Evaluation of the Canadian approved drug screening equipment cut-off levels for tetrahydrocannabinol (THC)
Bibliographic record
Abstract
In 2018, Canada introduced roadside oral fluid (OF) screening devices, called Approved Drug Screening Equipment (ADSE), as an investigative tool in impaired driving investigations to detect tetrahydrocannabinol (THC), cocaine and/or methamphetamine in drivers. In this work, we compare the detection and concentration of THC in blood samples collected from suspected impaired drivers that tested positive at the roadside for THC on an ADSE. The two ADSEs that were utilized were the Dräger DrugTest® 5000 (DDT) and the Abbott SoToxa™ (SoToxa), both configured with a THC OF concentration cut-off concentration of 25 ng/mL. Blood samples were screened for cannabinoids using immunoassay and positive results were followed up by confirmation/quantitation of THC by ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS-MS). A total of 230 cases were available where a blood sample was collected from a suspected impaired driver subsequent to a positive THC screen result on an ADSE. The blood samples were taken an average of 1.4 hours (range = 9 minutes to 3.2 hours) after the ADSE test. THC was confirmed in 98% of blood samples with concentrations across all samples ranging from not detected (cut = off 0.5 ng/mL) to greater than 20 ng/mL. Further, 90% of the blood samples had a THC concentration of 2.0 ng/mL (the lower per se limit in Canada) or greater. A positive ADSE test of a suspected impaired driver may predict that the driver has a detectable level of THC in their blood, and there is a high likelihood that the THC blood concentration is 2.0 ng/mL or higher. Hence, ADSE may be a useful tool for law enforcement and aid in the development of grounds to believe that a driver is operating a conveyance with a THC concentration exceeding Canadian per se limits.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.009 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".