Oral fluid (OF) tests do not provide reliable information regarding when subjects last consumed cannabis or whether they are under its influence, according to the results of a meta-analysis published in October 2024, in the scientific journal Heliyon. Researchers affiliated with the Canadian Institute for Substance Use Research at the University of Victoria in British Columbia assessed data from seven studies involving 116 subjects.
They reported that OF tests frequently produced disparate results, even when subjects consume similar quantities of cannabis. “Research shows a high degree of variability in THC concentrations for subjects given the same amount of cannabis”, investigators reported. “This variability produced some very high outliers in terms of THC concentrations and detracts from OF tests as a valid tool”.
Researchers further acknowledged that subjects who inhale cannabis are far more likely to test positive on oral fluid tests as compared to those who orally ingest infused products. They also acknowledged that some subjects can test positive past cannabis exposure for more than 24 hours after smoking.
“We conclude from our meta-analysis that validity is not ideal for either detection of prior use or impairment at a commonly used THC cut-off of 1 ng/mL”, wrote the study’s authors. “OF tests should not be considered a valid indicator of [cannabis-induced] impairment”.
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25 May, 2025