Saliva analysis in the clinical setting: revisiting an underused diagnostic tool

A comprehensive salivary analysis for oral cancer diagnosis

PURPOSE

This study utilized comprehensive salivary analysis to evaluate biochemical and immunological parameters in the saliva of oral squamous cell carcinoma (OSCC) patients.

METHODS

Whole saliva was collected from 25 otherwise healthy OSCC patients and compared to 25 healthy, age- and gender-matched individuals. All OSCC lesions were located at the lateral aspect of the mobile tongue. The salivary parameters analyzed included: sodium (Na), potassium (K), calcium (Ca), inorganic phosphate (P), magnesium (Mg), total protein (TP), albumin (Alb), lactate dehydrogenase (LDH), amylase (Amy), total immunoglobulin G (IgG), secretory immunoglobulin A (Sec. IgA), epidermal growth factor, insulin growth factor I (IGF-I) and metalloproteinases MMP-2 and MMP-9.

RESULTS

In cancer patients, salivary median total protein concentration was significantly higher by 26% (P = 0.01), as were concentrations of Na, Ca, P and Mg by 14% (P = 0.05), 59% (P = 0.05), 39% (P = 0.08) and 28% (P = 0.12), respectively. Amy and K concentrations were lower by 25% (P = 0.12) and 15% (P = 0.03), respectively. Alb was 108% higher (P = 0.0007), as were salivary LDH (88%, P = 0.002) and total IgG (125%, P = 0.01), while Sec. IgA was lower by 45% (P = 0.001). Concentrations of IGF, MMP-2 and MMP-9 were significantly higher by 117% (P = 0.03), 75% (P = 0.0003) and 35% (P = 0.05), respectively.

CONCLUSIONS

Comprehensive salivary analysis revealed an overall altered salivary composition in OSCC, indicating a compromised oral environment in these patients and suggesting salivary analysis as a new diagnostic tool for oral cancer. Local therapeutic agents can be easily applied to the oral mucosa, altering its "bathing medium"-the saliva.

Saliva specimen: a new laboratory tool for diagnostic and basic investigation

The assay of saliva is an increasing area of research with implications for basic and clinical purposes. Although this biological fluid is easy to manipulate and collect, careful attention must be directed to limit variation in specimen integrity. Recently, the use of saliva has provided a substantial addition to the diagnostic armamentarium as an investigative tool for disease processes and disorders. In addition to its oral indications, the analysis of saliva provides important information about the functioning of various organs within the body. In this respect, endocrine research certainly occupies a central role. The present review considers the laboratory aspects of salivary assays with respect to the different analytes including ions, drugs and various non-protein/protein compounds such as hormones and immunoglobulins. This review also examines the consequences of preanalytical variation with respect to collection strategy and subsequent storage conditions. It is likely that the use of saliva in assays will continue to expand thus providing a new instrument of investigation for physiologic as well as pathophysiologic states.

Age- and flow-dependency of salivary viscoelasticity

Measuring salivary viscoelasticity (by relaxation times) is of paramount importance, since salivary rheology behavior has been associated with the development of oral disease conditions (such as dental caries) in animal and human model studies. In addition, novel and improved methods to evaluate salivary distribution and lubrication are of clinical interest. We used a novel method for measuring the viscoelasticity of saliva secreted from the different glands, at rest or under stimulation and at different ages, all conditions where different viscoelastic properties might be clinically important. Submandibular/sublingual salivary viscoelasticity was significantly higher than that of parotid saliva, especially under stimulation. In addition, an age-related reduction in flow rate (by 62%) was demonstrated, accompanied by an increase in both relaxation time (by 54%) and protein (by 48%). Increased salivary viscoelasticity results in compromised salivary rheology and lubrication properties, which may render the oral cavities of the elderly and other xerostomic persons more vulnerable.

Implications for diagnostics in the biochemistry and physiology of saliva

Oral fluid mainly consists of a mixture of glandular salivas. In addition, it is contaminated by some crevicular fluid, containing serum constituents. The contribution of the various salivary glands shows a continuous variation, resulting in wide ranges of concentrations for all constituents of oral fluid. As a consequence, the collection of oral fluid for diagnostic purposes should be standardized. Oral fluid can be used to detect a number of diseases and recent use of illicit drugs. It can also be used to monitor therapeutic drug concentrations. The development of microchips for salivary components offers great possibilities to use oral fluid for point-of-care testing.

Oxidative stress indices in COPD--Broncho-alveolar lavage and salivary analysis

OBJECTIVE

It has been suggested that oxidative stress plays a role in the pathogenesis of chronic obstructive pulmonary disease (COPD), though this role has yet to be fully elucidated. The purpose of this study was to further evaluate this role as concomitantly expressed in the saliva and broncho-alveolar lavage (BAL/'lavage').

DESIGN

Forty consenting patients (mean age 62+/-13-year-old), with/without COPD and/or smoking habit, participated in the study. The following antioxidant profile was examined both in saliva and lavage of the patients: total antioxidant status (TAS), uric acid (UA), peroxidase and super oxide dismutase (SOD). Total protein (TP) and albumin (Alb) were also evaluated in both saliva and lavage while amylase was measured only in saliva.

RESULTS

Increase of TAS (by 100%) and of SOD activity levels (by 60%) in the lavage of COPD patients indicated oxidative stress. The salivary UA in COPD patients was 125% higher (p = 0.05) while the peroxidase was 20% higher. Another novel finding was that levels of salivary antioxidants in smoking versus non-smoking COPD patients were lower by 25-48% (for all four: TAS, UA, peroxidase and SOD) while the albumin was significantly reduced by 60% (p = 0.018).

CONCLUSION

Oxidative-stress-related changes demonstrated both in the lavage and saliva of the COPD and/or smoking patient indicate cumulative effects of both, also emphasizing the pathogenetic role of free radicals in COPD. Salivary analysis, which is less invasive and much easier to perform as compared with lavage analysis, is suggested as a new and effective diagnostic tool in COPD patients.

Characterization of the human salivary proteome by capillary isoelectric focusing/nanoreversed-phase liquid chromatography coupled with ESI-tandem MS

Saliva is a readily available body fluid with great diagnostic potential. The foundation for saliva-based diagnostics, however, is the development of a complete catalog of secreted and "leaked" proteins detectable in saliva. By employing a capillary isoelectric focusing-based multidimensional separation platform coupled with electrospray ionization tandem mass spectrometry (MS), a total of 5338 distinct peptides were sequenced, leading to the identification of 1381 distinct proteins. A search of bacterial protein sequences also identified many peptides unique to several organisms and unique to the NCBI nonredundant database. To the best of our knowledge, this proteome study represents the largest catalog of proteins measured from a single saliva sample to date. Data analysis was performed on individual MS/MS spectra using the highly specific peptide identification algorithm, OMSSA. Searches were conducted against a decoyed SwissProt human database to control the false-positive rate at 1%. Furthermore, the well-curated SwissProt sequences represent perhaps the least redundant human protein sequence database (12,484 records versus the 50,009 records found in the International Protein Index human database), therefore minimizing multiple protein inferences from single peptides. This combined bioanalytical and bioinformatic approach has established a solid foundation for building up the human salivary proteome for the realization of the diagnostic potential of saliva.

Free radicals related effects and antioxidants in saliva and serum of adolescents with Type 1 diabetes mellitus

OBJECTIVE

The purpose of the current study was to analyze both serum and salivary composition and oxidative stress markers in Type 1 diabetes mellitus (DM) patients.

DESIGN

Twenty consenting patients with DM but otherwise healthy patients aged 13-19 years and 12 healthy controls, matching in age and gender (Group 1), participated in the study. The patients were divided according to those who had controlled diabetes mellitus (Group 2) or uncontrolled diabetes mellitus (Group 3). All were analyzed for saliva composition and antioxidants. Saliva was also analyzed for its levels of superoxide dismutase (SOD) and amylase activity, total IgA and total IgG concentrations and potassium, phosphorus, magnesium and calcium electrolyte concentrations.

RESULTS

A significant correlation was found between the severity of the DM/HbA1c values and the increase in both salivary and/or serum antioxidants (peroxidase, SOD and TAS), and the various TCL parameters (H1, H3, pre-incubation and oxygenation-potential).

CONCLUSIONS

The two most important findings of the current study relate to the role of oxidative stress in the pathogenesis of Type 1 diabetes mellitus and to the involvement of salivary glands in the disease. The profound effects of DM on salivary antioxidant parameters may be also of great importance in respect to the diagnosis and evaluation of the disease. The correlation between altered salivary parameters and the severity of the disease may indicate that evaluation of the salivary status of DM patients as part of the assessment of their disease activity and severity is warranted.

Salivary levels of CGRP and VIP in rhinosinusitis and migraine patients

BACKGROUND

Secretion of calcitonin gene-related peptide (CGRP) from trigeminal nerves and vasoactive intestinal peptide (VIP) from parasympathetic nerves is involved in the pathophysiology of migraine and rhinosinusitis. Analysis of these neuropeptides in human saliva samples can be used as markers of trigeminal and parasympathetic nerve activity in patients between and during attacks as well as in response to specific treatments.

OBJECTIVE

To compare the amount of trigeminal sensory and parasympathetic nerve activation by measuring CGRP and VIP levels in the saliva of subjects experiencing noninfectious allergic rhinosinusitis, migraine with sinus symptoms, and no symptoms.

METHODS

Subjects were enrolled in three groups. Group A: subjects without a history of migraine, "sinus" headache, or allergic rhinosinusitis within the previous 6 months. Group B: subjects with chronic recurrent noninfectious rhinosinusitis and no history of migraine or "sinus" headache. Group C: subjects with self-described "sinus" headaches whose symptoms met International Headache Society diagnostic criteria (1.1 or 1.2) for migraine. The total amount of CGRP and VIP present in saliva collected under normal, pathological, and therapeutic conditions was determined by radioimmunoassay. Neuropeptide levels were normalized to total volume and amount of protein, and levels were correlated to onset and change in clinical symptoms.

RESULTS

Total volume, total protein, and CGRP and VIP levels did not significantly change in saliva collected on consecutive days in the clinic and at the subject's home, respectively. No appreciable change in baseline salivary levels of CGRP and VIP was detected in control subjects. However, baseline salivary levels of CGRP and VIP were significantly elevated between attacks in allergic rhinosinusitis and migraine subjects compared to control values. For rhinosinusitis subjects, the amount of CGRP and VIP during attacks returned to baseline values following treatment with pseudoephedrine and relief of symptoms. Similarly, CGRP and VIP levels during a migraine headache were significantly reduced within 2 hours after sumatriptan treatment and reported symptom relief.

CONCLUSION

Correlation of CGRP and VIP saliva levels observed in our study supports physiologically coordinated regulation of trigeminal and parasympathetic nerve activation in allergic rhinosinusitis and migraine patients between and during attacks as well as following treatment. Furthermore, our findings demonstrate that analysis of human saliva neuropeptides may provide a semiquantitative index of pathological and therapeutic states and, therefore, function as a clinical model for studying neuronal mechanisms involved in migraine and rhinosinusitis.

Effect of saliva collection method on the concentration of protein components in saliva

In order to clarify how we collect saliva for analyzing salivary protein in aged subjects who can not eat well, we compared the effects of suction, spitting and the swab saliva collection method on the yield of protein components in saliva samples from normal volunteers. The saliva collected by suction, spitting and the swab method were designated as, Saliva I, II and III, respectively. The saliva volume collected by Saliva I was about 2-fold greater than that by of Saliva II and III. This is mainly due to the fact that saliva secretion was stimulated by the suction itself. The content of total protein, S-IgA, trypsin-like activity and human airway trypsin-like protease (HAT) were almost the same in Saliva I and II, and significantly lower in Saliva III than in Saliva I and II. Kallikrein activity was almost the same in Saliva I, II and III. The concentration of each total protein, S-IgA, kallikrein activity, trypsin activity and HAT in Saliva I were significantly positively correlated with that in Saliva II. These results indicate that we can obtain information of change of salivary protein by analyzing saliva collected by suction method, although this method caused the stimulation of saliva to some extent.

Age-related changes in unstimulated salivary function and composition and its relations to medications and oral sensorial complaints

BACKGROUND AND AIMS

The purpose of the current study was to examine the salivary flow rate and composition in relation to drug consumption and idiopathic oral sensorial complaints (OSC). OSC cover xerostomia, disturbed sense of taste, or burning mouth sensitivity with no established classical etiology (e.g., Sjogren's syndrome, or a response to radiotherapy).

METHODS

A thorough sialometrical and sialochemical analysis was performed for all subjects who were healthy non-hospitalized individuals ranging in age from 18-89 years. Saliva samples were all collected in unstimulated conditions.

RESULTS

The three most significant observations were: a) Elderly people have significantly reduced and altered salivary secretion. Whereas specific concentrations increased, the total values of most salivary components were found to be decreased in the elderly. b) Fifty percent of the elderly make OSC. c) OSC were made mainly by elderly individuals who use drugs.

CONCLUSIONS

Reduction in salivary function and altered composition are age-related. However, when drugs are not involved, a compensatory capacity which avoids OSC apparently exists. In contrast, the effect of drugs on OSC is extensive. The finding that the total amount of salivary components and not only salivary flow rates are reduced in the elderly is of great clinical importance, since such a reduction is expected to be reflected in compromising various salivary functions.

Development of an oral biosensor for salivary amylase using a monodispersed silver for signal amplification

An amperometric biosensor for monitoring the level of protein amylase in human saliva is described. A novel design and the preparation of amylase antibodies and antigens, essential for the development of the biosensor, are reported. The biosensor sensing elements comprise a layer of salivary antibody (or antigen) self-assembled onto Au-electrode via covalent attachment. Molecular recognition between the immobilized antibody and the salivary amylase proteins was monitored via an electroactive indicator (e.g., K(3)Fe(CN)(6)) or a monodispersed silver layer present in solution or electrochemically deposited onto the solid electrode. This electroactive indicator was oxidized or reduced and the resulting current change provided the analytical information about the concentration of the salivary proteins. The limit of detection of 1.57 pg/ml was obtained, in comparison to detection limits of 4.95 pg/ml obtained using potassium ferrocyanide as the redox probe and 10 ng/ml obtained using enzyme-linked immunosorbent assay. Cross-reactivity was tested against cystatin antibodies and was found to be less than 2.26%.

Toward defining the human parotid gland salivary proteome and peptidome: identification and characterization using 2D SDS-PAGE, ultrafiltration, HPLC, and mass spectrometry

Saliva plays many biological roles, from lubrication and digestion to regulating bacterial and leukocyte adhesion. To understand the functions of individual components and families of molecules, it is important to identify as many salivary proteins as possible. Toward this goal, we used a proteomic approach as the first step in a global analysis of this important body fluid. We collected parotid saliva as the ductal secretion from three human donors and separated the protein components by two-dimensional SDS-polyacrylamide gel electrophoresis (2D SDS-PAGE). Proteins in gel spots were identified by peptide mass fingerprinting, and the results were confirmed by tandem mass spectrometry of selected peptides. Complementing this approach we used ultrafiltration to prepare a low-molecular-weight fraction of parotid saliva, which was analyzed directly or after reversed phase high-performance liquid chromatography separation by using mass spectrometric approaches. MS analyses of 2D SDS-PAGE spots revealed known components of saliva, including cystatins, histatins, lysozyme, and isoforms and/or fragments of alpha-amylase, albumin, and proline-rich proteins. We also discovered novel proteins, such as several isoforms of Zn-alpha-2-glycoprotein and secretory actin-binding protein. MS analyses of the ultrafiltrate showed that the low-molecular-weight fraction of parotid saliva was peptide-rich, with novel fragments of proline-rich proteins and histatins in abundance. Experiments using Candida albicans as the test organism showed that at least one of the novel peptides had antifungal activity. Our results show that saliva is a rich source of proteins and peptides that are potential diagnostic and therapeutic targets.

Relationships between age, drugs, oral sensorial complaints and salivary profile

The aim of this study was to investigate the relationships between oral sensorial complaints (OSCs) and salivary flow rate, composition and drug consumption of subjects aged 18-90 years. The results were correlated with both drug consumption and OSCs. Only individuals who were free of conditions that are already known to cause OSCs were included in the study. The three most significant observations were as follows: (1) elderly people have significantly reduced and altered salivary secretion compared with younger people. While specific concentrations increased, the total values of most salivary components decreased in the elderly; (2) 50% of the elderly population have OSCs regarding taste, burning mouth syndrome or xerostomia; and (3) OSCs were more prevalent in elderly people who use drugs than in those who do not. In conclusion, a reduction in salivary function and altered composition are age related. A compensatory capacity that prevents OSCs appears to exist in elderly patients who do not use drugs, but drugs were found to have an extensive effect on OSCs. The finding that the total amounts of salivary components and not only the salivary flow rate were reduced in elderly people is of great clinical relevance, since such a reduction is expected to be reflected in compromising various salivary functions.

Salivary levels of tumor necrosis factor-alpha in oral lichen planus

OBJECTIVE

Oral lichen planus (OLP) is chronic inflammatory disease of the oral mucosa, presenting in various clinical forms. The etiology of OLP is still unknown but mounting evidence points to the immunologic basis of this disorder.

AIM

Our study was undertaken to quantify the salivary levels of pro-inflammatory tumor necrosis factor-alpha (TNF-alpha) in the reticular and the erosive/atrophic forms of OLP, compared with age-matched healthy control volunteers.

SUBJECTS AND METHODS

Whole saliva from 40 patients with active lesions of OLP, as well as from 20 healthy persons, was investigated for the presence of TNF-alpha by enzyme immunoassay.

RESULTS

Salivary TNF-alpha levels were significantly increased in patients with OLP in comparison with healthy subjects. The presence of TNF-alpha showed positive correlation to clinical forms of OLP, being significantly higher in the erosive/atrophic type than in the reticular type of disease.

CONCLUSION

Saliva provides an ideal medium for the detection of pro-inflammatory markers of the oral cavity. In patients with OLP, TNF-alpha levels in saliva are elevated, correlating with the severity of illness. Salivary TNF-alpha analysis may be a useful diagnostic tool and a potential prognostic marker in OLP.

Biochemical, immunological and enzymatic components of saliva in prolonged naso-gastric-fed elderly patients

BACKGROUND AND AIMS

We have previously shown that naso-gastric tube (NGT)-fed patients harbor pathogenic flora in their oropharynx. The purpose of this study was to examine comparatively the biochemical, immunological and enzymatic components of the saliva of these patients with that of orally-fed counterparts.

METHODS

The study group consisted of 19 elderly NGT-fed patients and 18 comparable patients on oral feeding. Unstimulated whole saliva was collected and analyzed according to accepted methods for sodium, potassium, chloride, uric acid, total protein, albumin, amylase, lysozyme, and immunoglobulins, IgM, IgG, IgA, as well as secretory IgA.

RESULTS

None of the above tested salivary components significantly differed between the two groups. Only uric acid levels were significantly lower (50%, p < 0.05) in NGT-fed patients.

CONCLUSIONS

Uric acid is the main antioxidant component of saliva and, as such, it may be related to pathogenic bacterial colonization of the oropharynx in NGT-fed patients, with the risk of aspiration pneumonia.

Saliva--a pivotal player in the pathogenesis of oropharyngeal cancer

Oropharyngeal (OP) cancer, which is usually squamous cell carcinoma, is the most common head and neck malignancy and accounts for 2–4% of all new cancers. It is primarily induced by exposure to tobacco. The paradigm of cigarette smoke (CS)-induced OP cancer's pathogenesis is based on the assumption that a constant direct attack of various CS carcinogens causes widespread accumulating cellular and DNA aberrations in the OP mucosal cells, in turn eventually resulting in malignant transformation. However, there is never a direct contact between CS and the OP mucosa. Saliva, bathing the mucosa from the oral cavity to the larynx, always intervenes, and CS must first interact with saliva before it reaches the mucosa. The current study investigated the role of saliva in the pathogenesis of OP cancer. A synergistic effect of CS and saliva on oral cancer cells was demonstrated. This synergism is based on the reaction between redox active metals in saliva and low reactive free radicals in CS, which results in the production of highly active hydroxyl free radicals. Thus, when exposed to CS, salivary behavior is reversed and the saliva loses its antioxidant capacity and becomes a potent prooxidant milieu. The devastating role of CS-borne aldehydes was demonstrated as well. Based on these results and on our recent reports demonstrating that CS destroys various salivary components, including protective ones such as peroxidase, the most important salivary antioxidant enzyme, a comprehensive view of the pivotal role of saliva in the pathogenesis of CS-induced OP cancer is suggested.

Sialochemical and gustatory analysis in patients with oral sensory complaints

Our objective was to perform concomitant taste and salivary analyses in subjects with oral sensory complaints (OSC), including burning mouth syndrome (BMS), idiopathic taste aberrations, and xerostomia without established etiology, to attempt to find a possible explanation for the mechanism underlying those complaints. BMS is a disorder characterized by a painful burning or scalding sensation in clinically normal and healthy oral mucosa. Taste and salivary analyses were performed on 163 subjects with OSC who complained of BMS, taste aberration, or xerostomia, alone or in combination. These subjects were compared with 84 healthy, age- and sex-matched control subjects. The salivary and taste analyses were found to be helpful in distinguishing control subjects from complaining subjects. The most striking result found was the great similarity of both salivary and taste analyses in the BMS, taste aberration, and xerostomia groups, which were significantly different from the results obtained in the control group. An oral neuropathy or neurologic transduction interruption induced by salivary compositional alterations is suggested as the possible etiology for the complaints. This report might add an important objective diagnostic tool to the clinician treating such patients.

PERSPECTIVE

The merit of the current study stems from the fact that it suggests for the first time a salivary-related local neuropathic mechanism for oral sensorial complaints. This may be of paramount importance, both with respect to the biological background of these complaints and to the possible therapeutic modalities that might be offered to suffering patients.

Oral fluid as a diagnostic tool

Technological advances over the past decades have enabled oral fluid to expand its usefulness in the diagnosis of disease, prediction of disease progression, monitoring of therapeutic drug levels and detection of illicit drugs. The easy non-invasive nature of collection and the relationship between oral fluid and plasma levels make oral fluid a valuable clinical tool. This review describes advances over the past 5 years in the area of oral fluid as a diagnostic tool, its use in therapeutic and illicit drug monitoring, including proposed guidelines for cut-off values, and methods of collection.