Urine drug screening for early detection of unwitting use of fentanyl and its analogues among people who inject heroin in Sydney, Australia.

These negative findings contrast sharply with similar Canadian studies. While no cases of fentanyl-laced heroin use have been detected so far, we have demonstrated that this surveillance design is low-cost, feasible and scalable approach to monitoring the considerable public-health threat of undetected fentanyl and its analogues in Australia. Further validation of cross-reactivity of test strips would strengthen this method.