THC saliva test: 15 ng/mL or 50 ng/mL, what’s the difference?
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What does the threshold of a saliva test mean?
The detection threshold is the concentration from which the device is designed to produce a positive result. The lower this threshold, the more sensitive the test is to low concentrations of the targeted substance.
For the same molecule, a THC test at 15 ng/mL can detect a concentration between 15 and 49 ng/mL, while a 50 ng/mL test may remain negative in this range. This does not mean the first test is automatically better in all contexts: it must also be properly validated, stored, and used according to its instructions.
More sensitive threshold, consistent with the minimum threshold set in France for roadside salivary THC screening.
Less sensitive threshold for THC. It may meet other specifications but does not correspond to the French minimum threshold for roadside screening.
What the French decree of December 13, 2016 provides
For salivary screening tests conducted under the Highway Code, the decree sets the following minimum thresholds:
- THC: 15 ng/mL of saliva;
- amphetamine, methamphetamine, and MDMA: 50 ng/mL;
- cocaine or benzoylecgonine: 10 ng/mL;
- morphine and 6-monoacetylmorphine: 10 ng/mL.
15 ng/mL is not an "authorized level"
The regulatory threshold describes the minimum performance of the screening device. It does not create a THC amount below which driving would be allowed. In France, the offense is based on driving after drug use established by the analysis provided by the procedure.
Is a 15 ng/mL test identical to the one used by the police or gendarmerie?
Not necessarily. Two devices can display the same threshold while differing in design, substance panel, validation, reading method, and performance. It is therefore preferable to speak of a threshold consistent with the French roadside framework, without claiming that a commercial product is exactly the same as the one used during a check.
How to choose a salivary THC test?
- verify that the targeted molecule is indeed delta-9-THC;
- check the announced threshold and the manufacturer's performance data;
- verify the applicable CE marking, instructions, and shelf life;
- respect the time without drinking, eating, or smoking indicated before sampling;
- interpret the result as an indication, never as a driving authorization.
The Drugdiag® Saliva THC test offered by AMA Prévention targets THC with an announced threshold of 15 ng/mL and a shelf life of 24 months.
Discover the 15 ng/mL salivary THC test
