Saliva testing is a diagnostic technique involving laboratory analysis of saliva to identify endocrine markers, immunology, inflammation, infections, and other types of conditions. Saliva is a biologic fluid that is useful for testing steroid hormones such as cortisol, genetic material such as RNA, proteins such as enzymes and antibodies, and various other substances, including natural metabolites, including salivary nitrite, biomarkers for nitric oxide status (see below). for Cardiovascular Disease, Nitric Oxide: salivary biomarker for cardio protection). Saliva tests are used to filter or diagnose various conditions and conditions of the disease, including Cushing's disease, anovulation, HIV, cancer, parasites, hypogonadism, and allergies. Saliva testing has even been used by the US government to assess circadian rhythm shifts in astronauts before flights and to evaluate the hormonal profile of soldiers undergoing military survival training.
Supporters of saliva testing mention the ease of collection, safety, noninvasive, affordability, accuracy, and capacity to avoid venipuncture as a major advantage when compared with blood tests and other types of diagnostic tests. In addition, since some samples can be easily obtained, saliva testing is useful for performing chronobiological assessments that include hours, days, or weeks. Gathering all the saliva with passive saliva has a lot of advantages. The collection of passive saliva facilitates the collection of large sample sizes. Consequently, it allows samples to be tested for more than one biomarker. It also gives researchers the ability to freeze the remaining specimens to be used at a later time. In addition, reducing the possibility of contamination by removing additional collection devices and the need to induce salivary flow.
The clinical use of saliva tests occurred at least in early 1836 in patients with bronchitis. Saliva acidity testing occurred at least in early 1808. Saliva testing of saliva was performed at least in early 1685.
More recent studies have focused on the detection of steroid hormones and antibodies in the saliva. Recent applications emphasize the development of increasingly sophisticated techniques for detecting additional proteins, genetic material, and markers of nutritional status. According to Wong, scientists now see saliva as a "valuable biofluid... with the potential to extract more data than is currently possible with other diagnostic methods."
Video Saliva testing
Technology
Most saliva testing is performed using enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), high-resolution mass spectrometry (HRMS), or a number of new technologies such as fiber-optic-based detection. All of these methods allow detection of specific molecules such as cortisol, C-reactive protein (CRP), or secretory IgA. This type of testing usually involves the collection of a small amount of saliva into a sterile tube followed by processing in a remote laboratory. Some testing methods involve the collection of saliva using absorbent pads, applying chemical solutions, and monitoring color changes to show positive or negative results. This method is usually used as a point-of-care (POC) technique for HIV screening. However, using absorbent pads and chemical solutions can easily alter the results of immunoassays. Research by Dr. Douglas A. Granger and colleagues showed that results for testosterone, DHEA, progesterone, and estradiol biomarkers increased when cotton-based collection materials were used as opposed to samples collected by other methods (ie passive saliva). Researchers are currently examining the role of widespread testing of saliva as part of routine dental or medical checkups where saliva collection is easy to do.
Maps Saliva testing
Physiologically
Humans have three major salivary glands: parotid, submandibular, and sublingual. This gland, together with the addition of a small salivary gland, secretes a rich mixture of biological chemicals, electrolytes, proteins, genetic material, polysaccharides, and other molecules. Most of these substances enter the salivary saline asinus and the channel system of the surrounding capillaries through the intervening tissue fluid, although some substances are produced within the gland itself. The level of each salivary component varies depending on the health status of the individual and the presence of the disease (oral or systemic). By measuring these components in the saliva, it is possible to screen out various infections, allergies, hormonal disorders, and neoplasms.
Clinical use
The following conditions include those that can be detected through saliva tests (incomplete list): adrenal conditions (such as disease/Cushing's syndrome and Addison's disease), changes in female hormonal status (such as polycystic ovary syndrome [PCOS], menopause, anovulation, and hormonal changes in cycling women), changes in male hormone status (such as hypogonadism/andropause and hyperestrogenic), metabolic disorders (such as insulin resistance, diabetes, and metabolic syndrome), benign and metastatic neoplasms (such as breast cancer, pancreatic cancer and oral cancer) infections (such as HIV, viral hepatitis, amoebiasis, and helicobacter pylori infection), and allergic conditions (such as food allergies).
Use in behavioral research
Saliva tests also have special uses in clinical and experimental psychological settings. Because of its ability to provide insight into human behavior, emotions, and developments, it has been used to investigate psychological phenomena such as anxiety, depression, PTSD, and other behavioral disorders. The main purpose is to test the levels of cortisol and alpha amylase, which indicate the level of stress. Saliva cortisol is a good stress index, with elevated levels of cortisol positively associated with increased stress levels. Cortisol levels increase slowly over time and take time to return to baseline levels, suggesting that cortisol is more associated with chronic stress levels. Alpha amylase, on the other hand, spikes quickly when confronted with a stressor and returns to the baseline as soon as stress has passed, making the salivary amylase measurement a powerful tool for psychological research studying acute stress responses. Samples are usually collected from participants by having them salivate through a straw into the collection tube when subjected to a stimulus, with samples taken every few minutes to record gradual changes in stress hormone levels. Since the collection of saliva samples is non-invasive, it has the advantage of not introducing further stress to participants who can change the outcome.
In a more specific study looking at the relationship between cortisol levels and psychological phenomena, it has been found that chronic stressors such as life-threatening situations (eg illness), depression, and social or economic difficulties are correlated with significantly higher cortisol levels. In situations where subjects experience induced anxiety, high cortisol levels are consistent with more physiological symptoms of anxiety, such as increased heart rate, sweating, and skin conductance. In addition, a negative correlation was found between baseline rates of cortisol and aggression. Saliva cortisol levels can provide insight into a number of other psychological processes.
The level of alpha amylase in saliva provides a non-invasive way to check for medullary sympathoadrenal activity (SAM), which can be measured by electrophysiological equipment or blood plasma readings. Salivary alpha salivary alpha levels have been found to correlate with high levels of activity of the autonomic nervous system, reacting in a manner similar to norepinephrine hormone. Subsequent findings revealed the relationship between the elderly and the competition. The results show that alpha amylase levels change when reacting to competition, but not when anticipating. Furthermore, by testing the level of alpha amylase, scientists see differences in reactivity behavior among individuals with prior experience in similar situations.
While saliva testing has promise to be a valuable tool and more widely used in future psychological research, there are also some disadvantages to methods to keep in mind, including the cost of collection and sample processing and the reliability of the size itself. There is a large amount of in-person variability and among those in cortisol levels to be taken into account when drawing conclusions from the study.
Much research has been done to further examine the variables that contribute to these in-person and inter-person variations. Analysis of variables affecting cortisol levels has resulted in an extensive list of confounding variables.
Diurnal variation is a major factor for in-person variance because baseline cortisol levels have been known to differ by day time. For a normal developing individual who follows a typical day-night schedule, the peak of cortisol production during the last few hours of sleep. This peak is thought to help prepare the body to act and stimulate appetite when waking up. Diurnal variations are also influenced by psychological conditions. For example, morning cortisol levels have been found to increase in shy children and late-night rates are elevated in depressed adolescents, especially between two and four o'clock in the afternoon. It may be important to understand the emotions and symptoms of depression.
Other variables affecting variations in and between people are listed below. This list is not intended to be comprehensive and the impact of many of these variables can be useful from further research and discussion.
- Age is one of the main factors for the variance between people. Several studies have shown that children and adolescents exhibit greater cortisol activity that is potentially associated with development.
- Genders have been found to affect the baseline level of cortisol, which contributes to the variance between people. In general, stressful situations, cortisol levels in men have increased to nearly twice the number when compared with women. In a stressful social situation (ie the challenge of social rejection), however, women but not men tend to show higher levels of cortisol.
- The menstrual cycle has been found to affect the level of cortisol in the body, affecting both within and among those variance. Women in the luteal phase reported to have the same cortisol levels as men, indicating no difference in sex in the cortical base level when women are not ovulating. Women in the follicular phase and women using oral contraceptives reported significantly lower cortisol levels compared with men and women in the luteal phase.
- Pregnancy has been found to increase levels of cortisol in the body. In particular, breastfeeding has been found to lower cortisol levels in the short term even if a mother is exposed to psychosocial stress.
- Nicotine is known to increase cortisol levels in the body because it stimulates the HPA axis. After at least two cigarettes, smokers showed a significant increase in salivary cortisol levels. In addition, smokers who are accustomed to show a blunted cortisol saliva response to the cause of psychological stress.
- Food has been known to affect cortisol levels. The presence of protein has been found to increase cortisol. This variable is often influenced by diurnal variation, with cortisol being particularly higher at lunch rather than at dinner, and sex, with women having higher cortisol levels after meals than men.
- While some studies examining the effects of alcohol consumption and caffeine intake at the cortisol level have found a positive correlation, the results are diverse and will benefit from further examination.
- Intense or prolonged exercise can lead to increased cortisol levels. Short-term exercise and low levels only slightly increase cortisol levels.
- Repeated exposure to early stress stimuli has been found to result in decreased levels of cortisol in the body.
- Birth weight has been shown to be inversely proportional to the cortisol base rate; low birth weight correlates with high cortisol levels.
- Position in the social hierarchy has been known to affect cortisol levels. One study specifically looked at a sample of 63 army recruits and found that socially dominant subjects showed a high increase in salivary cortisol compared with only a slight increase in subordinate men after exposure to stress and physical exercise.
- Some drugs (ie glucocorticoids, psychoactive drugs, antidepressants) have been found to affect the level of cortisol in the body but the results of studies examining this effect have been mixed. The impact of drugs on the cortical level can be useful from further research.
Recent evidence and research
Deviation of cortisol and melatonin
In 2008, the Endocrine Society published a diagnostic guide for Cushing's syndrome, where they recommended midnight saliva cortisol testing on two consecutive days as a possible early screening tool. A 2009 review concluded that late-night salivary cortisol tests are a suitable alternative for serum cortisol testing to diagnose Cushing's syndrome, reporting that both sensitivity and specificity exceeded ninety percent. In 2010 Sakihara, et al ., Evaluated the usefulness and accuracy of salivary, plasma, and urinary cortisol levels as well as determining salivary cortisol as the "preferred method" for screening for Cushing's syndrome. In 2008, Restituto, et al. ., Found salivary cortisol in the morning for "as good as serum" as the Addison disease screening technique. In 2010 Bagcim et al ., Determined that melatonin saliva levels "reflect them in serum at all times throughout the day" and are a reliable alternative to serum melatonin to study pineal physiology in newborns. A 2008 review article describes melatonin saliva testing as "a practical and reliable method for field, clinical, and research trials".
Deviation of reproductive hormone
A 2009 study examined the use of saliva tests to measure estradiol, progesterone, dehydroepiandrosterone (DHEA), and testosterone levels in 2,722 individuals (men and women). The researchers affirmed the "good validity of the measurement of sex hormones [saliva]" and concluded that salivary testing is a good method for testing older adults because of the ease in home collection.
Female
In 2010 a study identified luteinizing hormone (LH) as an accurate salivary biomarker in the ovaries of women. The researchers measured various hormones in saliva during the menstrual cycle and found that salivary luteinizing hormones increased steadily during the ovulation period and, for that reason, "salivary LH levels are a reliable way of determining ovulation." A 1983 study of various salivary steroid tests showed that daily salivary progesterone measurements "provide valuable means for assessing ovarian function". A 2001 study involves collecting saliva daily from healthy subjects and planning this during the entire menstrual cycle. The researchers determined that the salivary estradiol and progesterone curves corresponded to the daily profile normally observed in the blood, despite the lower amplitude. In 1999 the researchers determined that ELISA-based saliva testing "could serve as a reliable method for the determination of estriol." A 2007 article reported that free testosterone measurements, including through saliva tests, represent "the most sensitive biochemical markers that support the diagnosis of PCOS." In 1990, Vuorento et al., Found that a luteal phase defect, in which progesterone levels declined prematurely in the menstrual cycle, was identified with high frequency using salivary progesterone testing among women with unexplained fertility.
Men
In 2009 Shibayama et al., Examined the accuracy of salivary androgen measurements to diagnose slow-onset hypogonadism (age-related decreases in androgens, often called "andropause"). Researchers determined that the accuracy of salivary testosterone and DHEA measurements exceeded 98.5% and that this method "has a satisfactory application" in the diagnosis of late-onset hypogonadism. A 2007 study reported 100% sensitivity and specificity for saliva testosterone in excluding hypogonadism and concluded that saliva testosterone is a useful biomarker in the diagnosis of male androgen deficiency. The use of saliva testosterone for screening hypogonadism has been validated by other studies, including one involving 1,454 individuals. The researchers concluded that saliva testosterone is "an acceptable test for screening for hypogonadism."
Neoplastic conditions
Pancreatic cancer
A 2010 study by Zhang et al., Showed that the researchers were able to detect pancreatic cancer with high sensitivity and specificity (90.0% and 95.0%, respectively) by saliva screening for four specific mRNA biomarkers. In a 2011 review article examining pancreatic cancer biomarkers, Hamade and Shimosegawa concluded that the clinical application of saliva biomarker testing "is useful for screening and early detection of pancreatic cancer."
Breast cancer
In 2008 Emekli-Alturfan, et al. Comparing saliva of breast cancer patients with those of healthy and observed individuals, in particular, that breast cancer patient samples contain dysplastic cells and reduced fat peroxide. A 2000 study compared salivary levels of breast cancer markers (HER2/neu) in healthy women, women with benign breast lesions, and women with breast cancer. The researchers found that the saliva (as well as serum) levels of these markers were significantly higher in women with breast cancer than in healthy women and women with benign breast lesions; they went on to state that the marker may have potential as a tool to diagnose breast cancer or detect recurrence. A separate study reinforces this finding and further suggests that other breast cancer markers (CA15-3) increase while the p53 tumor suppressant protein is reduced in female saliva with breast cancer compared with healthy controls and women with benign breast lesions.
Oral cancer
In 2010 Jou, et al., Found that patients diagnosed with oral squamous cell carcinoma experienced elevated levels of transferrin in saliva compared with healthy control and, moreover, that salivary transferrin measurements using ELISA techniques were "very specific, sensitive, and accurate for early oral cancer detection. "A 2009 study reported that the level of two biomarkers, Cyclin D1 (increased compared with controls) and Maspin (decreased compared to controls), had a 100% sensitivity and specificity for oral cancer detection when measured in saliva. Saliva tests for specific mRNAs have been found to have significant potential for the diagnosis of oral cancer. In fact, there is evidence to suggest that saline RNA diagnosis is slightly superior to serum RNA diagnostics, with a comparative recipient operating characteristic value (ROC) being 95% for saliva but only 88% for serum.
Glucose is dysregulated
A 2009 study compared salivary glucose levels of diabetic patients with non-diabetic control patients. The authors reported that "salivary concentration and excretion [of glucose] was much higher in diabetic patients than in control subjects." In 2009 Rao, et al., Investigates salivary biomarkers that can help identify individual types of diabetes. Researchers found that sixty-five proteins, most of which are involved in regulating metabolism and immune response, are significantly altered in people with type 2 diabetes. They further observed that the relative increase of this specific protein was directly proportional to the severity of the disease (ie, they were somewhat increased in pre-diabetes and significantly increased in diabetics). In 2010 Soell, et al., Determined that one particular salivary biomarker (chromogranin A) was overexpressed in 100% of diabetic patients when compared with controls. In 2010, Qvarnstrom, et al., Performed a cross-sectional analysis of 500 individuals and found that increased salivary lysozyme "was significantly associated with the metabolic syndrome."
Infection condition
Humanity immunodeficiency virus
The accuracy of the anti-HIV salivary antibody test has been demonstrated in various studies; two large-scale studies have recently found the sensitivity and specificity to be 100%. The first was published in 2008 by Zelin et al., And compared antibody and antibody antibody tests using ELISA techniques in 820 individuals. The second study, conducted by Pascoe, et al. Comparing salivary antibody tests with serum antibody tests using ELISA followed by confirmation of Western Blot analysis on 591 individuals. The accuracy of anti-HIV saliva antibody testing has been confirmed by many additional studies, leading to the approval of this method by the U.S. Food & amp; Drug Administration in 2004.
Viral hepatitis
Several studies have shown a diagnostic potential for salivary hepatitis testing. A 2011 study showed that testing of HBV surface antigen saliva using ELISA had a sensitivity and specificity of 93.6% and 92.6%, respectively. Other studies have found that saliva testing for anti-HAV antibodies (IgM and IgG) is an effective method for identifying HAV-infected individuals. Hepatitis C has also been identified using the saliva detection method. Yaari, et al., Reported in 2006 that saliva tests for anti-HCV antibodies resulted in 100% sensitivity and "similar or better" specificity when compared with serum testing.
Parasitic infections
A 2010 study found that detection of saliva-based parasite Entamoeba histolytica was superior to existing fecal detection methods for patients with liver-related E. histolytica liver abscess. In 2004 El Hamshary and Arafa found that anti-E saliva. IgA histolytica concentrations have a "predictive diagnostic value of intestinal amoebiasis... as well as on tissue amoebiasis." A 1990 study involving testing of saliva for E. histolytica in 223 schoolchildren showed sensitivity and specificity of 85% and 98%, respectively. In 2005 Stroehle, et al., Determined that IgG antibody detection of Toxoplasma gondii had a sensitivity and specificity of 98.5% and 100%, respectively. A study published in 1990 demonstrated the diagnostic utility of saliva IgG testing in identifying secondary neurocysticercosis for Taenia solium.
Helicobacter pylori infection
In a 2005 study, researchers investigated the accuracy of the diagnosis of Helicobacter pylori in dyspepsia patients using IgG anti-salivary Hg pylori. They decided that the saliva test for H. pylori antibodies could be used reliably for screening dyspepsia patients in general practice. " In the same year, Tiwari, et al., Examined the accuracy of saliva testing for H. pylori DNA and how well this correlated with the presence of H. pylori was detected through gastric biopsy. Based on their results, the investigators concluded that saliva testing could serve as a reliable non-invasive detection method for H. pylori infection .
Periodontitis
A 2009 study conducted by Koss, et al., Studied salivary biomarkers of periodontal disease; Their findings revealed that three substances (peroxidase, hydroxyproline and calcium) increased significantly in the saliva of patients with periodontitis. A 2010 study found that an increase of three saliva biomarkers (MMP-8, TIMP-1, and ICTP), especially when analyzed using immunofluorometric tests that resolved with time, was suggestive of periodontitis.
Cardiovascular Disease
CRP: salivary biomarker for cardiovascular risk
In 2011 Punyadeera, et al., Studied "the clinical usefulness of salivary C-reactive protein levels in assessing coronary events such as myocardial infarction in primary health care settings." The investigators found that the salivary CRP level in cardiac patients was significantly higher when compared with healthy controls. In addition, they found that salivary CRP correlates with serum CRP in cardiac patients and, thus, could be a useful tool for "large patient screening studies for risk assessment of coronary event."
Nitric Oxide: saliva biomarker for cardio protection
Nitric oxide protective heart is produced in the body by the family of specific enzymes, nitric oxide synthase. An alternative pathway for the formation of nitric oxide is the nitric-nitrite-nitrate oxide pathway in which the inorganic food nitrate is sequentially reduced to nitric oxide. The necessary and compulsory steps in the formation of nitric oxide by the non-nitrite oxide synthase or alternative pathway involve the absorption of nitrate by the salivary glands, the excretion in the saliva, and the subsequent reduction of nitrite by oral commensal bacteria in the mouth.
Salivary nitrites are then chemically reduced in blood and tissue to nitric oxide resulting in decreased blood pressure, inhibition of platelet aggregation, increased cerebral blood flow and flow-mediated dilation, and decreased oxygen costs during exercise. The main source of the inorganic nitrate diet, which is reduced to nitric oxide in the body, comes from leafy green vegetables. Blood pressure that lowers the effects of green vegetables, in particular, spinach and arugula, is abundant in anti-hypertensive diets such as the DASH diet. Several papers have shown that salivary nitrite levels correlate with blood nitrite levels, both of which serve as a meaningful substitute for the effect of lowering blood pressure.
Sobko et al. showed that a traditional Japanese diet rich in leafy vegetables increased plasma and salivary nitrite levels by decreasing blood pressure.
Webb et al. in 2008 reinforced the mandatory role of saliva in humans to produce nitric oxide. Here, they show the consumption of beetroot juice, nitrate rich foods, by healthy volunteers significantly reducing blood pressure and by interfering with saliva, either by spitting or interfering with dietary bioconversion of nitrites to nitrite in the mouth with anti-bacterial mouthwash, chemicals reduction of nitrates to nitrites to nitric oxide with associated deaths in blood pressure subside. By blocking saliva from recirculation or preventing salivary nitrates from being chemically reduced to nitrites, it prevents plasma plasma nitrite levels, and blocks the decrease in blood pressure as well as inhibition of nitric oxide-mediated platelet aggregation confirming the cardio-protective effects of nitric oxide through the conversion of nitrates to nitrite in saliva.
In a series of reports by Ahluwalia and colleagues, they demonstrated in cross protocol over 14 volunteers who digested inorganic nitrate, plasma nitrite and saliva levels increased 3 hours after consumption with a significant drop in blood pressure. The nitrates are extracted from the blood by the salivary glands, accumulating in the saliva, which is then reduced to nitric oxide to have the effect of lowering direct blood pressure. Reduces saliva nitrite in volunteers who already have elevated levels, increased systolic and diastolic blood pressure. Furthermore, prehypertension may be more sensitive to the effect of lowering blood pressure from the nitric-nitrite-nitric oxide food pathway. Monitoring plant-derived bioconversion of nitrates into salivary nitrite serves as a replacement biomarker for total body oxide nitric status.
Allergy condition
A 2002 study explored the relationship between allergies and salivary immunoglobulin levels on eighty subjects. The investigators demonstrated an association between the development of allergies and disorders at specific IgA levels of salivary allergens (increased compared with controls) and total secretory IgA (decreased compared with controls). In 2011 Peeters, et al., Identified characteristic deviations in certain salivary metabolites associated with individuals with peanut allergy when compared to peanut-tolerant controls. In 2003, Vojdani, et al., Found that people exposed to various allergenic fungi and mycotoxins showed "significantly higher salivary IgA antibody levels against one or more fungal species."
Chemical
In 2009 Pink, et al., Reported that the saliva test had become so extensive that it began to replace urine tests as a standard for detecting illegal drugs and prescription drugs. Shin, et al., Reported in 2008 that the detection of saliva ethanol and its three metabolites (methanol, ethylene glycol and diethylene glycol) had "relatively high sensitivity and specificity" and that the test facilitated the rapid diagnosis of alcohol poisoning. A 2002 study showed that there was a good agreement between saliva and breath ethanol analysis, and that salivary chromatographic ethanol test was "specific... [and] showed good accuracy and precision." In 2011 Vindenes, et al., Investigated the feasibility of monitoring drug abuse using saliva, comparing this method with the detection of urine drugs. The researchers found that some drug metabolites were detected more frequently in saliva than in the urine; this applies to 6-monoacetylmorphine, amphetamine, methamphetamine, and N-desmethyldiazepam. The same study shows that saliva testing can detect other drug metabolites, too, although not as frequently as urine testing; this is the case for morphine, other benzodiazepines, marijuana, and cocaine.
Selected critic
Sensitivity and specificity
One of the most frequently cited criticisms of the use of saliva as a diagnostic fluid is that biomarkers are present in an amount too low to be reliably detected. As Wong points out, however, this "is no longer a limitation" due to the increasingly sensitive detection of detection techniques. Advances in ELISA and mass spectrometry, in addition to the emergence of new detection methods that utilize nano technology and other technologies, enable scientists and practitioners to achieve high analytical sensitivity.
The biomarker specificity is another consideration with a saliva test, as well as a blood or urine test. Many non-specific biomarkers (eg, CRP are nonspecific inflammatory markers), and thus they can not be used alone to diagnose certain diseases. This problem is currently being addressed through the identification of some correlative biomarkers of an illness; these can then be filtered together to create a comprehensive test panel that significantly improves diagnostic specificity. Of note, some types of saliva testing are considered by many to be more specific than blood tests; this is especially true for steroid hormones. Because saliva hormone tests only measure hormones that are not bound to sex hormone-binding globulin (SHBG) or albumin, they are considered to represent only the bioactive ("free") fraction. With continued research into the field of saliva testing, accuracy parameters such as sensitivity and specificity will continue to increase.
Standardization
As with other diagnostic testing methods, one disadvantage of saliva testing is the variability that exists between diagnostic tools and laboratory analysis techniques, especially for measuring hormones. Consequently, although the test results may be accurate and reliable in certain test methods or laboratories, it may not be comparative with the test results obtained by using different methods or laboratories. As the research community continues to validate and improve test methods and establish standard diagnostic ranges for various saliva biomarkers, this issue must be resolved. Recently, the National Institutes of Health and the US Public Health Service each provided significant funding for further advances in saliva testing, including the development of sustainable diagnostic standards.
References
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