"Results from samples expected to be stimulants were divergent between testing groups. Crystal methamphetamine samples tested using take-home drug checking were reported as fentanyl positive more often than on-site samples (27.6% vs. 5.2%). The same pattern was seen for cocaine samples tested using take-home drug checking (17.2% vs. 1.1%). However, the study was underpowered to evaluate equivalence between these testing groups. A small portion of the test strips (3.8%) yielded an unclear or illegible response. It is unclear what the participants did in these cases, but the inclusion of multiple test strips would have allowed for repeat testing.
"Notably, when the results of take-home drug checking were stratified based on previous experience with fentanyl test strips, there was a trend towards a smaller difference between the results of take-home drug checking and on-site drug checking. For opioids, when only results from those who were using fentanyl test strips for the first time were included, there was a difference of 1.6% between take-home drug checking and on-site drug checking. This difference was reduced to 0.6% when only including samples from those who had self-reported prior experience with using fentanyl test strips. Similar results were seen for crystal methamphetamine (28.9% to 15.2%) and cocaine (28.3% to 7.8%)."
Klaire, S., Janssen, R. M., Olson, K., Bridgeman, J., Korol, E. E., Chu, T., Ghafari, C., Sabeti, S., Buxton, J. A., & Lysyshyn, M. (2022). Take-home drug checking as a novel harm reduction strategy in British Columbia, Canada. The International journal on drug policy, 106, 103741. doi.org/10.1016/j.drugpo.2022.103741