Saliva Testing: The Shift to Saliva in Sample Testing

Saliva testing is a common method of detecting the presence of various markers in the body, including hormones and drugs.¹ Research shows that oral fluid, or saliva, is a promising specimen for drug screening and has several key advantages over other testing specimens.² This article will examine the advances in and benefits of saliva testing, and how it compares to urine and hair testing. We’ll also discuss the various applications of saliva testing, from the workplace to the sports field to the forensics lab.

The limitations of hair and urine testing

Hair testing:

Hair testing can detect exposure to psychoactive substances within long time frames – much longer than those of urine and saliva testing. However, hair testing cannot detect very recent drug use, and it’s especially difficult to detect infrequent use of cannabis/marijuana with a hair sample.³ 

Despite their extended detection period (up to 90 days), hair samples can’t be tested onsite, which means a delay in test results.⁴

Hair samples are also subject to many variables, including color, race, condition (the use of bleach or dye) and growth rate. If testers don’t account for all of these variables, they may get false-positive or false-negative results.⁵

Urine testing:

Urine specimens are susceptible to tampering via dilution or adulteration. And, of course, observing urine collection to reduce sample tampering is an invasive process.⁴

Urine-drug levels don’t provide any interpretive data (e.g. about the dose used.)⁴

Urine is an unstable fluid that changes composition as soon as it leaves the body.⁶ Light, temperature, pH, certain foods, prescription drugs and preservatives can all affect the results of a urine sample analysis.⁶ The concentration of drugs in urine can also be influenced by fluid intake.⁴

Benefits and advancements of saliva testing

Saliva testing benefits:

• Saliva samples can be collected easily, non-invasively and under direct supervision.²
  
• Multiple specimens can easily be collected from the same person, at the optimum times for the diagnostic information needed.¹
• Saliva can be collected at home or in remote sites by unskilled personnel and, with the use of the right collection devices, it can remain stable at ambient temperatures for several weeks.¹
• Saliva collection is safer than blood collection. There is no need for sharps and the concentration of antigens in saliva is low, meaning the tester’s risk of contracting HIV and hepatitis infections is significantly lower compared to blood tests.
• Saliva drug tests can be easily processed using conventional drug screening and confirmation methods.²
• Saliva can be tested onsite for rapid results.⁵
• Saliva testing is more economical than hair testing, and often more economical than urine and blood testing.⁷

Salivary Glands

Saliva testing advancements:

In the past, a major barrier to using saliva as a diagnostic fluid was the fact that many informative analytes are present in saliva in low amounts. With new, highly sensitive technologies, these low analyte levels are no longer a limitation. Saliva has been reliably used to detect HIV-1 and -2, and viral hepatitis A, B and C. It can also be used for drug screening and monitoring. Today, nearly any substance that can be measured in blood can also be measured in saliva.⁸

In recent years, a notable use of saliva testing has been COVID testing. Saliva tests were shown to have a very good discriminative and diagnostic ability to detect SARS‐CoV‐2, with high specificity and sensitivity.⁹

The applications of saliva testing

Workplace settings:

In some countries, employers may use saliva testing for pre-employment drug screens, random drug testing, reasonable-suspicion drug tests and post-accident screens.¹⁰

Law enforcement:

Roadside oral fluid testing is gaining popularity as a way to identify motorists driving under the influence of drugs.^11,12

Clinical settings:

Saliva drug tests may be used to monitor compliance/abstinence in patients in drug rehabilitation care.¹²

Testing for drugs of abuse:

Saliva drug tests can detect the presence of drugs such as marijuana, cocaine and alcohol.⁷ Like blood testing, saliva testing can be used to determine pharmacokinetic parameters and may correlate with impairment.¹²

Diabetes:

Research shows that salivary glucose monitoring is a reliable method for monitoring diabetes. It’s a painless, non-invasive alternative to blood glucose monitoring.¹³

Forensics:

After blood, saliva is the second-most common biological evidence found at any crime scene. In forensics, saliva can be used as biological evidence and can provide information about an individual such as sex, blood group, microbial signature, biomarkers and even habits like smoking.¹⁴

Get in touch with Medix Biochemica to access a wide variety of quality biospecimens for IVD assay development 

Future trends in saliva testing

Testing for banned substances in sport:

Ongoing studies are taking place in the field of saliva testing for the detection of banned substances in sport. As these tests become more convenient, reliable and available, agencies such as the World Anti-Doping Agency (WADA) could potentially incorporate saliva testing into their programs.⁷

An in-field study on the use of saliva for anti-doping showed that oral fluid analysis was simple and efficient, and drug findings in these samples correlated reasonably well with those in matched urine samples. Read more.¹⁵

A pilot study by the University of Ghent in Belgium explored the potential for steroid profiling in saliva and compared the outcome with urinary analysis for future implementation in routine anti-doping screening. Read more.¹⁶

Chemists in the University of Waterloo’s Faculty of Science have developed a revolutionary saliva test that could be a faster and more affordable alternative to urine tests. The test uses a specially coated sampling device designed to sit under the tongue for five minutes. Read more.¹⁷

Integration with wearable technology:

Saliva-based wearable devices, e.g. glucose pacifier sensors, enable the user-friendly, painless and continuous monitoring of multiple biomarkers. One example is illustrated below.¹⁸

Figure 1: (A) Overview of the glucose pacifier sensor. Photograph of the pacifier utilization and real-time accessing of glucose signal from saliva, graphical representation of Pacifier modules assembled with wireless electronics (b), and schematic design of glucose enzymatic approach on the PB transducer (c). (B) The on-body glucose monitoring is schematic after 30 min of saliva collection and the on-body chronoamperometric response of a stable enzymatic sensor of a diabetic patient before and after meals (a-f) with and without enzyme control. (Garcia-Carmona, 2019)^18b

Neurology:

Studies are underway to investigate the usefulness of measuring salivary noncoding RNA (ncRNA) levels as a way to accurately diagnose mild traumatic brain injury (TBI) and post-concussion syndrome (PCS).^19,20 Unique diagnostic signatures of concussion have been found in the saliva of male athletes diagnosed with concussion. Read more.²¹

Saliva testing is also gaining interest as a promising source of biomarkers for detecting neurodegenerative diseases, such as Alzheimer’s, Parkinson’s and Huntington’s. In addition, these biomarkers have the potential to assess the efficacy of novel therapies for these illnesses.²²

Cancer detection:

Saliva in vitro diagnostic (IVD) testing may also be useful as a non-invasive, inexpensive way to detect certain cancers, including lung cancer, breast cancer and pancreatic cancer.²³

Sports science:

Salivary biomarkers can be measured to assess the impact of strenuous physical activity and recovery,^24,25 e.g. cortisol levels can be assessed to measure exercise-induced stress.²⁶ Salivary testing can also be used to assess hydration status.²⁷

In conclusion, saliva testing is a practical, non-invasive testing method with applications that range from simple saliva drug tests to the diagnosis and management of serious illnesses. The interest in salivary testing continues to grow as its reliability becomes more established.

Are you looking for a reliable IVD raw materials provider for your saliva test development? Our wide offerings include saliva biospecimens as well as a number of other infectious and drug of abuse-related antibodies and antigens.

Get in touch with the expert team at Medix Biochemica to discuss your requirements.

References:

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   1b Salivary glands: function, location & anatomy. Cleveland Clinic. Accessed August 15, 2024. https://my.clevelandclinic.org/health/body/23462-salivary-glands.
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10. States explore oral fluid testing to combat impaired driving. Accessed August 14, 2024. https://www.ncsl.org/transportation/states-explore-oral-fluid-testing-to-combat-impaired-driving.
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    15b García-Carmona L, Martín A, Sempionatto JR, et al. Pacifier biosensor: toward noninvasive saliva biomarker monitoring. Anal Chem. 2019;91(21):13883-13891. doi:10.1021/acs.analchem.9b03379.
16. Hicks SD, Onks C, Kim RY, et al. Diagnosing mild traumatic brain injury using saliva RNA compared to cognitive and balance testing. Clin Transl Med. 2020;10(6):e197. doi:10.1002/ctm2.197.
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18. Pietro VD, O’Halloran P, Watson CN, et al. Unique diagnostic signatures of concussion in the saliva of male athletes: The Study of Concussion in Rugby Union through MicroRNAs (Scrum). Br J Sports Med. 2021;55(24):1395-1404. doi:10.1136/bjsports-2020-103274.
19. Jiao LL, Dong HL, Liu MM, et al. The potential roles of salivary biomarkers in neurodegenerative diseases. Neurobiol. Dis. 2024;193:106442. doi:10.1016/j.nbd.2024.106442.
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21. Neves RS, da Silva MAR, de Rezende MAC, et al. Salivary markers responses in the post-exercise and recovery period: A systematic review. Sports. 2023;11(7):137. doi:10.3390/sports11070137.
22. Borchers J, Merle CL, Schöneborn DD, et al. Salivary diagnostic for monitoring strenuous exercise-A pilot study in a cohort of male ultramarathon runners. Int J Environ Res Public Health. 2022;19(23):16110. doi:10.3390/ijerph192316110.
23. Tsunekawa K, Shoho Y, Ushiki K, et al. Assessment of exercise-induced stress via automated measurement of salivary cortisol concentrations and the testosterone-to-cortisol ratio: A preliminary study. Sci Rep. 2023;13(1):14532. doi:10.1038/s41598-023-41620-5.
24. Chen CH, Lu YP, Lee AT, et al. A portable biodevice to monitor salivary conductivity for the rapid assessment of fluid status. J Pers Med. 2021;11(6):577. doi:10.3390/jpm11060577.
25. Ligtenberg AJM, Brand HS, van den Keijbus PAM, et al. The effect of physical exercise on salivary secretion of MUC5B, amylase and lysozyme. Arch. Oral Biol. 2015;60(11):1639-1644. doi:10.1016/j.archoralbio.2015.07.012.