Accurate Drug Testing for Marijuana is Not Possible With Oral Fluid Point of Collection Testing Devices

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5 September 2023

Accurate Drug Testing for Marijuana is Not Possible With Oral Fluid Point of Collection Testing Devices

Oral fluid testing is becoming a more popular method of testing for illegal drugs and controlled substances for the simple facts that this method of testing makes it more difficult to adulterate and the timelines of a positive test more closely relates to impairment levels than urine testing results. Recently, there has been significant push from some companies to use point of collection, or instant oral fluid, testing. However, the sad truth is a lot of these claims are either false or very misleading in many cases. Point of collection oral fluid tests simply do not work properly for marijuana testing.

How Point of Collection Tests Work

To understand why this type of testing does not work well for marijuana, we need to have a baseline understanding of how a point of collection test works. In its most basic form, this test is similar to fluid wicking up a strip of litmus paper. At one end there is a foam type collection pad that is connected to the litmus paper. Once enough oral fluid sample is on the collection pad, the oral fluid moves up the paper and reacts with the antigens on the paper in order to perform the test. The problem with the THC molecule (the active ingredient in marijuana) that is tested for in oral fluid is it is a “sticky” molecule. Basically, it does not wick up the testing device like other drug molecules. Because of this, the tests are unable to test concentrations at the low levels needed to be an effective test.

Concentration Requirement Standards

The cutoff concentration listed in Draft#3 recommended concentration for oral fluid from SAMHSA (for the United States), The Canadian Model, and the ENFORM Alcohol and Drug Policy Model for the Canadian Upstream Petroleum Industry is 4 ng/mL for screening tests and 2ng/mL for confirmation. These levels were originally set by SAMHSA, the Canadian Model and ENFORM then followed their lead. This means that the point of collection device must be able to test levels as low as 4 ng/mL. Currently there is not a device on the market that can come even close to testing at those concentrations of THC.

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Average Marijuana Levels After Use

How did they come to this level? Also, at this level, how long will the drug be in the oral fluid? Both are good questions that require some explanation. There have been several studies to track the amount of THC in oral fluid in both active smokers and in passive subjects (second hand smoke) over various amounts of time. The goal of the cutoff concentration is to have active smokers return a positive and passive subjects return a negative result during testing. In one study, 4 active smokers and 4 passive subjects were studied while confined in a van (yes, a van). The tests were performed on a chemistry analyzer in a lab and confirmed by GC/MS/MS. At no time were the passive subjects above the cutoff of 4 ng/mL. In fact, the highest level they attained was 0.8 ng/mL. As for the active smokers, their levels peaked just minutes after smoking at an average of 148 ng/mL, but dropped quickly to an average of 32 ng/mL at 30 minutes after smoking, and 13.8 ng/mL at one hour after smoking. They remained above the 4 ng/mL until 4 hours had passed. Habitual users will test above the 4 ng/mL longer than the 4 hours that study as more THC builds in their system over time. Most collection testing devices have a cutoff concentration of 25 ng/mL or above, well above the 4ng/ML level for a non-habitual user just 4 hours after exposure. Projecting from the data in that study, it is clear that a non-habitual offender would only show a positive result for about 45 minutes or less after ingestion.

Collection Test Marketing Claim Myths

  • The device is FDA and/or Health Canada cleared
    FDA (U.S.) and Health Canada clearances are a good thing for a testing device. This tells us that the tests have research validating that the device works as claimed. The problem with this is that most of the devices on the market have a THC cutoff concentration of 25 ng/mL or above, practically useless for THC testing. As a note, there are currently no POCT oral fluid devices with FDA clearance, and only 2 brands with Health Canada clearance.
  • “Aligns to required classes in COAA and ENFORM testing models”
    Basically, this is just saying that it tests for all of the drugs listed in the Canadian model, or the ENFORM model. The device tests for marijuana, cocaine, amphetamines, methamphetamines, opiates, and PCP. This does not make any claim as to the testing concentrations of the device. It does not mean that the device tests at the cutoff concentrations that are required for these models, just that it tests for the drugs.

Recommended Alternative Testing

My recommendation for oral fluid testing is to perform a lab based test. At this point in time there are no point of collection devices on the market that meet the cutoff concentrations for THC using any of the industry accepted standards listed above. The only way to get a valid oral fluid test for THC is to perform a lab based test where the laboratory instruments are capable of much more sensitive levels testing.