Intervention
HCV infection
Men in the standard-of-care arm were provided with an educational message and a postcard. The message used concise language to encourage men to be tested for HCV. We invited three CBO leaders and ten community members to create the message and finalized the message based on their feedback. The postcard was developed through a national crowdsourcing contest in China in 2017 with vivid expressions to introduce the risk of acquiring HCV infection, the importance of screening for HCV, and encouragement to conduct HCV testing at local clinics [In addition to the message and postcard for men in the standard-of-care arm, men in the HCV self-testing arm were also provided with HCV self-testing services which allowed them to order a maximum of one HCV self-testing package for free through Wechat during the study period. The HCV self-testing package was sent to men by postal mail (express delivery). The package included the manufacturer-supplied step-by-step pictorial instruction in Chinese (Additional file Study incentives were designed to be similar in the two arms. Participants in both arms were informed at enrollment that costs associated with HCV testing including facility-based HCV antibody testing and self-testing uptake during the study period could be reimbursed by providing a photo of the test report and receipt.