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Federally Funded Study Enhances Marijuana Screening Procedure To Detect THC In Blood



Amid broad calls for better tests to screen for marijuana use, researchers behind a federally funded study say they have developed new procedures to enhance the selectivity of a popular forensic testing method, allowing better detection of delta-9 THC and its metabolites in blood.

The new 107-page report by researchers at the Virginia Department of Forensic Science (DFS) is the product of a roughly $290,000 grant awarded in 2020 by the National Institute of Justice (NIJ), a division of the Department of Justice (DOJ). The goal of that funding, according to an award description, was to “develop and validate an automated sample preparation technique for the quantitative evaluation of an expanded cannabinoid panel (CBD, CBN, THC, THC-A, CBD) in biological matrices.”

The award was part of a pool of nearly $1.2 million in federal funding for a program intended “to direct the findings of the research and evaluation toward the identification of the most efficient, accurate, reliable, and cost-effective methods for the identification, analysis, and interpretation of physical evidence for criminal justice purposes.”

“The ever-changing climate of cannabis decriminalization and/or legalization has significantly impacted forensic laboratories and is anticipated to increase the caseload in forensic toxicology,” the federal agency said in the award description. “In addition, products claiming to contain other cannabinoids, including cannabidiol [CBD] and tetrahydrocannabinolic acid [THC-A], have become widely available.”

The project, the grant description says, “will allow for DFS and other forensic toxicology laboratories to adapt to the evolving cannabis industry by expanding cannabinoid testing capabilities.”

Rebecca Wagner, the chemistry research section supervisor at Virginia DFS who served as lead author of the new report, explained the goal of the research in an email to Marijuana Moment.

“The focus of the project was to develop and validate a method capable of separating and uniquely identifying Δ9-tetrahydrocannbinol (active component in marijuana) from other tetrahydrocannabinol isomers in antemortem blood and postmortem blood specimens,” Wagner wrote. “The method includes the confirmation and quantitation of Δ9-tetrahydrocannbinol and its metabolites.”

The Virginia agency was awarded a separate grant last year of more than $441,000 to develop better tools for analyzing psychedelics in biological samples.

The federal government also funded separate recently published research identifying a promising new method to test for recent marijuana use. That study, funded in part by the National Institute on Drug Abuse (NIDA), determined that more accurate method of testing than currently used is by analyzing the molar metabolite ratio of THC to THC-COOH in the blood. Those findings could have key criminal justice implications, as police now rely on more basic, often unreliable blood tests for evidence of possible impairment.

The new DFS research, published last month, explains the technical details of a process developed “using a supported liquid extraction with dual column LCMSMS [liquid chromatography with tandem mass spectrometry] analysis” to identify cannabinoids in blood and urine.

“The methodology employed LCMSMS with two analytical columns of different stationary phases to enhance the confirmation of cannabinoids,” the study says. “Two methods (quantitative and qualitative) were validated in accordance with ANSI/ASB 036) 036, Standard Practices for Method Validation in Forensic Toxicology.”

There were some limitations to the outcomes, the study said. For example, delta-8 THC “should be qualitative only”—not used for measuring the actual level of the cannabinoid, authors noted. The same goes for “evaluation of cannabinoids in urine” as well as evaluation for CBD.

The research is part of a growing call for more precise and reliable ways to measure recent marijuana use and impairment—often around driving—as more jurisdictions legalize the drug. Last summer, a congressional report for a Transportation, Housing and Urban Development, and Related Agencies (THUD) bill said that the House Appropriations Committee “continues to support the development of an objective standard to measure marijuana impairment and a related field sobriety test to ensure highway safety.”

Sen. John Hickenlooper (D-CO) sent a letter to the Department of Transportation (DOT) in 2022 seeking an update on that status of a federal report into research barriers that are inhibiting the development of a standardized test for marijuana impairment on the roads. The department was required to complete the report by November under a large-scale infrastructure bill that President Joe Biden signed, but it missed that deadline and it’s unclear how much longer it will take.

A study published in 2019 concluded that those who drive at the legal THC limit—which is typically between two to five nanograms of THC per milliliter of blood—were not statistically more likely to be involved in an accident compared to people who haven’t used marijuana.

Separately, the Congressional Research Service in 2019 determined that while “marijuana consumption can affect a person’s response times and motor performance … studies of the impact of marijuana consumption on a driver’s risk of being involved in a crash have produced conflicting results, with some studies finding little or no increased risk of a crash from marijuana usage.”

Another study from 2022 found that smoking CBD-rich marijuana had “no significant impact” on driving ability, despite the fact that all study participants exceeded the per se limit for THC in their blood.

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Ben Adlin, a senior editor at Marijuana Moment, has been covering cannabis and other drug policy issues professionally since 2011. He was previously a senior news editor at Leafly, an associate editor at the Los Angeles Daily Journal and a Coro Fellow in Public Affairs. He lives in Washington State.


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