Do needle and syringe programs reduce risky behaviours among people who inject drugs in Kermanshah City, Iran? A coarsened exact matching approach

Introduction and Aims: In this study, we used a ‘coarsened exact matching’ method to evaluate the relationship between two levels of needle and syringe program (NSP) utilisation and HIV-related risk behaviours among people who inject drugs (PWID). Design and Methods: Using snowball sampling, we recruited 500 PWID (all male) in Kermanshah City, Iran between September and December 2014 in a cross-sectional survey. We categorised participants into two groups, including high (i.e. receiving 60 or more of their syringes from an NSP) and low (i.e. receiving less than 60 of their syringes from NSP) NSP users. Then, we applied coarsened exact matching to match the two groups based on confounding covariates (age, place of residence, income, receiving methadone maintenance treatment) and made statistically equivalent comparison groups to estimate the effect of the NSP on injection risk behaviours. Results: Participants with low NSP use were more likely to report borrowing syringes in past 2 months (odds ratio OR 1.71; 95% confidence interval CI 1.30, 1.86; P < 0.04), in comparison with participants with high NSP use. Regarding recent syringe lending, low NSP use was also significantly and positively associated with this outcome (OR 3.34; 95% CI 1.70, 5.20; P < 0.02). Reusing one's own syringe was reported more frequently in low NSP use group (OR 1.40; 95% CI 1.22, 3.97; P < 0.03). Discussion and Conclusions: NSPs are a promising approach to reduce injection-related risk behaviours among PWID in Kermanshah, Iran. Expanded coverage of high-quality NSPs is recommended. © 2017 Australasian Professional Society on Alcohol and other Drugs