How accurate are oral fluid drug tests?

By Work Place | Last updated: January 16, 2019

Oral fluid drug tests that employ laboratory-based analysis are considered to be highly accurate. The concentrations of substances detected in oral fluids correlate strongly with those present in blood. In fact, the accuracy of oral fluid drug tests is comparable to, or greater than, that of urine drug tests. Though not yet permitted for testing conducted according to the Substance Abuse and Mental Health Services Administration (SAMHSA) Mandatory Guidelines for Federal Workplace Drug Testing Programs, oral fluid testing has gained wide acceptance in the private sector, and is used for criminal justice related testing. However, in May of 2015, the U.S. government announced plans for the future inclusion of oral fluid drug testing procedures in the SAMHSA Mandatory Guidelines. In recent years, an increasing number of manufacturers have obtained FDA clearance for point-of-collection (POC) oral fluid drug testing devices. Currently, the accuracy of THC detection on a POC oral fluid test is not capable of detecting to the level equivalent of lab testing.

What is an Oral Fluid Drug Test?

Laboratory-based oral fluid drug testing, also known as saliva testing, uses a two-step process to evaluate an oral fluid specimen. The saliva is first tested using drug-specific enzyme immunoassay (ELISA). If a positive result is detected, a confirmation test is conducted using either gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). These chromatographic tests separate substances at a molecular level, which allows highly specific identification of the contents of a test specimen.

Can I Get a False Positive on an Oral Fluid Drug Test?

As with urine samples, some over-the-counter or prescription drugs may cause a positive result during the initial oral fluid screening test using immunoassay technology due to cross-reactivity. The confirmation test using GC/MS or LC/MS/MS eliminates false positives triggered by cross-reactions.

POC oral fluid drug tests that provide immediate on-site results employ only a self-contained immunoassay analysis. These tests are usually less sensitive than laboratory-based tests. Results from POC oral fluid tests have proven to be variable and are thus not considered as reliable or accurate as their lab-based counterparts.

Several factors may influence the accuracy of any single oral fluid drug test. Collection procedures, the condition of the sample, and the analysis criteria used will all affect the accuracy of the test.

How Does Oral Fluid Drug Testing Work?

Oral fluid drug testing works by collecting a sample of the saliva from the mouth of the test subject. Samples are collected either using an absorbent swab or pad, or by forced expectorant (spit). Most collection devices incorporate a display that indicates when a sufficient sample amount has been collected. An inadequate sample amount will render the specimen invalid for testing. When expectorant collection methods are used, the sample is more viscous and may have food and other contaminants that must be removed before lab testing. This process may reduce the drug concentration of the sample.

The buffering agent used with a specific collection device and the temperature at which the sample is maintained may also affect accuracy. Because of its unique composition, TCH is particularly subject to difficulty in sample collection and handling. In rare instances, foods, beverages, or other substances ingested immediately prior to an oral fluid test may adulterate a sample. However, these effects are short-lived and are for the most part eliminated by proper collection procedures.

While any drug test may be subject to external factors that affect its accuracy and validity, laboratory-based oral fluid drug testing is considered to be an accurate means of assessing an individual's exposure to drugs of abuse.

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