Concordance assessment between self-reports of substance use and urinalysis: A population-based study in Mashhad, Iran

Background Few studies have addressed the validity of self-reports of substance use in Iran. This study was conducted to evaluate concordance between self-reported data on drug use and urinalysis results in an adult population in Mashhad as the second most populous city in Iran. Methods This population-based study recruited 2142 Mashhad residents aged over 16 years. The data were obtained from a study conducted in 2015 on the prevalence of chronic kidney disease (CKD) in an adult population in Mashhad. The participants were selected using multistage stratified cluster sampling. To evaluate the validity, the participants' responses to a single-question screening test of drug use were compared with their urinalysis results. The sensitivity, specificity, and positive and negative predictive values of the self-reports were also assessed. Results The prevalence of drug use was found to be 2.33% (95% CI: 1.75-3.09) based on the self-reported data and 17.74% (95% CI: 16.15-19.43) based on the urinalysis results. Opioids were the most prevalent form of drug used and the self-reports indicated low validity (sensitivity = 12.63%, 95% CI: 9.54-16.49). The women were found more predisposed than the men to misreporting their drug use. Discussion In line with other studies in Iran, the validity of the self-reports of drug use was found to be low. Policymakers should therefore avoid relying only on self-reported data to evaluate the effectiveness of interventions and preventive strategies. It is recommended that further in-depth studies be conducted to address the factors affecting the validity of self-reports in Iranian populations.