A longitudinal study of a drug checking service for patrons of Boom Festival 2018: behavioral outcomes at individual and group levels.

Drug checking services (DCS) allow people who use drugs to submit drug samples for analysis and receive individualized feedback of results and specialized counseling. Our research aimed at testing the validity of behavioral intention measures against reports of actual behavior after drug analysis and effects of DCS on the adoption of protective behavior strategies at a 6-month follow-up. DCS patrons at Boom Festival 2018 participated in a longitudinal study: pre-drug analysis (N=343);post-drug analysis (n=290); 3-day follow-up (n=195); 6 month follow-up (n=71). Data were analyzed with SPSS 27. Mann-Whitney was used to analyze the influence of gender and age. Fisher's exact tests were performed to determine an association between the test result and the behavior following the test result. Wilcoxon signed-rank tests were used to compare data at pre-test and 6-month follow-up. A two-sided Fisher’s exact test (p<0.001) showed a significant association between the test result, behavioral intention following the test result, and the behaviour reported by users at follow-up. When the result of the analysis was 'not the expected substance,' 86% of respondents reported 'not taking the substance'; 11% reported 'taking a smaller dose than initially planned,' and 3% of the respondents stated they 'took it.' In 71% of the situations where we could match the behavioral intention with the reported behavior at an individual level, the intention matched the actual behaviour. Six months after using the DCS there was a slight increase in adopting most protective behaviour strategies. Our study reinforces the validity of previous research published in this area by addressing the intention–behavior gap, showing that behavioral intention matches self-reported behaviors in most cases. Our findings also suggest that DCS implemented at large-scale music events is a valid harm reduction strategy that helps PWUD make better decisions regarding drug use.