological changes. Current tests for SS include sialometry or salivary flow rate determination, salivary scintigraphy, sialography, serological tests or minor salivary gland biopsies.
- Cystic fibrosis (CF), one of the most frequent hereditary disease in Caucasians, typically leads to early death from respiratory complications. Saliva of CF patients has increased levels of calcium and phosphate, which may explain higher incidence of calculus observed in such individuals. These patients also harbour higher salivary levels of chloride, potassium and sodium ions with a lower salivary volume and pH compared to healthy individuals.
- To detect HIV, swab is left in place for 2–5 min between the lower gingival and buccal mucosa to collect antibodies in the saliva.
- Several research groups have found that salivary levels of specific proteins are increased in whole saliva of patients with Oral Squamous Cell Carcinoma(OSCC).
- Saliva is also used in monitoring drug in the body.
Considering the accuracy, efficacy, ease of use and cost effectiveness, salivary diagnostic tests have demonstrated their applications in clinical and basic sciences. Moreover, salivary-based diagnostic techniques can potentially allow screening of an entire population for a specific disease in a timely fashion.
Author: Dr. Siri P. B.