Study Results Show CBN Can Produce False Positive For THC In Drug Screen

A new study from the University of Utah Health Sciences Center in Salt Lake City, Utah has demonstrated that cannabinol (CBN) can produce a false positive for tetrahydrocannabinol (THC) in immunoassay screenings, the most common type of drug test.

CBN is a mildly psychoactive metabolite of THC that has gained some popularity as a natural sleep aid.

Led by Grace Kroner, PhD, the research team behind the study added 1,000 ng/mL of CBD and CBN to three separate batches of clean urine in addition to cannabichromene (CBC) and cannabigerol (CBG) which were added at the same concentrations.

Researchers then tested the samples using Microgenics Multigent Cannabinoids and Beckman Coulter Emit II Plus Cannabinoid tests.

While CBD, CBC, and CBG failed to produce a positive on either of the tests, CBN showed up on the Emit II test as THC.

Upon further investigation, researchers found that it only took 100nl/mL of CBN to trigger a THC-positive result on the Emit II.

“These findings will help interpreting drug screening immunoassay results,” said Kroner. “If physicians and laboratorians know a patient is taking CBN, they can consider that they get a positive result that it’s not due to pure CBD oil alone. These results are always assay dependent, so the field needs to keep this in mind.”

In addition to showing that CBN show up as THC in a drug screen, the study highlights a need for manufacturers and healthcare institutes to evaluate the cross-reactivity of their tests to protect patients and others from false positive tests.

Results from the study were presented on Monday at the 71st AACC Annual Scientific Meeting & Clinical Lab Expo in Anaheim, California.