Noninvasive Method for Glucose Level Estimation by Saliva

The most commonly used laboratory diagnostic procedures involve the analysis of cellular and chemical constituents of blood. Other biological fluids are utilized for the diagnosis of disease. Saliva offers some distinctive advantages. Whole saliva can be collected non-invasively and by individuals with limited training. No special equipment is needed for collection of the fluid. Diagnosis of disease via the analysis of saliva is potentially valuable for children and older adults, since collection of the fluid is associated with fewer compliance problems as compared with the collection of blood. Further analysis of saliva may provide a cost-effective approach for the screening of large populations. Saliva can be considered as gland-specific saliva and whole saliva. Gland-specific saliva can be collected directly from individual salivary glands: parotid, Submandibular, sublingual, and minor salivary glands. Secretions from both the Submandibular and sublingual salivary glands enter the oral cavity through Wharton’s duct and thus the separate collection of saliva from each of these two glands is difficult [1]. The collection and evaluation of the secretions from the individual salivary glands are primarily useful for the detection of gland-specific pathology i.e. infection and obstruction. However, whole saliva is most frequently studied when salivary analysis is used for the evaluation of systemic disorders. Whole saliva (mixed saliva) is a mixture of oral fluids and includes secretions from both the major and minor salivary glands. Saliva in addition to several constituents of non-salivary origin, such as GCF, gingival crevicular fluid expectorated bronchial and nasal secretions, serum and blood derivatives from oral wounds, bacteria and bacterial products, viruses and fungi, desquamated epithelial cells, other cellular components and food debris [2-4] can be collected with or without stimulation. Saliva is collected by gustatory stimulation i.e. application of citric acid on the subject’s tongue [5]. Stimulation obviously affects the quantity of saliva; however, the concentrations of some constituents and the pH of the fluid are also affected. Unstimulated saliva is collected without exogenous gustatory, masticatory or mechanical stimulation. Unstimulated salivary flow rate is most affected by the degree of hydration but also by olfactory stimulation, exposure to light, body positioning and seasonal as well as diurnal factors. The best two ways to collect whole saliva are the draining method in which saliva is allowed to drip off the lower lip. Another one is spitting method in which the subject spits saliva into a test tube [1]. Different reagents are used to determine the content of saliva. Molisch test gives a positive result of purple colour that reveals presence of carbohydrates. Small amounts of organic nonprotein compounds, uric acid, bilirubin and creatinine can be detected in saliva. Saliva moreover contains glucose, amino acids, lipids like cholesterol and mono/diglycerides of fatty acid [6] saliva may be useful for the diagnosis of hereditary disorders, autoimmune diseases, malignant and infectious diseases, and endocrine disorders, as well as in the assessment of therapeutic levels of drugs and the monitoring of illicit drug use [7].