"Studies found that DCS [Drug Consumption Services] influenced intended behaviour and, although less researched, enacted behaviour. Among studies of PWUD [People Who Use Drugs] in party settings (referred to as ‘partygoers’ in studies), greater intention to not use the analysed substance was consistently reported if analysis results were unexpected [33, 35, 40, 42, 43, 45, 48, 52] or ‘questionable’/‘suspicious’ [49–51]. For example, a cross-sectional study from Australia (n = 83) in 2018 found partygoers were more likely to change their intention to use when analysis results were unexpected [odds ratio (OR) = 2.63, 95% confidence interval (CI) = 0.85–8.16] , as did two cross-sectional studies from Portugal (n = 310, n = 100) in 2016 and 2014 [40, 43]. Similarly, other intended behaviour changes—such as using less of a substance or seeking more information about it—were more common among partygoers when analysis results from DCS suggested that substances were ‘questionable’/‘suspicious’ [49, 51].
"The proportion of participants reporting analysis results from DCS influenced their drug use varied by population and setting. Among partygoers, 16% of participants in the Netherlands in 1996 , 50% in Austria in 1997–99  and 87% in New Zealand (n = 47) in 2018–19  reported that analysis results impacted their drug use. A cross-sectional study in 2017 from the United States among people who inject drugs (n = 125) found 43% changed their behaviour, and this was more likely when fentanyl was detected [adjusted OR (aOR) = 5.08, 95% CI = 2.12–12.17] . Qualitative and longitudinal studies of young PWUD (n = 81) in the United States in 2017 supported this finding, and found that fentanyl detection was associated with positive changes in overdose risk behaviours (i.e. using less, using with others, doing a test shot) [31, 34]. Overall, and in alignment with findings on intended drug use behaviour in response to ‘questionable’/‘suspicious’ analysis results, self-reported behaviour was more likely to change when analysis results detected fentanyl. Beyond individual analysis results, a repeated cross-sectional study from Colombia (n = 1533) in 2013 and 2016 examined the influence of alerts from DCS and found that a majority of partygoers reported an impact on their behaviour .
"Only one study linked intended behaviours to observed health outcomes for PWUD accessing DCS. A Canadian cross-sectional study of DCS at a supervised injection site (n = 1411) in 2016–17 found that people who inject drugs were more likely to report the intention to use a smaller quantity than usual when fentanyl was detected by DCS (OR = 9.36, 95% CI = 4.25–20.65) . In turn, those intending to use a smaller quantity were found to be less likely to overdose (OR = 0.41, 95% CI = 0.18–0.89) and be administered naloxone (OR = 0.38, 95% CI = 0.15–0.96).
"Disposal of the analysed substance was observed [24, 26, 27, 32, 35] or self-reported [22, 31, 34] as an outcome of DCS in eight studies. Like other behaviours, disposal was more frequent when analysis results from DCS were unexpected [24, 27, 32, 52]."
Maghsoudi N, Tanguay J, Scarfone K, Rammohan I, Ziegler C, Werb D, et al. Drug checking services for people who use drugs: a systematic review. Addiction. 2021;1–13. doi.org/10.1111/add.15734