Substance testing strips do not test for all drugs

May 19, 2023

According to a recent statement released by Health Canada, illicit drug test strips sold to test substances may not have the efficacy consumers expect. These tests are not the same as those which are used to test a person’s urine to ascertain what drugs they have taken in. Drug tests for urine are considered medical devices and must go through extensive testing by Health Canada to be approved, after they have confirmed their safety, quality and effectiveness. This process is very different for test strips which are meant for testing substances to identify what is in them, which are sold as consumer products and are not reviewed by Health Canada in the same way. 

“No test is 100 per cent effective at detecting all potentially dangerous substances in illegal drugs. A false negative could result in a fatal overdose. Treat all illegal drugs as though they are potentially contaminated with unknown and dangerous substances,” said the statement.

In addition, the statement noted that drug-testing strips sold online or in stores as consumer products may not have been evaluated by the federal government for evidence of effectiveness.

In his interview with Global News, Dr. Daniel Werb, associate health policy professor at the University of Toronto, said test strips are most commonly used to detect fentanyl, with an accuracy of finding a presence of less than 5% of the total composition, which can be fatal.

Furthermore, Dr. Werb added that this is a higher level of detection than infrared spectrometry technologies used by clinics to test drugs, which can detect a broader range of drugs present but not a presence below 5%.

“The whole idea around fentanyl test strips is that they’re able to detect fentanyl when it’s present at very low concentrations,” said Dr. Werb.

As well, Health Canada statement reminds readers that the test strips may not be able to detect other lethal drugs as new drugs are entering the drug supply, including the animal tranquilizer xylazine. Consumers must pay attention to the drugs which are listed on the test strip as being included. Not all substance testing strips test for all drugs. 

“Our understanding was that most folks in Toronto were not choosing to use xylazine, it was just kind of being cut into their drugs unknowingly. So it certainly is a problem,” said Karen McDonald, the lead for Toronto’s Drug Checking Service, in her interview with Global News.

What’s more, xylazine can depress nervous system function and does not respond to naloxone, a life-saving drug used to reverse the effects of opioid overdose.  

Health Canada also stated it is working with companies to include warnings on the packages of test strips in order to inform consumers to be aware of the limitations of the test.

It’s really important that people understand what (the test’s limitations) are,” said Sam Tobias, a research assistant at the University of British Columbia specializing in drug supply. “Then take those limitations and sort of interpret what the results mean in the context of those limitations.”