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.
| Did you know? In adults, the salivary glands produce 1L to 2L of saliva a day. Just one drop of saliva contains a sample of an individual’s complete genetic makeup.1b |
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 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
| Did you know? Saliva is composed of 99% water. The remaining 1% is made up of proteins, enzymes, mucus and buffering agents.1b |
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
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
Roadside oral fluid testing is gaining popularity as a way to identify motorists driving under the influence of drugs.11,12
Saliva drug tests may be used to monitor compliance/abstinence in patients in drug rehabilitation care.12
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
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
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
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
| “Our findings provide support for previous suggestions that anti-doping laboratories use OF (oral fluid), and to some degree EB (exhaled breath), as matrices for detecting recent use of stimulants, beta-blockers, and cannabinoids.” - Miller et al. 2019.15 |
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
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
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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
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
| “As saliva contains a wide range of biomolecules that are indicative of various physiological processes, such as hormones, proteins, and microRNAs, several salivary molecules, including S10OB, neurofilament light chain (NfL), microRNAs, and exosome vesicle proteins, have been found to be associated with mild TBIs and PCS.” - Mavroudis et al. 2023.17 |
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
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
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
| Did you know? Moderate to high-intensity exercise increases saliva flow rate and also increases the levels of certain salivary proteins.28 |
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.
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