One of the main advantages of oral fluid drug tests is that they are relatively quick and easy to collect – for example, there is no need for special collection facilities. Also, the direct observation reduces the potential for adulteration which is known to occur during urine drug testing, including substitution, dilution or the mixing in of chemicals (Wong, Tran, & Tung, 2005).
Oral fluid drug tests can pick up more recent drug use. For example, if a worker has smoked cannabis a few minutes prior to the test, it is likely to produce a ‘non-negative’ test result in a saliva test, however, the cannabinoid is likely not detected in a urine sample as it is not yet metabolised in the body – it would only be detectable in urine after several hours.
Therefore, the argument often arises that saliva tests are the better option when assessing impairment (i.e. post-accident). However, research has shown that oral fluid drug tests have a lower probability of detecting cannabis, codeine and amphetamine use compared to urine drug tests (Casolin, 2016; Huestis, 2011), challenging the notion that they are better measures of impairment. Researchers therefore recommend employers conduct a saliva test for post-accident testing and have it followed up by a urine test when assessing for impairment (Casolin, 2016).
Overall, immunoassays (e.g. saliva and urine drug tests) have weaknesses which can result in false-positives and false-negatives. Furthermore, the ability to test for designer drugs (e.g. synthetic cannabinoids) is challenging. Therefore, please remember: Every on-site ‘non-negative’ test result must be sent for confirmatory testing in a lab!
To learn more, we cover all of the pro’s, con’s and how to carry out drug testing in our workplace drug and alcohol testing training course.
- Casolin, (2016). Comparison of Urine and Oral Fluid for Workplace Drug Testing. Journal Anal Toxicology, 40(7), 479-485.
- Huestis, (2011). Oral fluid testing: Promises and pitfalls. (Q&A). Clinical Chemistry, 57(6), 805-10.
- Wong, Tran, & Tung, (2005). Oral fluid drug tests: Effects of adulterants and foodstuffs. Forensic Science International, 150(2), 175-180.