Dear Ms. Swarbrick,
RE: The efficacy of cannabis testing using oral fluid samples
As an individual deeply involved in drug and alcohol impairment detection, I was surprised and very disappointed in the views you expressed during your recent interview with Jack Tame on the topic of cannabis law reform. From a technical and fact based perspective, I must question the assertions made with regards to ‘impairment testing’ and the claimed unreliability of what I am guessing was oral fluid (saliva) testing for cannabis. You stated a 14% false rate and that this made it unreliable. Both of these statistics are untrue.
While I recognise that urine testing for cannabis – or, more correctly, cannabis metabolites - is poor and has no relationship to judging or determining impairment, the same cannot be said for oral fluid drug testing using the recent Standards.
Impairment tests are, as you correctly noted, a physical ‘sobriety’-type test. They can be poor and extremely subjective, and as a consequence they are not recommended best practice for either roadside or workplace testing.
But what you failed to adequately evaluate and convey is that there is an oral fluid test that is reliable, verified, validated and instrument based that can be and is reliable. Furthermore, this test falls within the new NZ Standards guidelines and is therefore an objective measure of potential intoxication in much the same way as the accepted measure of potential alcohol impairment is measured in micrograms of alcohol per litre of breath.
Moreover, this oral fluid test is used all over the world at various cut-off concentrations suggested by country-relevant standards. It is therefore a reliable and excellent indicator (screen) of likely impairment or otherwise.
As with any test that isn’t negative, the oral fluid test (following the new NZ Standards) uses THC (tetrahydrocannabinol – the active ingredient in cannabis) cut-off concentrations that consider ‘acute impairment’ and are therefore an indicator of those likely to be impaired.
Any individual who fails an onsite or roadside screen drug test is required to be confirmed by a laboratory as standard practice to identify unequivocally presence of the drug compound, with the levels thus identified being linked to acute impairment. This is the same way that a roadside screen test for breath alcohol may lead to samples of blood being taken and analysed.
I am disappointed you haven’t researched this better and that you appear to have based your opinions on oral fluid drug testing on outdated information.
There is more recent science, there are more recent and accepted technologies in use for cannabis testing, and these technologies are being used around the world to identify, detain and prosecute if proven impaired drivers.
This process directly addresses the scourge of ‘drugged drivers’ – a scourge which has cost Karen Dow her son and Logan Porteous his parents.
With cannabis law reform underway, cannabis could in the near future conceivably fall into the same category as alcohol: legal, but not in all circumstances. Defined levels of alcohol impairment are prohibited for drivers and in workplaces. It is sensible to similarly set boundaries for cannabis – and these are already identified in AS/NZS4760:20190.
I am happy to engage further with you to present the facts around verified, validated, reliable cannabis screening using oral fluid. This testing is crucial in support of safer workplaces, better policing and healthier communities in New Zealand, particularly with cannabis law reform prominent in the public consciousness.